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Duration modeling with Hidden Markov models ten Bosch, L.F.M.; Wang, X.; Pols, L.C.W.

Publication date 1994

Published in The Journal of the Acoustical Society of America

Link to publication

Citation for published version (APA): ten Bosch, L. F. M., Wang, X., & Pols, L. C. W. (1994). Duration modeling with Hidden Markov models. The Journal of the Acoustical Society of America, 94(3 : 2), 1797 (A).

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Download date:04 Oct 2021 PROGRAM OF

The 126th Meeting of the AcousticalSociety of America

Radisson Hotel ß Denver, Colorado ß 4-8 October 1993

NOTE: All Journalarticles and Lettersto the Editor are peer reviewedbefore publication. Program abstracts,however, are not reviewedbefore publication, since we are prohibitedby time and schedule.

MONDAY AFTERNOON, 4 OCTOBER 1993 TERRACE ROOM, 12:55 TO 4:45 P.M.

SessionlpAO

AcousticalOceanography: Acoustical Determination of Polar Ocean ProcessesI

SubramaniamD. Rajan, Coohair Departmentof AppliedOcean Physics and Engineering,Woods Hole OceanographicInstitution, WoodsHole, Massachusetts02543

James H. Miller, Cochair Departmentof Electricaland ComputerEngineering, Naoal PostgraduateSchool, Monterey, California 93943

Chair's lntroduction•12:55

Invited Papers

1:oo

lpAO1. Fractureof seaice. Ira Dyer (Dept. of OceanEng., MIT, 77 MassachusettsAve., Cambridge,MA 02139) The majorcause of ambientnoise in the Arctic Oceanis radiationfrom the fractureof seaice in responseto environmental forcing.Extant noise data on fracturein packice in the centralArctic and in free-driftingice at its margins,including measures suchas spectraldensity, temporal evolution, and individualice fracturetransients and their statisticsare reviewed.Physical mechanismsresponsible for icefracture are of fundamentalinterest, and thereforethe fracturemechanics of seaice, which leads to a pictureof ice failurenot unlike that of failure in the Earth'scrust via earthquakes,is alsodiscussed. As in earthquakes,ice fracturingis a processof many small fault plane motionswhich can result in a major ice crack. Prospectsfor use of noise measurementsto understandice processesimmediately come to mind, as well as their use intrinsicallyto describeacoustic propertiesof the Arctic Ocean.

1:25

lpAO2. Recentapproaches to the acoustic-seismicstudy of ice mechanics.David M. Farmer and Yunbo Xie (Inst. of Ocean Sci., P.O. Box 6000, Sidney,BC VSL 4B2, Canada)

Acousticand seismicemissions provide useful information on the mechanicalproperties of seaice and its responseto stress. Two recentfield studieseartied out under the ONR Ice Mechanicsinitiative have providedopportunities for exploringthis approachto remotesensing using both passive and active measurements. Passive sensing revealed significant spatial variability in the responseof the ice to thermal stress.Detailed analysis of the acousticsignal in the water yieldsinsight on the source mechanism,which includedlocal uplift, subsequentlyverified by inspectionof the fracture site. Flexural wavesin the ice were anisotropicallydistributed with blockingby a nearbypressure ridge dominating the spatialvariability. Variations in ice properties werealso probed with artificialimpacts on the ice surface,revealing significant variability in both shearand p-wavepropagation. The influenceof the pressureridge was very markedin its attenuationof flexuralwaves, but significantmodifications of shearand p-wavevelocities were also measured. Finally, advantagewas taken of an artificiallyinduced fracture experiment conducted by Dempseyand Spencer in April 1993.Controlled fracturing was induced with a fiat-jackleading to multipleacoustical and seismic

1759 J. Acoust.Soc. Am., Vol. 94, No. 3, Pt. 2, Sept. 1993 126th Meeting:Acoustical Society of America 1759 emissionsthat weredetected with a hydrophonearray. Suchmeasurements should provide a basisfor comparisonwith models for the fractureof heterogeneousmaterials.

l:S0

lpAO3. Oceanographicinferences from ambientnoise in the marginalice zone. Michael J. Buckingham (Marine Phys.Lab., ScrippsInst. of Oceanocr.,La Jolla,CA 92093-0213) In the polarseas the spatialstructure of the ambientnoise is oftendetermined by the upwardrefracting sound-speed profile. Sucha profilesupports normal modes, even in theabsence of bottominteractions. A full theoretical(analytical) model of ambient noisein an inverse-squareprofile--representative of polarwaters--has been developed [Buckingham, Philos. Trans. R. Soc. (in press)],which yields expressions for the auto and crossspectral densities of the noisethat are valid at infrasonicfrequencies (VLF) and low frequencies(LF) up to severalkilohertz. Three termsappear in theseexpressions, representing the modal and continuouscomponents of the noise.When the theoreticalspectra are comparedwith ambientnoise data takenin the marginal ice zone off the east coastof Greenland,a crude distributionof noisesources at the ice edgecan be inferred and bottom effects in the observedspectra become apparent. The spatialinhomogeneity of the noiseis alsovery evidentfrom the theory,which has implicationsconcerning beamforming for obtainingnoise directionality information. [Research supported by ONR.]

2:15

lpAO4. Ultrasoniemodeling of seaice seismoacousticwave phenomena. JacquesR. Chamuel (SonoquestAdvancedUltrason. Res., P.O. Box 153, WellesleyHills, MA 02181-5339)

A variety of broadbandArctic seismoacousticwave phenomenaare demonstratedusing laboratory ultrasonicmodeling techniquesintroduced by the author in the mid 1970sto study the generation,propagation, detection, and scatteringof low- frequencyunderwater acoustic waves coupled to the heterogeneousice cover. Data on frequency-dependentunder-ice reflectivity, effectiveelastic properties, low-frequency transmission loss, horizontal refraction, wave conversion,and low grazing angle backscatteringare discussed.Different guided leaky and trappedwaves from range-dependentmodels are isolatedand examined includingflexural waves, shear horizontal waves, Rayleigh waves,Scholte waves, edge plate waves,and wedgewaves. The laboratorymodels consisted of finitefloating plates with cracks,ridge% low-velocity layers, boreholes, trapped air pockets,solid wedges,and suspensions. The resultsprovide physical insight into realistic 3-D problemsand lead to thedevelopment of comprehensiveunderstanding of near-fieldand long-rangeseismoaconstic phenomena essential for interpretingand inverting Arcticacoustic data, planning field experiments, and predicting ice failure modes from acoustic emission. The genericfindings are applicableto oceanbottom interacting acoustic waves, , and ultrasonic imaging. [Work supportedby DREP and ONR.]

lpAOS. Feasthilityof acousticthermometry of Arctic Ocean climate change. Peter N. Mikhalevsky (Sci. Appl. lat. Corp., Ocean Sci. Group, McLean, VA) Inverting observationsof changesin long-rangeacoustic travel time, phase,amplitude, and modal dispersionhas been proposedfor the Arctic Ocean.Initial calculations[Mikhalevsky et aL, "Arctic OceanWarming; Can We Measureit Aconsti- cally?,"The OceanographicSociety, Second Scientific Meeting, St. Petersburg,FL (March 1991)] showedthat it could be possibleto monitorocean volume warming, and changes is seaice extent and thickness. New resultswill be presentedusing higher fidelityacoustic modeling and the resultsof otherinternational collaborators, including the Russians,will be summarized.Plans for a feasibilitytest in the Arctic are underwayfor a spring1994 experiment.

3.'05-3:15 Break

ContributedPapers

3:15 3:30 lpAO6. Monitoring thermal fracturing in ice: The relation to ice 1pAO7. Acoustical determinationof the ice growth in the Arctic. stressand strength. P. J. Stein (Scientific ,Inc., 47 Aster Henry A. Laiblc (Dept. of OceanEng., MIT, Cambridge,MA 02139 Ct., Nashua, NH 03062), J.K. Lewis (Ariantic Appl. Res. Corp., and Dept. of Appl. OceanPhys. Eng., WoodsHole Oeeanogr.Inst., Long Beach, MS 39560), and W. B. Tucker (U.S. Army Cold Woods Hole, MA 02543) and S. Rajan (Woods Hole Oceanogr. RegionsRes. and Eng. Lab., Hannover, NH 03755) Inst., Woods Hole, MA 02543)

Here observationsof thermallyinduced ice fracturingin the Arctic A crossholetomography experiment was conductedin the Arctic betweenApril 1992 and March 1993 to determine the time evolution of are summarized.Thermally induced fracturesmay be an important the acoustic/elasticproperties of sea ice. Data were taken every third phenomenain understandingice strength.Sets of observationsof event day for 9 monthsusing an array of verticaland horizontaltransducers locationsusing hydrophone and geophonearrays along with meteoro- located in the ice and water column below the ice. A method to monitor logicaland ice stress.measurements are discussed.Data are reviewedfor thegrowth of theunderside of theice consisted of comparingthe arrival both first and multiyearice floes.Stress observations show that smooth timesof boththe directpath and reflected path from transmitters in the firstyear ice can supportmuch higher tensile . The eventlocation water column to the receivers in the water column. The differences in data indicatethat indeedfirst year ice is much lesssusceptible to ther- arrivaltimes over the 9 monthsindicates as much as l-m growthof ice. mal fracturing.This indicatesthat smoothfirst year ice is in some In addition to the ice growth estimates,the reflectioncoefficient was manner strongerthan multiyear ice. determinedas a functionof time and angle.Acoustic characteristics of

1760 J. AcousLSoc. Am., Vol. 94, No. 3, Pt. 2, Sept. 1993 126thMeeting: Acoustical Society of America 1760 the ice in the skeletallayer at the ice/water interfacewas also estimated. 4:15

lpAO10. Relating Arctic ambient noise to thermally induced 3:•5 fracturing of the pack ic•An ability to monitor climate change? lpAOg. Measurement of large scale deformation of the Arctic ice J'amesK. Lewis (Atlantic Appl. Res. Corp., 207 S. SeashoreAve., pack usingacoustic backscatter. Greg Duckworth,Kevin LePage, Long Beach,MS 39560) and Ted Farrell (Bolt Beranek and Newman, Inc., 70 Fawcett St., Cambridge,MA 02138) Thermallyinduced fracturing of packice can be simulatedusing a visc.oelastic model and a fracturingparadigm for predictingthe stress The ONR AEAS Programsponsored a low-frequency reverberation state of the ice. Under a given set of circumstances.the fracturing studyprogram in the Central Arctic as part of the AREA-92 Exercise paradigmsimulates conditions that exceedthe tensilestrength of the ice in March-April of 1992.The ZIRCON ice camp was the site of the as well as the associatedstress relief as a result of fracturing.The monostaticand bistaticactive experiment with acousticsources, a thermal stress-icefracturing model was used to producea fracture 256-channelbillboard receive array, and real-timeprocessing and dis- counttime historyfor the ice packduring the fall of 1988in the eastern playsystem. The reverberationdata collected have been coherently pro- Arctic Ocean.The countwas compared to the observed500-Hz under- cessedbetween sequential pings to estimatethe bearing,range, and ice noisein which 13 distinctnoise episodes were identified. The simu- radialvelocity of ice scatteringfootprints of variousrange and bearing lation showedincreases in predictedfracturing !eveis for 11 of the 13 extents.Due to the highly repeatablenature of reverberationfrom the noiseepisodes. Some of the fracturingwas associated with nightlycool- ice canopy,high sourcestrength, and the gain of the receiverarray, this ing. Othersoccurred as a resultof sustainedcooling over severaldays processingis shownto be capableof unambiguouslyestimating the followingthe passageof coldfronts. The stress-fracturingmodel can be movementof thesefootprints over a 250-kin-radiusarea to betterthan usedto studychanges in under-icenoise as a resultof globalwarming. 10-maccuracy for transmissionsasfar apartas 4 h. Strainrate estimates Examplesare presentedbased on warmingas predictedby variouscli- usingthe technique agree with sparse GPS data in thearea covered, and matemodels. The resultsindicate that climatechanges could be moni- are shownto be well modeledby a simplethree-parameter strain rate tored usingwinter-time under-iceambient noiseobservations from the field.The detailsof the outputfrom the processingalso shed light on the Arctic. fundamentalacoustic propagation and backscatterprocesses them- selves.[Work supportedby ONR.]

4:30

lpAOll. Oceanological aspects of acoustic monitoring of Arctic 1pAO9. Arctic ambient noise and climate change. Warren W. Ocean elimate. K. D. Sabinin (N. N. AndreyevAcoust. Inst. and Denher (EOS Res. Associates,P.O. Box 1378,Carmel Valley, CA Ocean Acoust. & Inform. Ltd., 38 Vavilov St., Moscow, 117942, 93924) Russia)and S.V. Pisarev (StateOceanogr. Inst. and OceanAcoust. In globalwarming, sea ice playsa significantrole, and seaice con- & Inform. Ltd., Moscow, 117942, Russia) ditionsmay provideone of the mostsensitive parameters to monitor. Modelingpredicts that warmingwill begreatest at highlatitude, and sea The Arctic Ocean is an importantobject of investigationin the iceproperties are very sensitive to warmingand changes in atmospheric globalATOC programbecause of its crucialrole in the heat balanceof forcing.Therefore, sea ice mightprovide a sensitivemarker for climate the Northern Hemisphere.Although the temporaland spatialvariabil- change.The mechanicalproperties of sea ice are relatedto the ice ity of the soundspeed in the Arctic Oceanis relativelyweak, the Arctic ,salinity, thickness,, and flow size distribu- ice coveressentially complicates modeling of the acousticresponse to tion. It hasbeen established that the ambientnoise field under pack ice climatechange. Moreover, the influenceof the stronglyvarying ice is correlatedto the mechanicalproperties, ice conditions,and forcing. cover causesadditional difficulties in interpretationof the resultsof Many studiesover the last two decadeshave delineatedsome of these acousticocean thermometryfor severalreasons: (1) the extremely relationships.The hypothesisof this paperis that monitoringthe am- stronginfluence of ice distributionon the ocean-atmosphereheat ex- bientnoise under the ice,for whichthere is well-developedand reliable change,(2) the long-termvariation of the icecover, and (3) thespecific technology,may be an excellentway to detecta climatechange signal. responseof the surfacewater sound speed to heatingof an ice-covered This paperwill reviewthe relationshipsbetween under ice ambient noise sea (a heat input shoulddecrease the soundspeed under melting ice). and the propertiesof the ice pack.Based on what is known,a monitor- Under-icewinter convection can alsocreate specific kinds of inhomo- ing systemconsisting of remotelyoperated buoys is proposed.A pro- geneitiesof the Arctic Ocean (chimneys,plumes of densewater, etc.). posedbuoy design and samplingarray for the Arctic is presented.Used Additional seriousdifficulties arise becauseof strong dependencyof in conjunctionwith satelliteremote sensing, the?ystem could provide Arctic climate on the heat inflow of both the Atlantic and Pacific for continuousmonitoring of the ice packfor otherpurposes and would Oceans.This changeableinflow can causelong-term variations of the be costeffective for acousticmonitoring of the climatechange signal in Arctic Ocean.It seemsworthwhile to beginthe Arctic ATOC with the the Arctic. installation of acoustic tracks across the Fram Strait.

1761 J. Acoust. Soc. Am., VoL 94, No. 3, Pt. 2, Sept. 1993 126th Meeting: AcousticalSociety of America 1761 MONDAY AFTERNOON, 4 OCTOBER 1993 MAJESTIC BALLROOM, 12:30 TO 5:00 P.M.

SessionlpSP

SpeechCommunication: Models and Mechanismsin SpeechProduction

Ronald C. Scherer, Chair TheDenver Center for thePerforming Arts, 1245 ChampsStreet, Denver, Colorado 80204

ContributedPapers

12'.30 A physicalmodel of a vocalfold wasconstructed with threelayers: an artificialepithelium (latex), a superficialReinke's space (water), IpSPI. Voice simulationwith n three-massmodel of the vocal folds. and an immobile vocal fold body (aluminum). This vocal fold was Brad H. Story and Iago R. Titze (Natl. Ctr. for Voice and Speech, positionedin a plexiglasairway suchthat the glottalaperture and the Dept. of SpeechPathoi. and Audiol., Univ. of Iowa, Iowa City, IA convergenceangle could be variedsystematically with respectto a solid 52242) boundary,which representedthe oppositevocal fold in a hemilarynx The classictwo-maas model of the vocalfolds [K. Ishizakaand J. L configuration.Subgiottal was controlled with a constantpres- sure valvingsystem. Phonatioa threshold pressure (the Hopf bifurca- 1 lanagan,Bell Syst. Tech. J. 51, 1233-1268(1972)] hasbeen extended tion in nonlineardynamics) was measuredas a functionof glott•l al• to a three-massmodel in order to representmore accuratelythe body- cover vocal fold structure [M. Hirano, Folia Phoniat. 26, 89-94 erture and divergenceangle. This pressureincreases with increased (1974)].The modelconsists of two "cover"masses that arecoupled to apertureand convergence,as predictedby theory,but resultsfor a a "body"mass by nonlinearsprings and viscous damping elements. The divergentglottis are not as easyto interpret.[This researchwas sup- bodymass, which represents muscle tissue, is alsocoupled to a rigid portedby Grant No. P60 DC00976 from the National Instituteon Deafnessand Other CommunicationDisorders.] wall (assumedto representthe rigid laryngealframework) by a non- linearspring and damping element. The two coversprings are intended to representthe vocalligament tension while the bodyspring simulates 1:15 the tensionproduced by contractionof the thyroarytenoidmuscle (TA). Additionallythe two cover massesare coupledto each other lpSP4. Noninvasive phonation threshold pressure estimates: Some througha linearspring that can be regarded as representing the surface methodologicalconsiderations. Kimberly Fisher (Univ. of Oklahoma tensionof the coverand hencelargely contributes to the mucosalwave Health Sci. Ctr., 825 N.E. 14th St., OklahomaCity, OK 73190) velocity.Effects on the vocalfold movementdue to changesin subglot- tal pressure,spring tensions, clement masses, and vocaltract loading Phonation thresholdpressure (PTP) is the minimum subglottal will be shown. pressurerequired to initiatevocal fold oscillation.This pressureis im- portantboth theoreticallyand clinicallybecause of its relationshipto tissueviscosity, time varyingglottal flow, and vocaltract acoustics.The 12:48 effects of several different measurement methods on estimated PTP were studied in normal subjects.Oral pressuresduring quietly voiced IpSP2. Analysis of rough voice from a nonlinear dynamicspoint of consonant-vowel-consonantsyllable strings were usedto estimatePTP. view. David A. Berry, Ingo R. Titze (Natl. Ctr. for Voiceand Speech, Factorsexpected to impact PTP estimatesincluded: ( l ) low nasalflows Dept. of SpeechPathol. and Audiol., Univ. of Iowa, lows City, IA asscciatedwith soft, relaxedphonafion, and (2} vowel context, due to 52242), and HanspeterHerzel (Humboldt University,O-1040 Berlin, possiblereactive loading. A significantpercentage of normal subjects Germany) evidencedlow, inconsistentnasal airflow during /p/ occlusionnear threshold(as indicatedby nasalpneumotachography). Nasal flow was Becausethe vocalfolds are nonlinearsystems with manydegrees of not associatedwith supra-thresholdproduction for thesesame subjects. freedom,bifureafions and chaosshould be expectedfor certainparam- In spiteof similarinstruction and pre-recordingpractice, subjects varied eter configurations.Indeed, bifurcations and chaosappear in someof in the strategiesthey usedto accomplishphonation at soft levelsnear the simplestmodels of vocalfold vibration.They are alsoseen in more their thresholdpressure. Strategics potentially involving slight adjust- complexmodels, in modelsthat incorporateleft-fight asymmetries,and mentin giottaladduction were observed and would be predictedto alter in biomechanical simulations of vocal fold oscillations. Furthermore, an PTP. Thesemethodological challenges will be discussedrelative to the acousticalanalysis of many types of rough voice (e.g., creaky voice, variabilityo•'•erved in PTP estimates,and the potentialimpoct on va- vocal fry, and newborninfant cries} revealsan intimate relationship lidity and reliabilityof noninvasiveoral pressuremeasurement. betweenvoice mechanics and bifurcatioosand chaos.Likely physiolog- ical mechanismsof the observednonlinear phenomena are presented. Basicconcepts and analysistechniques from nonlineardynamics are 1:30 reviewedand comparedwith traditional voiceanalyai• •ehemea. Finally, it is shownhow much of the terminologyin the literature describing lpSP5. Laryngcal rcsistaneeof an in vivo canine model of phonation roughvoice can be unifiedwithin the frameworkof nonlineardynamics. with a constantair pressure•o uree. Sina Nasfi, Ali Namazie,Ming [This researchwas supportedby Grant. No. P60 DC00976 from the Ye, Joel A. Serearz, Jody Kreiman, Bruce R. Gerratt, and Gerald S. National Institute on Deafnessand Other CommunicationDisorders.] Berke (Div. of Head and Neck Surgery,UCLA Schoolof Medicine, 10833Le Conte Ave., Los Angeles,CA 90024-1624) Previousstudies of laryngealbiomechanics using in oivomodels have generallyused a constantair flow source.Several authors have recently lpSP3. Phoa•ion thr--•hold pressurein a physical model of the vocal suggestedthat duringphonation, the lung-thoraxsystem functions as a folds. Iago R. Titze and Michael R. Titze (Natl. Ctr. for Voice and constantpressure source. The presentpaper describes an in oioocanine Speech,Dept. of SpeechPathoL and Audiol., Univ. of Iowa, Iowa City, systemdesigned to maintaina constantpeak subgiottic pressure (Psub) IA 52242} usinga pressure-controllingmechanism. It was found that with a de-

1762 J. AcousLSoc. Am., Vol. 94, No. 3, Pt. 2, Sept. 1993 126th Meeting:Acoustical Society of America 1762 crease in P•.b, the range of recurrent laryngeal nerve stimulation speechdisorders, that is, individualswith "normal"voices. Any diag- (RLNS) voltageneeded to inducephonation was reduc,ed. At a given nosticvalue thesemeasures might have requiresthat one studiesthe superiorlaryngeal nerve stimulation (SLNS) leveland Psub,increasing characteristicsof these "normal" voice distributions,in particular the levels of RLNS resulted in a normal distribution of vocal efficiencies. quantilesnecessary to establishthe normal range. The focuswill be on For eachSLNS and Psub, minimum and maximum levels of RLNS were perturbationsmeasures, such as jitter andshimmer. To solvethis prob- determinedoutside of which no phonationwas possible.Levels of lema methodof importancesampling has been developed for estimating RLNS that producedan optimalstable phonation were also identified. quantilesof skeweddistributions. Importance sampling is a modified Increasinglevels of RLNS resultedin significantdecreases in glottalair bootstrapprocedure with exponentialtilting, that is, a resampling flow. Contraryto a previousreport usinga constantflow source,in- methodwhere the probabilitiesof the originalobservations appearing in creasinglevels of SLNS produceda significantdecrease in glottalresis- the new samplesare no longerequally weightedbut are weightedby tance.This is consistentwith anotherprevious study [D. M. Mooreand their closenessas an order statisticto the quantilebeing estimated. To G. S. Berke,J. Acoust.Soc. Am. g3, 705-714 (1988)] demonstrating estimatethe normal limits of jitter and shimmerwithout resampling that the openquotient increased with increasingSLNS. procedureswill requireat least800 subjects.However, to estimatethe normal limits with the sameefficiency using this modifiedimportance samplingtechnique will requireapproximately 80 subjects.The assess- 1:45 mentof voiceis veryexpensive and time consuming. There will neverbe lpSP6. A study of pulaatile airflow in the exeiaed larynx model. 800 normal voice assessmentsconducted under identical conditionsby FariborzAlipour (Dept.of SpeechPathol. and Audiol., Univ. of Iowa, anyone.How modifiedimportance sampling can be usedto establish Iowa City, IA 52242-1012)and Ronald C. Scherer (Denver Ctr. for normal limits for jitter and shimmerwill be demonstratedwith data the PerformingArts, Denver, CO) collectedat the Denver Centerfor the PerformingArts, Denver,Colo- rado, and the WendellJohnson Speech and HearingCenter, University The pulsatileairflow in the excisedlarynx was investigated with the of Iowa, Iowa City, Iowa. simultaneousmeasurements of glottalpressure, volume flow, EGG, and particlevelocity at variousdynamic conditions of the larynx. Canine laryngeswere mountedin a benchwith somesutures attached to car- 2:30-3:00 Break tilagesto mimicthe functionof laryngealmuscles. The sustainedoscil- lations were obtained and maintained with the flow of heated and hu- 3:00 midifiedair throughthe trachea.The pitchand amplitude of oscillations werecontrolled with amountof airflowand the mechanicaladjustment IpSP9. Speechproduction: Thirty years after. Arthur S. House of glottaladduction and vocal-fold elongation. The particlevelocity was (IDA Ctr. for Commun. Res., Princeton,NJ 08540) and Kenneth measuredabove the glottiswith a constanttemperature hot-wire probe N. Stevens (MIT, Cambridge,MA 02139) at variouslocations and oscillating conditions. The measuredsubglottal pressurewith a pressuretransducer had a periodicvariation and its Measurementshave beenmade on a corpusof bisy]labicnonsense meanvalue was higher than the manometer'sreading of the sameloca- utterancesspoken by threeadult maletalkers on two occasionssepa- tion. The measuredparticle velocity showed some turbulence superim- ratedby 30 years.The 1960and 1990recordings were processed simi- posedon a periodicflow. The mcanparticle velocity showed some vari- larly so that comparisonscould be madedirectly. Some primary and ationsin the glottalexit areaboth along the vocalfolds and acrossthe secondarycharacteristics of vowelswere measured:duration, funda- glottis.[•/ork supportedby NIDCD Grant No. DC00831-02.] mentalfrequency and the frequenciesof F1 and F2. The durationsof prestressedconsonants were measured, and vowel-consonant amplitude ratioscomputed. Long-term spectra of the talkerswere examined and 2:00 someinformal listening comparisons were made. Spectrograms of some sampleswere studied, and statisticalanalyses, when appropriate, were lpSP7. The effect of gas densityon glottal vibrationand exit jet made.Results indicate that the talkers'productions were remarkably particle velocity. Steven Bielamowicz,Gerald S. Berke, Jody consistentover 30 years.Over time the talkers'mean vocalic duration Kreiman, Bruce R. Gerratt, David C. Green (UCLA Div. of Head (10 vowels) shortened(6 ms); their mean vocalic fundamentalfre- and Neck Surgery,UCLA Schoolof Medicine, CHS 62-132, Los quencyrose (7 Hz); theirmcan frequencies ofFI andF2 (10 vowels) Angeles,CA 90024and VA Med. Ctr., WestLos Angeles,CA 90073), descended(15 and 26 Hz, respectively);their mcan (initial) fricative and Richard S. McGowan (Haskins Labs., New Haven, CT 06511) durationlengthened (12 ms); and, their mean (initial) stopduration Althoughtheoretical studies include a term for gasdensity in their lengthened(hold portion,15 ms;release portion, 5 ms). Interactions mathematicaldescriptions of glottal aerodynamics,no studieshave wereusually significant: individual talkers' changes in duration,formant measuredthe effectof gasdensity on glottalvibration and particleve- frequencies;and fundamental frequency were not identical.Patterns of locity.This studyused a constanttemperature anemometer in the in durationand fundamental frequency in the setof vowels,however, were vivocanine model of phonationto evaluatethe effectof gasdensity on stable over time. subglotticpressure, particle velocity, and glottal vibration by comparing

phonationwith air andhelium. With gasflow and laryngeal nerve stim- 3:15 ulationheld constant, peak subglottic pressure was significantly greater duringhelium phonation (70 cmHg) thanduring air phonation(62 cm lpSP10. Motor equivalencein the transformationfrom vocal-tract Hg). In addition,peak particle velocity during helium phonation (45 configurationsto the acoustictransfer function:Adaptation to a bite m/s) wassignificantly greater than phonationwith air (34 m/s). How- block. J. S. Perkell, M. L. Matthies, M. A. Svirsky, and M. I. ever,the increasein particlevelocity with heliumcompared to air was Jordan (SpeechCommun. Group, Res. Lab. of Electron., MIT, lessthan predictedby the Bernoullirelationship. This lossin velocity Cambridge, MA 02139) likely representsturbulent and frictionalforces at the glottaloutlet. In a preliminarystudy [Perkell et al., J. Acoust.Soc. Am. 93, 2948 (1993)] subjectsdemonstrated a tradingrelation (negativecorrela- 2:15 tions)between tongue-body raising and lip protrusionin productionof the vowel/u/. Data analysesindicated an increasedtendency for the 11•qPS.The role of importancesampling in the establishmentof tradingrelation to occurat highvalues of F2. Thetentative hypothesis normalranges for speechcharacteristics. .Ion H. Lemke and Hani is that when more than one articulator contributes to producing a par- . Samawi (Dept. of PreventiveMed. and Environ. Health, 2800 tieular acousticcue and a sourceof variationdisplaces one of the artic- SteindietBldg., Univ. of Iowa, Iowa City, IA 52245) ulatorsaway from its target,compensating (complementary) adjust- Most measurementsof voice characteristicshave inherently skewed ments are made in the programmeddisplacements of the other distributionsthat have never been characterized for individuals without contributingarticulator(s) to help constrainthe acousticvariation.

1763 J. Acoust.Soc. Am., Vol. 94, No. 3, Pt. 2, Sept. 1993 126th Meeting:Acoustical Society of America 1763 Theseadjustments should be morestrongly expressed in tokensthat are Elliot Saltzman (Haskins Labs., 270 Crown St., New Haven, CT closeto phonemicboundaries, where variationin the displacementof 06511) one of the contributingarticulators could resultin productionof the wrong sound.This work has been extendedwith two new subjects. To examinethe mappingfrom acousticsto articulation,simulta- neousartieulatory and acousticmeasurements were made of 90 vowel- halfwaythrough the experimenta bite blockwas placed in the subject's mouth to introduce an additional source of variation. One subject to-voweltransitions produced by a Swedishspeaker. Artieulator posi- strictly usedcoordination (i.e., positivecorrelation) to produce/u/and tionswere measured using an electromagneticmidsagittal articulometer that trackedseven receiver coils placed on the lips,jaw, and tongue.The did not alter this strategywith the bite block.Negative correlations were foundfor the othersubject in subsetswith relativelyhigh values of F2. vocal tract transferfunction associatedwith each articulator position [Work supportedby NIDCD.] wasestimated using cepstral analysis on shortwindows (25.6 ms) of the acousticsignal. The transferfunctions were then vectorquantized, giv- ing each articolatorconfiguration a correspondingvector quantization 3'.30 code.Given an acousticsignal and its correspondingvector quantiza- tion code(code I for example),an estimateof the positionof any coil IpSPII. Formantsensitivity in the vocaltract. SungbokLee (Central during the productionof a speechsignal can be madeby averagingall Inst. for the Deaf, glg S. Euclid, St. Louis, MO 63110) the positionsthe coil assumedduring the productionof soundslabeled Sensitivityof formantsto perturbationsof the locationand degreeof with vectorquantization code 1. This producesa codebookthat allows tongue constrictionwas studied.These two tongue parameterswere artieulatorpositions to be estimatedfrom acousticsignals. On a data set extractedfrom vowel-like midsagittaltongue shapes (•V=321) gener- not usedfor training,correlations between estimated and actual receiver ated usinga tonguemodel [Harshmanet at, J. Acoust.Soc. Am. 62, coil positionsvary stronglywith the placeof attachment,but correla- 693-707 (1977)]. The tongueshape data were arrangedsuch that the tionsabove 0.9 are commonfor coilson the tongue.[Work supportedby tongueparameters vary morttonically.Lip openingwas varied from 0.3 r4IH.] to 6.0cm 2 in 0.3-em2 steps and the first three formants of eachvocal tract werecomputed. Formant sensitivity was evaluated as dF/dA {Hz/ 4•15 mm), whered/l is perturbationin a tongueparameter and dF is the correspondingformant change,and was plottedas a functionof the IpSPI4. Duration aspects in manner of articulation distinctions. locationof tongueconstriction. The resultscan be interpretedin terms JoaquinRomero (Haskins Labs., 270 Crown St., New Haven, CT of the formant variability,or stability,of a givenvocal tract configura- 06511) tion. One findingis that at the tongueposition associated with the vowel Differencesin mannerof articulation---betweenstops, fricatives, and /u/the formants are very stable under perturbationof the location of approximants•bavebeen describedarticulatorily in terms of degree constriction.However, the sameposition is found to be the mostunsta- and area of the constriction.It is suggestedhere that suchdifferences ble positionfor both F2 and F3 under perturbationof the degreeof are generallyaccompanied by a distinctionin the duration of the con- constriction.This may explainthe largestF2 and F3 variationsof/u/ strictiongestures. An experimentwas carriedout in which an optical in a set of normalizedproduction data of vowels[Syrdal and Gopal, J. trackingdevice was used to recordthe movementof the lipsof a speaker Acoust. SOC.Am. 79, 1086-1100 (1986)]. [Work supportedby of AndalusianSpanish, a dialectspoken in SouthernSpain that has a NIDCD, DC 0O296.] completeseries of hornorganicstops, fricatives, and approxirnants.Re- suitsof both acousticand kinematicanalyses indicated that, while cer- 3:48 tain variationin constrictiondegree was indeed observed, the durational differencesappeared to be much more stable and robust. A bilabial lpSPI2. Gradation of jaw perturbationeffects on mandibular,labial, frieative[B] not only hasa narrowerconstriction than an approximant and velar kinematics. H. Betty Kollia (City Univ. of New York, New ,/•but is also longer. Fricatives, because they need to generate turbulent York, NY 10036 and Haskins Labs., 270 Crown St., New Haven, CT airflow,have a longer,more precise articulatory configuration than O651O) proximants,which create no turbulenceand, consequently,need not remainin a particulararticulatory configuration for long. Becauseof It was recentlyshown that anatomicallylinked and remotearticu- latorssuch as the jaw, the lips, and the velum are functionallycon- theirvery short duration, approximants seem to lacka precisearticu• latory target:they showa greatdeal of variationin their articolatory strainedduring bilabial closing, exhibiting temporal stability in the pat- ternsof interarticulatorycohesion [Ko!lia et at, J. Acoust.SOc. Am. 92, trajectoriesand are verysensitive to coarticulationfrom neighboring segments.[Work supportedby NIH Grant Nos. DC.-00121and HD- 2390 (A) ( 1992)].Further, it wasfound that, whenfunctionally related 01994 to HaskinsLaboratories.] for speech,jaw, lips,and velumshow compensatory kinematic adjust- meritsto a mechanicaljaw perturbation,such as increasedmovement displacementand oral closingvelocity, thereby maintaining interartic- ulator cohesion [Kollia et aL, J. Acoust. Soc. Am. 91, 2474 (A) (1992)]. The interpretationis that speechmovements are controlledin IpSPI$. The 3-D-tongue FEM model revised. Reiner a globalmanner, rather than independently,reflecting large scale vocal Wilheims-Tricarico (ATR International, Kyoto, Japan) and tract actions.The presentstudy aims at untanglingthe gradienteffects Cbao-Min Wu (Biotaed. Eng. Ctr., Ohio State Univ., Columbus,OH of the perturbationon the arfieulatorsand their kinematicparameters. 43210-1002) Overall load effectsdepended on the distanceof the artieulatorfrom the As a first applicationof a newly developedobject-oriented finite siteof the perturbation.Load effects were heightened in structuresthat elementcode that is specialized for themodeling of biologicaltissues we were more proximal to the perturbationsuch as the jaw and the lower have been reimplementingthe geometryof the tongue model by S. lip, anddiminished in moreremote structures, such as the upperlip and Kirtani et al. ("A computationalmodel of the tongue,"Ann. Bul. Res. the velum.Moreover, load effects depended on the loadonset time and Inst. of Logopedicsand Phoniatrics,Univ. Tokyo, Vol. 10, pp. 243- had a variableeffect on the differentkinematic parameters. [Work sup- 251). Thenew implem, entation uses large strain and dynamic modeling ported by NIH Grant Nos. DC-00121 and DC-00594 to Haskins Laly of the tissue,includes the effectsof inertiaand observes precisely a weak oratories.] formulationof the incompressibilityconstraint of the tissue.The muscle activationinput for the currentmodel is madesimilar to the original 4.'00 computation. However, a different, more realistic nonlinear muscle modelis used,in whichthe activestress depends on the instantaneous lpSPI3. Inferring artieulator positions from acoustics: An strainand strain rate in thedirection of the musclefibers. The imple- electromagneticmidsagittal artieulometer experiment. John Hogden, mentationmethods and computational results will bepresented. [work Anders Lofquist,Vincent Gracco, Kiyoshi Oshima,Philip Rubin, and supportedby the WhitakerFoundation and by ATR-International.]

1764 d. Acoust.Soc. Am., Vol. 94, No. 3, Pt. 2, Sept. 1993 126thMeeting: Acoustical Society of America 1764 4:45 sustainedpronunciation of nasalconsonants. A marked morphological differencewas observedbetween these data and the previousdata par- IpSPI6. MR! measurementsand acousticinvestigation of the nasal ticularlyin the middleportion of the nasaltract. The previousdata andparanasal cavities. JianwuDang, KiyoshiHonda (ATR Human measuredfrom cadaverspecimens have a wide cavityin the middle InformationProcessing Res. Labs., 2-2 HikaridaiScikacho Soraku-gun, portionpossibly due to absentor alehydratedmucous membrane, while Kyoto, 619-02Japan}, and HisayoshiSuzuki (ShizuokaUniv., 3-5-1 thesedata show narrow passages caused by thick mucosa.It wascon- Jouhoku,Hamamatsu, 432 Japan} firmedby an experimentthat the abovedifference was reproducible by Morphologicalmeasurements of the nasaland paranasalcavities applyingan adrenaline-likeagent onto the nose.The acoustictransfer were performedto speculateon the acousticproperties of the human function was calculatedfrom thesedata, and the speechsound, recorded nasal tract. The magneticresonance imaging (MRI) techniquewas soon after MRI scan, was used to evaluate the transfer function. The used to measure the three-dimensional structure of the vocal tract. The resultsindicate that the asymmetryof two nostrilscan causean extra area function of the nasal tract was calculatedfrom sevensubjects at pole-zeropair, and suggestthat the paranasalcavities can play an im- rest. The whole vocal tract was measuredfrom five subjectsduring portantrole in shapingspectral characteristics of humannasal cavities.

MONDAY AFTERNOON, 4 OCTOBER 1993 COLUMBINE ROOM, 12:55 TO 4:15 P.M.

SessionIpUW

Underwater Acoustics:Scattering and Reverberation I

Dale D. Ellis, Chair SACLANT UnderseaResearch Center, Viale San Bartolomeo400, 19138La Spezia,Italy

Chair's Introduction--12:55

Contributed Papers

1:00 and they generallysupport the approximateanalysis of P. L. Marston et aL (Abstract 4pSA2 at this meeting).For a suitablycut randomly IpUWl. Scattering from under-ice features and estimation of ice orientedplate, the retroreflectiveenhancement is morelikely to be ob- roughnessparameters. Tarun K. Kapoorand Henrik Schmidt (Dept. servedthan the specularreflection since then the normalmust lie on a of OceanEng., MIT, Cambridge,MA 02139) narrowrange of angles. Previousresults by Kapoorand Schmidt[J. Acoust.Soc. Am. 93, 2419 (A) (1993)] haveshown the possibilityof isolatingscattering hot 1:30 spotsunder the ice sheetby matched-fieldprocessing of short-range returnsassuming point scatterers. A naturalextension of thisapproach lpUW3. Long-rangemeasurements of the strength and spectral is to modelthe scatteredfield, or replicafield, assuming a morerealistic characterof low-frequencysurface reverberation. Roger C. Gauss, modelof the scatterers.Here, examinationof the low-frequencyseat- Raymond J. Soukup, David M. Fromm (Naval Res. Lab., teringdata from the CEAREX 89 fieldexperiments conducted in the Washington,DC 20375-5350),and JosephM. Fialkowski (Planning CentralArctic regionwith 1.8-1bSUS chargesdetonated at nominal Systems,Inc., McLean, VA 22102) depthsof 800ft is continued.The beamformeroutputs from the crossed horizontalarray and verticalline arraysare combinedsimulating a Long-rangemonostatic measurements of low-frequency(185-985 volumetricarray, which providesmuch better resolutionof the under- Hz) and low-grazing-angle(nominally 5-15 deg) acousticsurface scat- ice features.The scatterersare modeledas hemisphericaland half- teringwere made in the Gulf of Alaskain Februaryof 1992.The cylindricalprotuberances. Importance of elasticproperties of the ice upward-refractingsound-speed profiles permitted ensonification of the andthe protuberanceswill be addressed.Ice roughnessparameters are seasurface at rangesof severaltens of kilometerswithout interacting estimatedusing the method of smallperturbations. [Work supported by with the oceanbottom. Reverberationreturns from theseranges were ONR.] usedto quantifyboth the strengthand spectralcharacter of surface/ near-surfacereverberation as functionsof frequencyand environmental 1:15 conditions.Spectral results over the rangeof wind speeds(4-17 m/s) haverevealed a dominantzero-Doppler component and a weaker-than- lpUW2. Retroreflectivebackscattering of sound in water due to expecteddependence of spreadon both wind speedand frequency. l-arab waveson plateswith corners:Observations. S.S. Dodd, C. Overall,the resultsare consistentwith sub-surfacebubbles as the driver M. Loeffler,and P. L. Marston (Appl. Res. Lab., Univ. of Texas, for surfacereverberation when whitecaps are present,and will provide Austin, TX 78713-8029) data for comparisonwith theoreticaland numericalmodels, which in turn will giveinsight into thephysical mechanisms responsible for the A leakyLamb wave is known to belaunched on a flatelastic surface observedacoustic scattering. [Work supportedby SPAWAR (PMW- platein waterwhen the surface normal lies near a conewhose symmetry 182) and ONR (Code4532).] axisgives the k vectorof the incidentsound. These water tank experi- mentswith a 600-kHz sonardemonstrate that when the plate has a cornerwith edges meeting at anglesof 90ø and 45 ø , the wavevector of 1:45 the Lamb wave is reverseddue to repeated reflectionsat the edgesthat form the corner. The resultingleaky radiation givesa pronounceden- IpUW4. Measurementsof ocean surface and bottom backscattering hancementof the backscatteringthat dependsonly weaklyon the ori- strengths in the northwestern Atlantic Ocean. Nolan R. Davis, entationof the corner.Reductions in amplitudewith deviationsof the JosephJeffcry, and Fred T. Erskine (Acoust.Div., Code7142, Naval cornerangle from 9(Y' and with tiltsof the surfacenormal were observed Res. Lab., Washington,DC 20375-5350)

1765 J. Acoust.Soc. Am., Vol. 94, No. 3, Pt. 2, Sept. 1993 126th Meeting:Acoustical Society of America 1765 Experimentalmeasurements of ocean surfaceand bottom back- 2'.3O scatteringstrengths were earfled out in the northwesternAriantic lpUW7. BacksraRer from gas bubbles in muddy sediments. Frank Ocean during July and August of 1990. The experimentused ship- A. Boyle and NicholasP. Chotiros (Appl. Res. Labs.,Univ. of Texas, deployedexplosive charges to provideensondication of the oceansur- Austin, TX 78713-8029) face and bottom over a rangeof low frequenciesup to I kHz. Overall the surfacescatter results agreed well with the Ogden-Erskinecurves, Recentexperimental evidence suggests that trappedgas bubbles may matchingthe predicteddependence on wind speed,grazing angle, and be dominant in backscatterfrom sandy sediments.A model basedon frequency.At two sitesnortheast of the Grand Banksthe surfacescat- scatteringfrom a spatialdistribution of resonantbubbles was previously teringstrengths appeared to be dominatedby volumescattering due to usedto predictshallow grazing angle backscatter from sandysediments fish. The bottom scatteringstrengths were observedto have consider- IF. A. Boyleand N. P. Chotiros,J. Acoust.Soc. Am. 93, 2397 ( 1993)]. ablevariation in level (up to 16 dB} betweendifferent sites. As a func- A similar model is developedfor predictingbackscaRer from muddy tion of grazingangle, most of the bottomscattering strength curves sites.The sedimentgas fraction is treatedas a free parameterin fitting paralleledthe Mackenzie curve for grazingangles between 20 • and40'. modelpredictions to measuredbackscattering strengths. Model predic- A moderatefrequency dependence of less than 3 dB was observed. tionsare comparedwith experiment.[Work supportedby NRL/SSC.] Comparisonsof the bottomscattering strengths with the Damuth 3.5- kHz echo-characterprovince types yielded no consistentcorrelations. 2:45-3:00 Break Comparisonswith archivalresults for the sameregion yielded general agreementwithin 6 dB. Comparisonof the ship-basedand airborne techniquesshowed that theyyielded camparable scattering strengths to 3:00 within $ dB. lpU'vVS. Azimuthal variation of low-frequencyBragg scatteringfrom the ocean surface. C. S. Hayek, I. W. Schurman,C. A. Boyles,and J. H. Sweeney (The JohnsHopkins Univ., Appl. Phys. Lab., Johns 2.'OO HopkinsRd., Laurel, MD 20723-6099)

IpUWS. High-resolution beam spectra of forward surface scattered Low-frequencysound, backscattered from an annulusof oceanap- signalsin shallowwater. Yung P. Lee and CharlesW. Spofford (SCI. proximately9 km wide at a nominal 43-km range, was measuredon a Appi. Intl. Corp., 1710 Goodridge Dr., MS TI-3-5, McLean, VA 128-hydrophonehorizontal line array (HI.A) during an experimentin 22102) the Gulf of Alaska.Fourier analysis of the backscatteredsignal permit- ted separationof the Bragg-shiftedreturns from the 250-Hz carrier A shallowwater experimentwas conductedto examinethe direc- frequency.The Bragg-reflectedenergy was resolvedin azimuth by tionalityand spectralspread of cw signalsafter multipleinteractions beamformingthe HLA data. Azimuthally varyingsea surfaceback- with the sea surface.Bottomed sources with frequenciesbetween 200 scatteringstrengths, carresponding to measuredwind speeds,were ob- tainedusing an exactsolution for the backscatteredfield appliedto a and 300 Hz and two bottomedarrays with aperturesup to 250 m were two-dimensionalDonelan water wavespectrum. Normal modemodel employedallowing source-receiver distances of 6-15 km undera variety predictionsusing the calculatedscattering strengths agreed with the up- of seaconditions and anglesof pathswith respectto the seas.High- and down-shiftedBragg energymeasurements in both level and azi- resolutionadaptive beamforming techniques were used to suppressgrat- muthaldependence. [Work supportedby SPAWAR PMW 192.] ing lobesand campensatefor array distortionsfrom linear. Directional beam spectraof the signalswere observedillustrating dependences on wind speedand directionwith respectto the signalpath. The resultsare 3:15 interpretedin terms of Bragg scatterfrom the surfacewave. !pUW9. Measurements of bi-statie scattering coefficients with frequency dispersive source arrays. Newell O. Booth (NCCOSC, RDT&E DIV, Code 541, San Diego, CA, 92152-6435)and Shelby 2:15 F. Sullivan,Jr. (LockheedAeronaut. Systems Co., San Diego, CA 92152) IpUW6. Comparison of UMPE/PEREV bistatic reverberation predictions with observationsin the ARSRP Natural Lab. Kevin B. A method of measuringhi-static scattering coefficients with fre- Smith (Marine Phys. Lab., Scripps Inst. of Oceanogr., Mail Code quencydispersive source (FDS) arraysis describedand illustratedwith 0704, La Jolla, CA 92093-0704), FrederickD. Tappert (University of experimentaldata. FDS array pingsform a set of narrow beamsat Miami, Miami, FL), and William S. Hodgkiss (ScrippsInst. of differentfrequencies. Signals from vertical FDS arrays are scattered Oceanogr.,La Jolla, CA) from boundaries and received on a bi-static receiver. Resolution of the scatteringarea is achievedfrom the intersectionof the time of arrival During the summerof 1993acaustic experiment sponsored by the ellipseand the conicalbeam. FDS arraysdesign principles are summa- ONR AcousticReverberation Special Research Program, bistatic bot- rized and efficientmethods of analyzingthe data usingreverberation tom reverberation measurements were made within the ARSRP Natu- models are described. ral Laboratorynear the mid-Atlanticridge. Employing a versionof the Universityof Miami ParabolicEquation (UMPE) model[MPL Teeh. 3:30 Memo, 432 (1993)] incorporatingTappert's PE Reverberation (PEREV) model, calculations of monoatatic and bistatic reverberation IpUWIO, Elastic wave scattering by an elliotieal inclusion in a within the Natural Laboratory have been made. The UMPE/PEREV fluid-saturated porous medium. Boris Gurevich, Ada P. model predictsa strongcorrelation between areas of high reverberation Sadovnichaja,Sergei L. Lopatnikov (VNII Geosystem, Moscow, and high bottom ensonifieation.Furthermore, the wave scattering Russia),and SergeiA. Shapiro (GeophysicalInstitute, University of strength predicted by the PEREV model is shown to depend on the Karlsruhe,Hertzstr. 16, 76187 Karlsruhe,Germany} bottom roughnessspectrum evaluated at the Bragg wave number The problemof the scatteringof an elasticwave by a small (com- 2kosin(&/2) where &sis the azimuthal scatteringangle. Due to the paredto the wavelengthof the fastcompressional wave) ellipticalpo- typical power-lawform of the roughnessspectrum, this suggeststhat rousinclusion placed in anotherfluid-saturated porous medium is stud- the wave scatteringstrength is enhancedin the directionof forward led usingthe Born approximation.The mechanicalbehavior of both scatter.These predictions will be comparedto the observationsand the hostand inclusion materials is described by thelow-frequency version of validity of hypotheseswill be addressed.[Work supportedby ONR, Biot'stheory. Explicit formulas for the amplitudesof the scatterednor- Code 1125OA.] mal compressionaland shearwaves and of Biot'sslow compressional

1766 J. Acoust.Soc. Am., VoL 94, No. 3, Pt. 2, Sept. 1993 126th Meeting:Acoustical Society of America 1766 wave are obtained.The effectivenessof Biot's slow wave generation operatorexpansion surface scattering methods will becompared to each dependsessentially on the ratio of the wavelengthof the slowcompres- otherover a varietyof canonicaland "realistic"surfaces. The strengths sionalwave to the inhomogeneitysize. For large valuesof this ratio the and weaknessesof each model for this task will be mentioned.Up to resultsagree with the earlier low-frequencyresults [J. G. Berryman,J. third-order implementationsof thesemethods will be used. Math. Phys.26, 1408-1419( 1985)] derivedfor a sphericalinclusion. In the oppositecase new resultsare obtained.They are usedto estimatethe effectivevelocity and attenuationof the normalcompressional wave in 4:00 a porousmedium containing randomly distributed inclusions. The fre- quencydependence of the attenuationis consistentwith the resultsfor lpUW12. The impulse responseof rough two-dimensionalsurfaces. randomlylayered porous materials. Richard S. Keiffer (NRL-SSC, Code 7181, StennisSpace Center, MS 3952%5004)and J.C. Novarini (PSI, Long Beach,MS 39560)

3:45 Previously, a model for the impulse responseof rough two- dimensional(2-D) surfaces,based on an extensionof the wedgeassem- lpUWII. Higher-order perturbation theory versus the scattering operator expansion method for 3-1) surface scattering. $ohn blagemethod, has been described (R. S. Keifferet al., Proceedingsof the SecondIMACS Symposiumon ComputationalAcoustics, Vol. 1, p. DubberIcy (NRL Code7181, StennisSpace Center, MS 39529-5004), 67), In the time that has elapsedsince this fully 3-D scatteringmodel's Jorge Novarini (Planning Systems,Inc., Bay St. Louis, MS), and Richard Keiffer (NRL, StennisSpace Center, MS 39529-5004) originaldevelopment, the validity of the WA model,which was ques- tionablefor smooth,unwedge-like surfaces has clearly beenestablished To this point little work available in the literature has examined for 2-D surfacesJR. S. Keiffer,J. Acoust.Soc. Am. (to be published)]. whether three-dimensionalscattering events can be successfullymod- More recently, the extensionof the WA method that allows for the eled by a two-dimensionalstimulation. This has mainly been causedby applicationof the techniqueto fully 2-D surfaceshas been rigorously a lack of sufficientcomputational and modelingpower in the past. A testedin a numericalstudy involvingscattering from thin disks (R. S. contributingreason to the low interestin the validity of this assumption Keiffer et al., submittedto J. Acoust. Soc. Am.). With the validity of is that thereseems to be no compellingreason why the two-dimensional the WA methodless in question,and with the increasingavailability of assumptionwould fail to correctlyapproximate the three-dimensional benchmarkquality solutions(albeit in the frequencydomain) for the situation.However, in the interestof completeness,the ramificationsof fully 3-D problem,it seemsappropriate at this time to reviewthe 3-D this assumptionmust be explored.Here two modelsare usedto provide wedge assemblagescattering program (WASP 3D) and to begin a a preliminarylook at this issue.Perturbation theory and the scattering benchmarkingexercise. [This work hasbeen supported by ONR.]

MONDAY EVENING, 4 OCTOBER 1993 GRAND BALLROOM D/E, 7:00 TO 9:00 P.M.

Session 1cid

Tutorial on Speech Perception

Judy R. Dubno, Chair Departmentof Otolaryngologyand CommunicativeSciences, Medical Universityof SouthCarolina, 171 AshleyAvenue, Charleston, South Carolina29425

Chalr's Introduction--7:00

Invited Paper

7:05

lelDl. Speechperception. Patricia K. Kuhl (Dept. of Speechand Hear. Sci.and Virginia Merrill BloedelHear. Res.Ctr., Univ. of Washington,Seattle, WA 98195) In this tutorial reviewnew conceptsand experimentalresults on speechperception, particularly its development,will be described.First, an overviewis providedof the resultsof classicalexperiments investigating speech preception in its "initialstate." Next, new resultsdemonstrating the effectsof languageexperience on speechpreception will be described,showing that the preceptionof speechis altered by exposure to languagein thefirst 6 monthsof life.Finally, preception of auditory-visualillusions in speechpreception will bedescribed, including a 90-sdemonstration experiment that allows audience members to experiencethe effect.Auditory-visual effects are discussedwithin the contextof speechperception-production links which have their inception in early infancy.A new theoryof the developmentof speechperception that incorporatesthese results will be presented.

1767 d. Acoust.Soc. Am.,VoL 94, No. 3, Pt. 2, Sept. 1993 126thMeeting: Acoustical Society of America 1767 TUESDAY MORNING, 5 OCTOBER 1993 LOWER LEVEL PLAZA, 10:00 A.M. TO 5:00 P.M.

EQUIPMENT EXHIBIT

See pagesxxxi and xxxii for the list of exhibitors.

TUESDAY MORNING, 5 OCTOBER 1993 TERRACE ROOM, 8:00 A.M. TO 12:00 NOON

Session 2aAO

Acoustical :Acoustical Determination of Polar Ocean Processes

SubramaniamD. Rajan, Cochair Departmentof •4ppliedOcean Physics and Engineering,Woods Hole OceanographicInstitution, Woods Hole, Massachusetts 02543

James H. Miller, Cochair Departmentof Electricaland ComputerEngineering, Naoal Postgraduate School, Monterey, California 93943

Chair's Introduetion-•8:00

Invited Papers

8.'O5

2aAOl. The fine scale oceanographyof the Arctic Oeeam Doppler -constie studies. Robert Pinkel and Mark Merrifield (Marine Phys.Lab., ScrippsInst. of Oceanogr.,La Jolla,CA 92093)

Focusis on fine-scalestudies of the upperArctic Oceanusing a varietyof Dopplersonars constructed at the Marine Physical Laboratory.From twoSpring experiments in the BeaufortSea (AIWEX, 1985;LEADEX, 1992),considerable insight has been gainedinto the climatologyof the internalwave field. The mostenergetic constituents of the wavefield, near inertialcur•nts, have very differentamplitudes and scalesthan at lower latitudes.The generationof thesewaves below the ice and lead-covered surfaceis consideredas a possiblefactor for their uniquecharacteristics in the Arctic. In orderto map the currentfield below an Arctic lead, a sector-scanDoppler sonarhas beendeveloped. Using beamformingtechniques, the sonarresolves acoustic back- scatterand speedalong 28 contiguousbeams with an angularresolution of 1.5'. The sonarwas deployedat two leads duringthe LEADEX experiment.Observations were obtained from a 45' verticalfan directednormal to the leadaxis. In these leads,convection associated with atmosphericcooling did not modify stronglythe backgroundvelocity field. However,a clear increasein acousticbackscatter was detected just belowthe base of the mixedlayer, possibly associated with convectiveprocesses.

2aAO2. Tomographicmeasurements of frontal variability in the BarentsSea. Ching-SangChiu (Dept. of Occanogr.,Code OC/Ci, Naval PostgraduateSchool, Monterey, CA 93943), JamesH. Miller (Naval PostgraduateSchool, Monterey, CA 93943), and JamesF. Lynch (Woods Hole Oceanogr.Inst., Woods Hole, MA 02543)

In August 1992a coastalocean tomography experiment was conductedin the BarentsSea over the steepnorthwestern slope of the Bear Island Trough, about 100 km east of Bear Island. The objectiveof the experimentwas to map and study the oscillationsof the BarentsSea Polar Front usingacoustic tomography coupled with traditionalhydrographic techniques. Because mesoscaleocean variability has shorterspatial and temporalscales in a coastalenvironment, a verticalreceiving array and frequentlytransmitting tomography sound sources were used to achievean enhancedsystem resolution appropriate for coastal monitoring.The verticalarray data were processed using plane-wave beamforming to separateray arrivalsin bothtime and angle. In addition,modal arrivals were separated using broadband modal beamforming techniques. The processedtravel time data were then "inverted"using a hybrid ray-modeinverse technique to producea time seriesof mapsof the polar front. In this presen- tation,the hybridray-mode inverse method and the frontalvariability as imagedby thisshallow-water tomography system are discussed.[Work supportedby ONR 1125ALL]

1768 J. Acoust.Soc. Am., Vol. 94, No. 3, Pt. 2, Sept. 1993 126th Meeting:Acoustical Society of America 1768 8:55

2sAC3. Observationsof acoustic scattering associatedwith ocean microstructurein the Arctic, Albert J. Plueddcmann (WoodsHole Oceanogr.Inst., WoodsHole, MA 02543), LauriePadman (OregonState Univ., Corvallis,OR), Timothy P. Stanton (Naval PostgraduateSchool, Monterey, CA), JeffreyT. Sherman,and Robert Pinkel (ScrippsInst. of Oceanogr., La Jolla, CA)

Observationsfrom an Arctic ice campon the Northwestflank of the Yermak Plateauindicate that undersome conditions oceanmicrostructure may be detectablewith "standard"acoustic instrumentation (i.e., acousticDoppler current profilers) of moderatelyhigh frequency(150-300 kHz). The data set, collectedduring the CooperativeEastern Arctic Experiment (CEAREX), includessimultaneous observations of kineticenergy dissipation rate, temperature dissipation rate, and acoustic backscatterfrom both 160-and 300-kHzDoppler profilers. The turbulencelevels observed during CEAREX wereparticularly strong(e > 10-? W kg-•) andoccurred in well-definedpatches. Patches in themixed layer were not associated with backscat- teredintensity anomalies. However, intensity anomalies of 2 to 6 dB werefound to be coincidentin time and spacewith the patchesof strongturbulence in the .The acousticintensity anomalies were intermittent, presumably because they weredetectable only above a thresholdthat representedthe backgroundparticulate scattering level. Theoretical predictions of the acousticintensity level based on themicrostructure measurements are usedto supportthe hypothesis that the enhanced scattering levelsare due to temperaturemicrostructure rather than variationsin particulatescattering.

9:20

2sAC4. Physicaloceanographic and acousticalresults from the 1988-89Greenland Sea tomographyex•riment. JamesF. Lynch (WoodsHole Oceanogr. Inst., Woods Hole, MA 02543}, PeterF. Worcester(Scripps Inst. ofOceanogr., La Jolla,CA 92093), RichardPawlowicz (WHOI), WernerMorawitz, Philip J. Sutton (SIO),and GuoliangJin(WHOI) Analysesof theacoustical tomography data taken in theGreenland Sea in 1988-1989,when combined with inputs from other environmentalmeasurements made in theregion, have yielded a numberof insightsinto both the physical oceanographic and acousticalproperties of thatpolar sea. The formation of GreenlandSea deep water (GSDW), which is of importanceto theglobal heatengine and climate studies, was imaged tomographically, allowing us to makesignificant new statements about the mech- anisms,rates, and amounts of GSDW formation.Studies of the latearriving acoustic energy have allowed both detailed studies of theevolution of thesurface mixed layer as well as a novelacoustical study of thetemporal dispersion of acousticnormal modes by that layerin the marginalice zone.Rough surface scattering processes in ice and openwater conditions, as well as ambient noise,have also been studied using the tomographydata set.

9:45-10:00 Break

ContributedPapers

10:00

10:15 2aAOS. Identificationand arrival time estimationof bandpassmodes and rays for acoustictomography in the Barents Sea usinga vertical 2aAO6. Modal inversionfor bottom sound-speedprofile in shallow array. James H. Miller, Ching-SangChiu (Code EC/Mr, Naval Arctic watersusing broadband signals. T. C. Yang (Naval Res.Lab., PostgraduateSchool, Monterey, CA 93943), James F. Lynch Washington,DC 20375) and T. Yates (Vector Res. Co., Rockville, (Woods Hole Oceanogr.Inst., Woods Hole, MA 02543), Philip MD 20852) McLaughlin,Christopher W. Miller (Naval PostgraduateSchool, Monterey, CA 93943), Keith Von Der Heydt, and John Kemp Acousticinversion of geoacousticproperties in the oceanbottom has (Woods Hole Oceanogr.Inst., WoodsHole, MA 02543) beeninvestigated recently using matched-field processing. In the shal- low Arctic waters,the acousticsignal may still be dominatedby water- borne modes.As a consequence,the matched-fieldcorrelation may not In the 1992Barents Sea Polar Front Experiment,bandpass acoustic be very sensitiveto bottom sound-speedvariation. It is found that in a tomographysignals centered at 224 Hz were receivedwith very high water depth of approximately 600 m the matched-fieldcorrelation re- SNR on a 16-elementvertical hydrophone array at a rangeof 35 km mains very high (>0.95) even with a mismatchof 50 m/s in bottom from the source.The depthof the oceanvaried from 120 m at the source sound-speedprofile. To improvethe sensitivityto bottom mismatch,we to 280 m at the verticalarray. A critical part of travel time tomography includeonly the high-ordermodes in the matched-field/modecorrela- is the measurementof the arrival time of individual modesand rays. tion. This methodis investigatedusing a simulatedbroadband signal Identifyingand trackingthese mode and rayscan be extremelydifficult and also using SUS data receivedon a vertical array. The sourceis usinga singlehydrophone in coastalwaters due to signalinterference. A localizedusing broadband matched-field/mode processing. Short-range vertical array has the potential to solve these problems.An efficient data are consideredto maximizebottom interacting signals. signalprocessing scheme is described,written in MATLAB, that simul- taneously( 1) beamformsfor the bandpassmodes or rays, (2} compen- satesfor clockdrift, samplingskew, and array tilt, and (3) compresses the maximal-length,phase-encoded signal. Data are presentedthat 10:30 showthat the beamformingalong with acousticmodeling provides idcn- 2sAC7. Broadband geoacoustieinversion in shallow Arctic water. tiffcation of the arrivals with a high degree of confidence.Errors in John W. Wolf (Naval Res. Lab., Washington,DC 20375) measuringthe arrival times are estimatedto range from 2 ms for low modesto 10 ms for high angle rays making the arrivals useful for A broadbandtechnique used successfully to localizeacoustic sources inversions.[Work supportedby ONR, Code 1125AR.] and determinewater depth and array positionat a deepPacific Ocean

1769 J. Acoust.Soc. Am., Vol. 94, No. 3, Pt. 2, Sept. 1993 126th Meeting:Acoustical Society of America 1769 site [P. C. Mignerey,Oceans '90 Proc., 121-124]is usedto determine acousticmonitoring of Arcticclimate change. The ice cover was repre- geoacousticparameters at a shallowwater site in the Arctic. The tech- sentedby a roughelastic layer with the roughnessstatistically deter- niqueminimizes differences between calculated impulse response times minedby its spatialspectrum and correlation between the upperand and pulsearrival times measuredon a verticalarray. Initially the lower ice surfaces.Horizontal change of the ice statisticsalong the method is used tø localize the source (SUS) and determine bottom supposedpaths was approximated by a stepfunction in accordancewith depthand array orientation.The methodis then appliedto pulsearriv- existingdata. The bottomrelief and horizontal variation of thetypical als that penetratethe upper sedimentarylayers of the shallowbottom. soundspeed profile were approximatedby segment-linearfunctions. In The inversionprovides compressional speed profiles and sedimentlayer the ice modelingparticular attention has been given to the influenceof thicknessesof the bottom near the array site. Differencesbetween cal- the icecracks on low-frequencypropagation loss. This canbe regarded culatedarrival timesand data showa significantdecrease, i.e., improve- asa shearwave attenuation in the brokenice plate which differs strongly ment, when usingthe geoacousticprofile as determinedby the inversion from shearwave absorptionin normal ice and mainly dependson a technique.Broadband matched-field processing is used to demonstrate meansize of the icefields. Calculated acoustic propagation loss over the inversioneffects on processorperformance. The resultsdemonstrate the trans-Arcticpaths differ from the empiricalto experimentaldata after a broadbandmethod to be usefulfor geoacoustiesurveys of shallowwater 1000-kmdistance, with the calculatedloss significantly less than the environments. empiricalprediction. This is causedby a relativeincrease of the deep- watermode contribution to the total soundfield at suchlong distances.

10:45 11:00-11:15 Break

2aAOS. Numerical modeling of long-rangelow-frequency propagation in irregular Arctic waveguide. A. N. Gavrilov, F. I. Kryazhcv, and 11:15-12:00 V. M. Kudryashov (N. N. AndrcycvAcoust. Inst. and OceanAcoust. & Inform. Ltd., 38 Vavilov St., Moscow, 1179542 Russia) PANEL DISCUSSION: An improvedmodel of the Arctic ice coverand the modecoupling Panel Moderators.'Subramaniam Rajan and JamesH. Miller approachhave been usedfor numericalcalculations of low-frexlucncy Panel Members.'I. Dyer, D. M. Farmer, M. J. Buckingham,J. R. soundpropagation over the irregular trans-Arcticpaths proposedfor Chamuel,R. Pinkel, A. J. Plueddemann,J. F. Lynch

TUESDAY MORNING, 5 OCTOBER 1993 DENVER ROOM, 8:30 TO 11:15 A.M.

Session 2aNS

Noise and Architectural Acoustics:Meeting Room Design: Acousticsor Noise?

JosephPope, Cochair PopeEngineering Company, P.O. Box 236, NewtonCentre, Massachusetts 02169

Ewart A. Wetherill, Cochair PaolettiAssociates, 40 GoldStreet, San Francisco,California 94133

Invited Papers

8:30

2aNSI. Soundin the meetingroom--A listener'sperspective. J. Pope (Pope Eng. Co., P.O. Box 236, Newton Centre, MA 02159)

Whilecareful attention is givento the visualappearance of mostmeeting spaces, the auralappearance often is neglected. Meetingrooms serve a multiplicityof functionsin a varietyof configurations.Typical of roomsat AcousticalSociety meetings, for example,is a lecture-stylesetup with a presenterat thefront of theroom addressing an audienceof 30-300listeners. A good roomwill facilitatethe communication of the presenter's message. The listener perceives, comfortably, only what the presenter wantsheard. In practice,a numberof acousticaldefects and distractions may exist. Problem areas include air-handling (HVAC) noise,sound transmission from adjacent spaces, inappropriate reverberation, noise from audio-visual presentation equipment, and audience-generatednoise. In additionto bad luck,the causesappear to includedesign, construction, maintenance, meeting planning,and facility staff issues. The useof a soundreinforcement system can mitigate some problems, while introducing new ones.The intent of this paper is to raise questionsfor discussion,and to provide an introductionto the session.

8:55

2aNS2. Meeting room design--An architect'sperspective. Curtis Worth Fentress(C. W. FentressJ. H. Bradburn and Associates,421 Broadway,Denver, CO 80203)

C. W. FentressJ. H. Bradburnand Associates was the lead designer for theColorado Convention Center, Jefferson County CourtBuilding, and for two newairport passenger terminals in Denverand Seoul. From the architect'sperspective, there are manyconsiderations in the design of meetingspaces. The author, Principal in Chargeof Design,will sharehis insight into what clientswant in design,and what clientsthink is importantto their customers.Acoustics and noiseissues are discussedin the context of the overall designproject.

1770 J. Acoust.Soc. Am., Vol. 94, No. 3, Pt. 2, Sept. 1993 126thMeeting: Acoustical Society of America 1770 9:20

2aNS3. A hotel perspectiveon meetingroom sound.Irv Ash (Carlson HospitalityGroup, Inc., 3333 QuebecSt., Ste. 114, Denver, CO 80207)

Meeting plannersbase their decisionto stay at a particular hotel, or use a hotel meetingspace, on expectationsinfluenced througha travelagent, an advertisement,word of mouth,past experience, or any numberof otherways. Regardless of motivation, serviceand comfortare the primary factorsin the decisionmaking. Comfort, like service,is a combinationof techniquesand ingredients.Discomfort is dueto a distortionof thesetechniques and ingredients.In the hospitalityindustry, discomfort can often be avoidedby gettingto know the meetingplanner, the needsof the group,and their expectations.Because hotels are generally noisyplaces, in orderto ensureguest comfort it is advantageouswhen refurbishing or buildinga hotelto work with a designer who is expertin acousticaltreatment.

9:45

2aNS4. Acoustical design of meeting rooms---A moving target. Ewart A. Wetherill (Paoletti Associates,40 Gold St., San Francisco, CA 94133)

The term meetingroom encompasses a broad range of facilities,from small,single-purpose conference rooms to very large conventionspaces that are capableof beingsubdivided and of accommodatingsimultaneous exhibits, banquets, athletics, and performingarts events.Common to all of theseuses are the requirementsfor controlof intrudingnoise and reverberation, optimizingspeech intelligibility and overall sound quality, and use of sophisticatedaudio visual and teleconference systems. These requirementspresent opportunities for innovativedesigns in whichacoustical flexibility can optimize usability for manydiverse functions.Difficulties to be resolvedinclude constraints imposed by competingdesign requirements, conditions recently mandated by Americanswith DisabilitiesAct (ADA) statutes,severely restricted budgets, and a generallack of understandingof acoustics issueson the part of clientsand builders. This paperreviews typical design issues, with examplesfrom recentprojects and with particularemphasis on the importanceof familiarity with the many acousticalpitfalls inherent in the designand construction process.

10:10

2aNSS. Audio-visualequipment noise in the meetingroom--An uninvitedparticipant. Martin Alexander (Bruel & Kjaer Instruments,Inc., 63 PassaicAve., Summit, NJ 07901)

Evenmeeting spaces that have been designed to haveexcellent acoustics and low background noise can exhibit noise problems whenaudio-visual equipment is introducedinto the room.Several common A-V equipmenttypes were evaluated with the goal of assessingsound power, tonal content, and directivity. Results of the measurements,and predictedNC and speechinterference levelsare presented.Concepts for designof quietequipment are discussed.

ContributedPaper

10:35 nonparametricstatistical analysis of the data was completedutilizing the Friedman two-way analysisof variance by ranks. The data were 2aNS6. An assessmentof automotive sound quality. Kathleen K. analyzedoverall as a function of vehicle and as a function of demo- Hodgdon(Appl. Res. Lab., StateUniv., P.O. Box 30, StateCollege, graphicsubgroups of the subjects.A retestof 20 subjectswas adminis- PA 16804) teredapproximately I monthafter initial testingto assessthe reliability The intent of this researchwas to defineand validatea statistically of the procedure.[This researchwas sponsoredby AdvancedPower- soundsubjective presentation procedure while gatheringadditional in- train Engineering,Ford Motor Company.] formationon individualpreferences for soundquality in the passenger compartmentof a six-cylindercar. Samplesof noisespectra in the pas- sengercompartments of four six-cylindervehicles were recorded in both 10:50-11:15 steadyand acceleratingmodes of operation.These noisespectra were then presentedin a multiple-comparisonlistening task to 40 individuals for subjectiveevaluation and rankingfrom most to leastpreferred. A PANEL DISCUSSION

1771 J. Acoust. Sec. Am., Vol. 94, No. 3, Pt. 2, Sept. 1993 126th Meeting: AcousticalSociety of America 1771 TUESDAY MORNING, 5 OCTOBER 1993 SILVER ROOM, 8:30 A.M. TO 12:00 NOON

Session 2aPAa

Physical Acoustics:Thermoacoustics

W. Patrick Arnott, Chair AtmosphericSciences Center, Desert Research Institute, P.O. Box 60220, Reno, Nevada 89506

ContributedPapers

8:30 9:15

2aPAal. Optimal heat-driven thermoacousticrefrigeration: The beer 2aPAa4. Thermodynamic performance of a high-power coolerrevisited. W. Patrick Arnott and Authony A. Atchley (Atmos. thermoacousficrefrigerator. David K. Perkins, D. Felipe Gaitan, Sci. Ctr., Desert Res. Inst., P.O. Box 60220, Reno, NV 89506 and Richard Russell, Ashok Gopinath, L. Todd Morris, James A. PhysicsDept., Naval PostgraduateSchool, Monterey, CA 93943) Mayfield, and Steven L. Garrett (Phys. Dept. and SpaceSystems Academic Group-Code Sp/Pk, Naval PostgraduateSchool, Monterey, The goals of this researchare to design and build an optimally CA 93943) efficientheat-driven thermoacoustic refrigerator to cool a given heat load to a desiredtemperature. The systemuses heat to drive a thermo- The coolingcapacity of a high-powerthermoacoustic refrigerator acousticprime moverthat producessound for a thermoacousticrefrig- that usesresonant high-amplitude sound in inert gasesto pump heat erator (as originallyinvestigated by JohnWheatIcy in a devicehe called will be measuredand discussed. The thermoacousticengine under study a beer cooleron accountof the temperaturesand heat loadshe was utilizestwo thermoacousticdrivers each capable of delivering60 W of strivingto obtain). Here, the firststep, numerical design, is described.A acousticpower at 325 Hz. The engineis designedto deliver205 W (700 givensystem configuration is analyzedusing Runge-Kutta integration BTUfh) of usefulcooling capacity at 4 øC(refrigerator mode) and 117 of threecoupled DE's for ambienttemperature, acoustic pressure, and W (400 BTU/h) at -22 øC (freezemode). The engineincludes two specificacoustic impedance (SAI) in the prime moverand refrigerator "stacks"with heat exchangersat eachend. Using differentialthermo- and usingpressure plus SAI transitionequations elsewhere. Complex piles,the temperaturedifference across the inlet and outletof eachof the eigenfrequencyanalysis is usedto obtainstarting values for a root find- four heatexchangers is combinedwith the fluid massflow rate to quan- ing routinefor the systemsopening acoustic pressure, hot end temper- tify heat flow. The determinationof the acousticpower delivered to the ature, heat load, and frequency.Optimization is usedto find a system resonator,combined with the heat flows,forms a completeset of ther- configuration that maximizes overall efficiency. These calculations modynamicmeasurements which permits accurate determination of the shouldshed new insightinto optimal heat exchangerlengths. Progress thermoacousticcoefficient-of-performance. These measurements allow on meetingthese goals is reported.The basicset of equationsused in the optimizationof fluid flow rates.[Work supportedby NASA--Life Sci- Runge-Kutta integrationhave intriguing forms and are discussed.Em- ence Division, the NPS Direct Funded ResearchProgram and the phasisis placedon investigationof the couplingbetween prime mover Rolex Award for Enterprise.] and refrigeratoroperation. [Work supportedby ONR.]

9:30 8:45 2aPAa$. Effective heat transfer between a thermoacoustic heat 2aPAa2. Modular thermoacousticrefrigerator. Steven R. Murrell exchanger and stack. Thomas J. Hofier (Phys. Dept., Naval and GeorgeMozurkewich (Ford Motor Co. Res. Lab., Maildrop 3028 PostgraduateSchool, Monterey, CA 93943) SRL, P. O. Box 2053, Dearborn, MI 48121-2053) Typically,hot and coldcopper fin heatexchangers couple heat into A thermoacousticrefrigerator was built to explorescaling to large andout of thestack. Effective heat transfer means that large amounts of heat flux. The refrigeratorwas constructedaccording to a modular heat are carriedacross the stackinterface with a small temperature designso that variousstack, heat exchanger,and resonatorsections are difference. Effective heat transfer is also efficient if thermoviscous losses easilyinterchangeable. The resonatoris driven by a commercial10-in. in the heat exchangerare minimized.This is particularlydifficult to woofer.Initial tests,using pure helium gas as the workingfluid and steel achievein engineshaving high-power density and largegas displace- honeycomb(0.8-ram cell) for the stack,pumped 60 W of heat against mentamplitudes. A simplemodel for heatexchanger effectiveness and a 10øC temperature gradient. Measurements of heatflux and efficiency its relationshipto fin lengthand spacingis discussed.Heat exchanger will be reportedas functionsof stack structure (e.g., pore size and fins that are shorterthan the peak gas particledisplacement can be shape) and will be comparedwith theoreticalpredictions. effectiveif the fin spacingis sufficientlysmall.

2aPAa3. Performance of a thermoacoustic refrigerator with an 2aPAa6. Experimental heat exchanger performance in a improvedstack geometry. ThomasJ. Hofier and Jay A. Adeff (Phys. thermoacousticprime mover. Nelson C. Castro, Thomas J. Hofier, Dept., Naval PostgraduateSchool, Monterey, CA 93943) Anthony A. Atchley, and David L. Gardner (Phys. Dept., Naval PostgraduateSchool, Monterey, CA 93943) The original Hofier thermoacousticrefrigerator is improvedby meansof a two-segmentstack. Each segmentof the stackcan have a The effectiveness of heat transfer between the thermoacoustic stack differentlayer separation that is approximatelybest for its localacoustic anda typicalcopper fin heatexchanger isdetermined by the detailed gas environmentand heat load. A few differentcombinations of stackseg- motion and thermal ,and the fin geometry.This effectiveness ments were testedexperimentally. The best data indicatedan increasein dependsstrongly on acousticamplitude and heat load, as doesthe abil- temperaturespan from 102 to 118øC, and an increasein COP relativeto ity of the copperto conductthe heat. Theseand other nonlineareffects Carnot of about40%, comparedto the bestsingle-stack element. contributeto limitingthe amplitude of a primemover. A modularprime

1772 J. Acoust.Soc. Am., Vol. 94, No.3, Pt.2, Sept.1993 126thMeeting: Acoustical Society of America 1772 moverexperiment has been built so that the limitingamplitude can be changer,and a coldend. The temperatureof the hot heatexchanger was measuredwith a varietyof heatexchanger geometries, with the goalof maintainednear room temperature.The temperatureof the cold cod findingthe bestgeometry. The liquid nitrogentemperature experiment was held closeto liquid nitrogentemperature ( -77 K). Measurements usesa headergas, such as neon,at a low pressurein orderto minimize wcrc made for frequenciesranging from 300 to 1200 Hz, and for dif- the heat load, and the temperaturedefects associated with coppercon- ferentcold end impedances.There is goodagreement between the mea- duction,while allowinglarge Mach numbersand gasparticle displace- suredand predictedresults. [This work wassupported by the Officeof ments.In preliminarymeasurements, peak pressure amplitudes are in Naval Research.] accessof 20% of the meanpressure and the peak-to-peakacoustic dis- placementsare comparableto the stack length.Such large displace- 11:00 mentstake the study of prime moversinto a poorly exploredregion. [Work supportedby the Naval ResearchLaboratory and the Officeof 2aPAa10. Dynamics of a dual-drlver acousticresonator and control Naval Research.] systemused in a thermoaconsticrefrigerator. D. Felipe Gaitan and StevenL. Garrett (Naval PostgraduateSchool, Monterey, CA 93943) 10:00 Until the developmentof the Thermoacousticlife sciencesrefriger- 2aPAa7. CFC-free refrigeration: Thermoacoustic technology-design, ator (TALSR) [S. L. Garrett et al., J. Acoust. Soc. Am. 93, 2364 construction,and evaluation. JosephPaul Salyards,II (Route 1, Box (1993)], all previousthermoacoustic refrigerators employed only a sin- 302-D, New Market, VA 22844) gle electrodynamicdriver. Due to the acousticpower requirements for TALSR, a dual-driver, half-wavelengthengine was designed.This in- Environmentalpriorities are forcingchlorofluorocarbons (CFC's) troducesadditional complications for the resonancefrequency control out of the marketplacethereby creating a new demandfor coolingtech- and trackingcircuitry since each driver constitutes a drivensimple har- nologies.The primary objectiveof this studywas to design,construct, monic oscillator and the two drivers, both of which have an associated and evaluatea CFC-freerefrigeration system. A prototypethermoa- microphoneand accelerometer,are coupledby an acousticallyresonant coustic(TAC) systemutilizing high-amplitude sound waves in an inert system.A computermodel of the three stronglyinteracting resonant gaswas developed, and severaldesigns were evaluated. The TAC system systemswill be describedalong with a seriesof experimentalmeasure- showedpotential as an alternativerefrigeration method with the opti- mentsthat exploreda varietyof operatingconditions. [Work supported mum designresulting in a 42.2'F drop in ambientair temperature. by NASA--Life SciencesDivision and the Naval PostgraduateSchool Potential applicationsexist in refrigerationand air-conditioning;the Direct FundedResearch Program.] cooling of satellite-bornesensors; and as either a heat-driven sonar source,cryogenic refrigeration unit, or electricgenerator. 11:15

10:1•-10:30 Break 2aPAall, Cooling effect introduced by acoustic streaming. Junru Wu, Andrew J. Winkler, and Timothy P. O'Neill (Dept. of Phys., Univ. of Vermont, Burlington,VT 05405) 10:30 It is believedthat a fetal exposureto focusedultrasound during the 2aPAaS. Analysis of a thermoaconsticsprime mover above onset of secondand third trimestersof pregnancyrepresents one of the worst- self-oscillation.Andr•s Larraza and Anthony A. Atchlcy (Phys. case situationsfor thermal effectsintroduced by ultrasound.This is Dept., CodePH/La, Naval PostgraduateSchool, Monterey, CA 93943) because( 1) the ultrasoundbeam may passthrough a distendedbladder Nonlineareffects that lead to amplitudesaturation in a thermoa- that is filledwith low attenuatingfluid, and (2) heatingeffects may be coustieprime mover,are described.The evolutionof the acousticam- mostpronounced near well-ossifiedbone of high attenuationcoefficient. plitude is describedby a homogeneousGinzburg equationof the form It was found in recentin vitro experimentsthat acousticstreaming in d.4/dt=o•4-[1•42. The linear term represents the contribution from the low attenuatingfluid may dramaticallyreduce the temperaturerise gen- poweroutput due to the temperaturegradient and viscousand thermal eratedby ultrasoundat the surfaceof bone if the ultrasoundpath con- losses.The coefficienta is positiveabove onset. The cubic term is a tains a 1ow-attenuating-fluid/thin-soft-tissuefoondstructure. [Work consequenceof the nonlinearinduced vorticity at the boundary layer supportedby Hewlett-PackardCo.] that originatesfrom irreversibleterms. In the approximationconsid- ered, the eoetficient/• is positiveand a steadystate resultsfrom the 11:30 balancebetween the linear growth and the nonlinear saturation.The steady-stateamplitudes are in qualitativeagreement with observations 2aPAa12. Convective heat transfer from a sphere due to acoustic madeby WheatIcy[Frontiers in PhysicalAcoustics, Varena (1986)] stremning. Ashok Gopinath (Dept. of Phys., Naval Postgraduate and Hofler et al. [seeabstract in this session].Observations made by School,Monterey, CA 93943) and Anthony F. Mills (UCLA, Los Swift [J. Acoust. Soc. Am. 92, 1551 (1992)] on the dependenceof Angeles,CA 90024-1597) acousticpressure versus heater power are alsoin qualitativeagreement Convectiveheat transferfrom a rigid spheredue to acousticstream- with the theory. [Work supportedby ONR and NPS Direct-Funding ing is discussedfor large streamingReynolds numbers. The work is Program.] motivated by a need for the thermal analysisof the experimentson containerlessmaterials processing using acoustic levitation. The acous- 10:45 tic signalsused in tbeseexperiments give risc to a strongsteady fluid motion aroundlevitoted alloy samples.The associatedconvective heat 2aPAa9. Thermoacoustie termination for a traveling wave tube. transferrates are significant enough to giverise to heating/coolingrates John N. Kordomenos (Dept. of Phys., Univ. of Mississippi, in the sampleswhich arc crucialin determiningtheir materialstructure University,MS 38677), Anthony A. ArchIcy (Naval Postgraduate and hencetheir thermophysicalproperties. The steadyheat transport School,Monterey, CA 93943), Richard Rasper,and Henry E. Bass effectduc to the streamingmotion is studiedwith the leviratedsample (Univ. of Mississippi,University, MS 38677) modeledas an isolatedsolid sphere in a pure planestanding sound field. A theoryfor thermoacousticsof travelingwaves has been developed Strongacoustic signals in the rangeof 150-170 dB and 1-2 kHz are andpresented previously by Raspetet al. [J. Aeoust.Soc. Am. 93, 2278 considered.Analytical and numerical techniquesare used to (A) (1993)]. In this paper, experimental results are compared with obtain a Nusselt number correlation for the heat tranafcr whcn the predictionsof this theory.The experimentconsisted of measuringthe surroundingfluid is a gas with Prandtl number •O(1). A simpleex- pressurereflection coefficient of a thermoacoustictermination located at perimentperformed to confirmsome of the predictionsis foundto give oneend of a 20-m-long,5-cm-i.d. tube. The terminationconsisted of a very goodagreement with the analysis.A moredetailed report of the hot heat exchanger,a 5-cm-long,square pore stack,a cold heat ex- resultsof this study may be found elsewhere[J. Heat Transfer 115,

1773 d. Acoust.Sec. Am., Vol. 94, No. 3, Pt. 2, Sept. 1993 126th Meeting:Acoustical Society of America 1773 332-341 (1993)]. [Work supportedby NSF Grant No. CTS-8918777 amplitudeacoustic standing waves. That studyfocused on the depen- and the NRC.] denceof AT on the positionof the platesin the standingwave. Signif- icant discrepanciesbetween the predictedand measuredresults were 11:45 observedat high acousticpressure amplitudes. Moreover, for a given meangas pressure, there wasa thresholdacoustic pressure amplitude 2sPAs13, Preliminary investigationof high amplitudestanding waves abovewhich irregularities appeared in the plotsof AT vs kx. Therewas with laser Doppler veloeimetry. Timothy J. Corrigan and Anthony evidencethat somevelocity-dependent effect might be the causeof the A. Atchley (Phys.Dept., Naval PostgraduateSchool, Monterey, CA 93943} discrepancies.An investigationof the acousticvelocity field in high amplitudestanding waves has beeninitiated to determinewhether there A previousstudy of thermoacousticheat transportphenomena are measurableirregularities in the velocity field that can accountfor lAtchIcyeta!., J. Acoust.Soc. Am. gg,251-263 ( 1990}]reported mea- the observedbehavior. Preliminary resultsof this investigationare re- surementsof the acousticallyinduced temperature difference A T gen- ported.[Work supportedby the Officeof Naval Research.] eratedacross short, poorly thermally conducting plates situated in high

TUESDAY MORNING, 5 OCTOBER 1993 GOLD ROOM, 8:30 A.M. TO 12:00 NOON

Session 2aPAb

Physical Acoustics:General Topics

Dale W. Fitting, Chair MaterialsReliability Division, National Institute for Standardsand Technology,Boulder, Colorado 80303

ContributedPapers

8:30 9.'00

2aPAbl. On statistical fluctuations in single scattering by an 2aPAb3. Nonscattering of sound by sound: Exact second-order ensembleof scatterers. George H. Gocdecke,Michael De Antonio transientsolutions. PeterJ. Westervelt (Dept. of Phys.,Brown Univ., (Dept. of Phys., NMSU, Las Cruces,NM 88003-0001},and Harry Providence, RI 02912} J. Auvermann (Army Res.Lab., BattlefieldEnvironment Directorate, WSMR, NM 88002-5501} The bilinear interactionof two primary wavesp• and p• generatesa scatteredwave Ps satisfying•12ps=--Os=--d(pd•2+ibtp2), where A=ip•c•)-'[2+pac•-•(d•p/dp•)co].Here,Pt=Pa+P,n was chosen in Expressionsin terms of thepresumed known scattering cross section whichpd=--V.[(4rrr) •O(t--c•-tr)] and p•=--(4•rcor)-I•(t of the objectsare derived for the ensembleaverage single scattering --c•-•r). Thiscombination of dipoleand monopole sources located at differentialcross section •v and its rms deviationAc•v due to a homo- r=0 has a far-field cardioid pattern with a null in the i direction.Also geneousensemble of At identicalobjects randomly positioned with no chosenwas p2=coU(i.r+ro)o[t--c•(•.r+ro)], a planewave origi- correctionsin an observedvolume V. For wavelength/t,it is well known natingat r=--r0• and travelingin the [ direction.G(t} and at(t} may that,if N3fi/V > > 1, the scatteringis essentiallyforward and coherent.Appar- bilinear interactionof prima•d waveswith their sources,the sources ently not so well known is the result of Aa•½/•/½depends on another wereactivated at t=0 and terminatedat O

2aPAb2. Locating two uncorrelated sound sources with two vector sound-intensityprobes. Robert Hickling (Natl. Ctr. for Phys. 9:15 Acoust., Univ. of Mississippi,University, MS 38677) and Alexander P. Morgan (GM Res_ Labs.. Warren. MI 48090-0055l 2aPAIM. The FDTD method for ultrasound pulse I•rolmgation through a two-dimensional model of the human breast. Charles W. Manry, Jr. and Shira L Broschat (School of Elec. Eng. & Cornput. The useof vector sound-intensityprobes for locatingsound sources Sci., WashingtonState Univ., Pullman, WA 99164-2752) is a relativelyundeveloped area. In a prior presentation[Hickling eta!., J. Acoust.Soc. Am. 93, 2357 (A} (1993)] it wasshown experimentally The incidenceof breastcancer is increasing.In 1961a womanhad that the directionof a singlesource in water could be detectedwithin a 1 in 20 changeof gettingbreast cancer; today it is I in 9. The earlier 4-2 de8 usinga probewith four pressuretransducers. It wasalso known a tumor is detected,the more likely the survivalof the victim. Thus it is that the effect of noise interference from another source could be re- criticalthat high-resolution breast imaging techniques be developed that movedby spectralsubtraction. In the presentpresentation, numerical are capableof detectingsmall tumors.One modality under consider- continuationmethods are usedto solvea set of nonlinearequations to ation is ultrasoundimaging. Algorithms developedfor ultrasoundim- determine the coordinatesand strength of two uncorrelated sound aging usuallyassume that scatteringof energyin the breastis weak, sourcesfrom measurementswith two vector probes. allowing simple and efficientimage formation algorithms.However,

1774 J. Acoust.Soc. Am., Vol. 94, No. 3, Pt. 2, Sept. 1993 126th Meeting:Acoustical Society of America 1774 experimentsconducted at the Universityof Pennsylvaniasuggest that 10:15-10:30 Break fat lobesnear the breast'ssurface refract ultrasoundenergy as it passes throughthe breast.This strongrefraction violates the weakscattering assumptionand calls into questionthe validityof algorithmsusing this 10:30 approximation.A higher-orderfinite-difference time-domain (FDTD) 2aPAbS. Computationaland experimentalinvestigation of time-shift algorithmhas been developed that canbe usedto modelthe effects of fat estimation for compensationof wave-front distortion in ultrasonic lobeson the propagationand scatteringof an ultrasoundpulse in the applicationsusing scatteredsignals. Ryoichi Kanda (Med. Eng. humanbreast. The simplebreast model used is two-dimensionalwith a Lab.,Toshiba Corp., Med. Eng.Ctr., 1385Shimoishigami Otawara-shi, fat structuresimilar to that of the Pennsylvaniastudy. Results support Tochigi-ken329-26, Japan), Dong-Lai Liu, and Robert C. Waag the conclusionthat refractionin the breastposes a significantchallenge (Univ. of Rochester,Rochester, NY 14627) to ultrasoundimaging. [Work supportedby NSF.] Time-shiftcompensation of wave-frontdistortion that degradesim- agesin medicalultrasound has beenstudied using computations and 9:30 measurements.In the computations,wave-front distortion was assumed to arisefrom a phasescreen placed at variousdistances from the receiv- 2aPAbS. Scattering by a layered poroelastic obstacle embeddedin a ing aperture.Intensity patterns were determinedfrom uncompensated poroelastichost. RaymondLira (Code 130B, CoastalSystems Sta., data and from data compensatedwith time-shiftestimates made in the Panama City, FL 32407-7001) aperture.In the experiments,waveforms scattered by a wire targetand A transition-matrix formulation of the field scattered by a threc- randomlydistributed particles were collectedfor a water path and for a dimensional,multilayered, poroelastic obstacle embedded in a poroelas- tissuepath. Images were reconstructed from uncompensated data, from tic host is obtainedby extendingPeterson and Str6m formulationfor datacompensated with time-shiftestimates made in the receivingaper- scalarwaves [B. Petersonand S. Str6m, J. Acoust.Soc. Am. 57, 2-13 ture, andfrom datacompensated with time-shiftestimates made after a (1975)]. An exactsolution of the vectorBlot equationsis obtained, backpropagationstep in whicha waveformsimilarity factor was maxi- obeyingall boundaryconditions prescribed on all boundariesof the mized. The results show the limitations of time-shift estimation in the layeredobstacle. By numericallyimplementing the solutionfor general aperturefor compensationof wave-frontdistortion produced by a phase poroclasticmedia, scattering with hostsand obstacles made of lossgen- screenthat is not closeto the receivingaperture. The resultsalso show eral mediais convenientlypredicted by choosingmaterial parameters in that the additionof a backpropagationstep before time-shift compen- a limitingsense. Examples are presentedto studythe scatteringdynam- sationcan improvethe characteristicsof the focus. ics of layeredspheres and sphericalshells embedded in fluid and po- roelastic hosts. 10:45

2aPAb9. Acoustic band structure in liquids and gnses--fce pattern 9:45 with sphericalballoons. M. S. Kushwahaand P. Halevi (Inst. de 2a_PAb6.Green's functionsfor wave propagationin range-dependent Fisica,Univ. Aut6nomade Puebla,Apdo. Post.J'-45, Puebla 72750, inhomogeneousmedia•Some exact analyticsolutions. Y.L. Li (US M6xico) Army ConstructionEng. Res. Lab., P.O. Box 9005, Champaign,IL The first extensiveband structurecalculations in periodicstructures 61826-9005) madeup of liquidsand gases are reported.The specificsystem studied Three exact analytic solutionsof the Helmholtz equation are ob- in the presentinvestigation is sphericalair (water) balloonsin a peri- tainedin closedform for the caseof a point sourcein range-dependent odicpattern in water (air)--the fccarrangement. Since only longitudi- inhomogeneousmedia. The solutionsare obtainedby startingwith a nal wavescan propagate, the generalwave equation is greatlysimplified. onefoldintegral representation for the solutionthat is derivedfrom the The pertinentparameters are the densitiesand the longitudinal-sound path integral.For a pointsource in suchmedia above either a softor velocities.Depending upon the fillingfraction a numberof bandgap(s) hardground, the exactanalytic solutions are alsoderived. These solu- extendingover the wholefirst Brillouin zone are found.Within these tionsare particularlyuseful for testingthe validityof approximateor bandgaps vibrations and sound propagation are prohibited. A complete numericalsolutions for caseswith a range-dependentbackground me- acousticgap or zero densityof statesshould have importantconse- dium.They alsofacilitate construction of moregeneral solutions for quencesfor therealization of noiselessenvironment and for the local- problemswith scatteringin a range-dependentbackground medium, izationof longitudinalsound waves. The precise dependence of theband throughthe useof integralequation techniques. gapson the fillingfraction is alsoinvestigated.

10:00 11:00

2aPAb7. Performanceanalysis of transient acoustic wave modeling 2aPAb10. Photonic band gaps in I•riodic elastic composites2-D usinghigher-order WKBJ asymptotiesand symbolicalmanipulation. hexagonallattices. M.S. Kushwahaand P. Halevi (Inst. de Fisiea, Martin D. Verweij (Lab. of ElectromagneticRes., Dept. of Elec.Eng., Univ. Aut6nomade Puebla,AlXlO. Post. J-45, Puebla72570, M•xico) Delft Univ. of TechnoL, P. O. Box 5031, 2600 GA Delft, The The acousticband structure of periodicelastic composites were cal- Nctberlands) culatedusing position-dependent density and elastic constant. The spe- The methodof modelingtransient acoustic waves in continuously cificsystem investigated is madeup of a periodicarray of parallelme- layeredmedia using a combinationof higher-orderWKBJ asymptotic tallic rods of circular cross section whose intersections with a representationsand the Cagniard-DeHoop method is addressed.The perpendicularplane from a hexagonallattice. The rods are embedded in coefficientsof the WKBJ asymptoticrepresentations satisfy a recurrence a backgroundmedium with differentelastic constant and density. The scheme,which is easilydealt with by applyingsymbolical manipulation. transversepolarization was considered--with displacement u(r,t) par- Moreover,an efficientuse of the Cagniard-DeHoop methodof inver- allel to the cylinders(and perpendicularto the Bloch wavevectors). sionis achieved[M.D. Verweij,J. Acoust.Soc. Am. 92, 2223-2238 The absoluteband gaps extending throughout the first Brillouinzone (1992)].The performance of this method is discussedon thebasis of werefound in the low-frequencyregime. The specificcase studied was numericalresults for a seriesof configurations.In particular it is shown Cu(AI) cylinders in the AI(Cu) background. A direct comparisonof howthe method performs if transcendentalparameter profile functions the hexagonalcase with the square-latticepattern (Kushwaha et al., arereplaced by least-square-fit polynomials. From the results it is con- precedingabstract in thissession) reveals that the widthsof theseband eludedthat the methodperforms best for low-orderpolynomial param- gapsare larger in thecase of hexagonallattices. The precisedependence eter profiles. of the gapson the fillingfraction is investigated.

1775 J. Acoust.Soc. Am., Vol. 94, No. 3, Pt. 2, Sept.1993 126thMeeting: Acoustical Society of America 1775 11:15 obtainedwhen they are dropped,where 0 is the scatteringangle. It is alsoshown that thisBorn scattering amplitude is identicallyzero in the 2aPAbI1. Coupled wave equations for numerical calculation of forwarddirection for any solenoidalflow velocityfield that goesto zero acoustical propagationand scattering by atmosphericturbulence. fasterthan r -a asr• oo.Analytic expressions and numerical results for Michael De Antonio,George H. Goedecke (Dept. of Phys.,NMSU, the first Born differential and total cross sections are obtained for a Las Cruces,NM 88003-0001), and Harry J. Auverrnann (Army Res. modellocalized turbule. The modelemploys nonuniform rotation about Lab., Battlefield Environment Directorate, WSMR, NM 88003-5501) an axis,as modulated by an axisymmetricGaussian, plus commensurate The usualapproximate acoustic wave equations [e.g., A.D. Pierce, temperaturevariation. J. Acoust.Soc. Am. 87, 2292 (1990)] weredeveloped for ambientcon- ditions (turbulence)in which the scalelength a of the spatialvariation of temperatureand flow velocityis much larger than the acoustical 11:45 wavelength•.; this is not the casein many applicationsof interest.An alternativeset of coupledacoustical wave equations, valid for any a/;•, 2aPAb13. The study of the influence of boundary layer effect upon is presented.These equations involve no approximationsexcept the the standingwave in an open resonator. Yulia J. Benson (Math. & usualneglect of the viscosityterms in the Navier-$tokesequation for Mech. Dept., St. Petersburg,State Univ., 2 Bibliotechnayap!., St. the acousticflow. For quasistaticor "frozen" turbulence,the integral Petersburg198904, Russia) formsof theseequations are presented,suitable for applicationof the A simplestmodel approach to the problemof the studyof nonlinear digitized Green's function method [O. H. Goedeckeand Scan G. processesin an open resonatoris proposedhere. It is basedon the O'Brien, Appl. Opt. 27, 2431 (1988)]. considerationof the only act of propagation--reflectionof the wavein an open-endedtube. In other words,one can studythe incomingwave 11:30 distortionduring wave propagationforward to the closedend (piston) and backward.According to the experimentaldata the processof oscil- 2aPAb12. First-order acoustical wave equations and scattering by lation in somecases is mostlydefined by thesedistortions. For example, atmosphericturbulence and turbules. George H. Goedecke,Paul M. the experimentlB. Sturtevant,J. Fluid Mech.63, pt. 1, 97-120 (1974)] Pellegrino,Michael De Antonio (Dept. of Phys.,NMSU, Las Cruces, predictsthat a shockwave shouldbe formed during the propagation NM 88003-0001), and Harry J. Auvermann (Army Res. Lab., considered.The numericalanalysis of the standardBurgers' equation WSMR, NM 88002-5501) plus the term that was derived by Blackstuck[D. T. Blackstuck,J. The first Born approximationhas often been used to predictacous- Acoust.Soc. Am. 77, 2050-2053(1985)] in orderto describean influ- ticalscattering by the quasistatictemperature fluctuations and velocities enceof the boundarylayer at the walls on plane travelingwaves allows associatedwith atmosphericturbulence. For this approximation,only one to concludethat an accountof this effectpermits one to obtain a termslinear in thesedisturbances need be retainedin the waveequation. good agreementwith the resultspredicted by Sturtevant'sexperiment. Terms in this first-orderwave equation involving spatial derivatives of Moreover such a statementcan be regardedas an inverseproblem, so the flow field haveoften been dropped. It is shownthat retainingthese that it is possibleto restore the boundary condition using the experi- terms yields a Born scatteringamplitude equal to cos(O) times that mental data.

TUESDAY MORNING, 5 OCTOBER 1993 VAIL ROOM, 8:25 A.M. TO 12:00 NOON

Session 2aPP

Psychologicaland PhysiologicalAcoustics: Potpourri

William A. Yost, Chair Parrnly Institute, Loyola Unioersity,6525 North Sheridan Road, Chicago,Illinois 60626

Chair's Introduction---8:25

Contributed Papers

8'.3O equallyto enhancedetection by as muchas 10-12 dB relativeto energy detection alone. The derivation of the new detection model will be 2aPPI. Prediction of masked detection thresholds for noise signals explainedand predictionsfrom the new modelwill be comparedwith centered in a sated noise mosker. C. Formby (Dept. of experimentally measured masked detection thresholds.The overall OtolaryngoL--HNS, JohnsHopkins Univ., P.O. Box 1737, Baltimore, agreementbetween predicted and measuredthresholds is excellent {r MD 21203), M.G. Heinz, and C. E. Luna (JohnsHopkins Univ., =0.95). [Researchsupported by NIH.] Baltimore, MD 21218}

A new detectionmodel can predictmasked detection thresholds for a rangeof signalbandwidths ( W=62-6000 Hz) and durations( T= 10 8:45 to 500 ms) for noisesignals centered at 2500 Hz in an uncorrelated 2aPP2. The effectsof level and frequencyregion on the reeoveryof 500-ms, 6000-Hz-wide masker (N0=53 dB SPL/Hz). The new model overshoot. Gary J. Oversonand Sid P. Bacon (Psychoacoust.Lab., effectivelytakes into accountrelative cues resulting from temporaland Dept. of Speechand Hear. Sci., Arizona State Univ., Tempe, AZ spectraldifferences between the signaland maskerto supplementenergy 85287-1908) detection.These relative cues are ( 1) greatestwhen the durationsand spectraof the signaland musketare most disparateand (2) eliminated The term "overshoot"refers to the findingthat the thresholdfor a when the signaland maskerare matchedtemporally and spectrally.The brief signalcan be higher when that signalis presentedshortly after relative timing and spectral shape cues combine independentlyand maskeronset than when it is delayedby a few hundred ms. Overshoot

1776 J. Acoust.Soc. Am., VoL 94, No. 3, Pt. 2, Sept.1993 126thMeeting: Acoustical Society of America 1776 canbe reduced or eliminatedby presenting a stimulus (precursor) prior Subjectswere required to detecta 1000-Hzsignal in thepresence of to maskeronset. The "recoveryof overshoot"can be examinedby vary- a maskerthat consistedof a 1000-Hz(on-frequency) component alone ing thedelay between the offset of theprecursor and the onset of the or that componentand six flanking components (500, 600,700, 1300, masker.The purposeof experimentI wasto evaluatethis recoveryat 1400,and 1500Hz). The on-frequencycomponent typically was sinu- two (maskerand precursor)levels, one relatively high and onerela- soldallyamplitude modulated at 10Hz andthe signal was presented in tivelylow. Overshoot was first measured as a functionof maskerlevel in a dip in the envelopeof the on-frequencycomponent or in threesuc- orderto choosetwo fairly disparatelevels that producednearly equiv- cessivedips. In experimentI, the flankingcomponents could lower alent amountsof overshoot.Recovery functions were then measuredat (comodulationmasking release or CMR) or elevate(across-channel thoselevels. In general,there was little differencein the recoveryat the maskingor ACM) threshold,depending upon whether they were mod- twolevels. In experiment2, theprecursor was sectioned into two bands, ulatedin phasewith theon-frequency component, or staggeredin phase. one on either sideof the 4.0-kHz signalfrequency. Recovery was mea- CMR wasobserved for bothsignal types, although it wassmaller for the suredseparately for eachband, while the other band was presented three-burstsignal. ACM wasonly observedfor the three-burstsignal. continuously.There was a tendencyfor the recoveryto dependmore Thesedifferences were primarily due to lowerthresholds in the presence uponthe bandabove the signalfrequency, suggesting that that region of the on-frequencycomponent alone for the three-burstsignal. In ex- may be mostimportant for overshoot.[Work supportedby NIDCD.] periment2, thresholdswere measured as a functionof the modulator phaseof the flankingcomponents. The on-frequencycomponent was unmodulatedor 100% amplitudemodulated (modulator phase of 0ø). 9:00 For both monoticand dichoticpresentations of the flankingcompo- 2aPP3. Effectsof amplitudemodulation on gap detectionin wideband nents,thresholds increased and thendecreased as the modulatorphase noisebursts.Karen B. Snell (Dept. of Audio1.,Rochester Inst. of of theflanking components varied together from 0 to 360'.[Work sup- TechnoL,Rochester, NY 14618) and Ajit 1anardan(Boston Univ., portedby NIDCD.] Boston, MA 02215)

Recentstudies suggest that fluctuationsin the envelopesof narrow- 9:45 bandsignals influence the detection of temporalgaps. In thisstudy, the 2aPP6. The effects of cross-spectrumenvelope correlation on effectsof amplitudemodulation on gapdetection using wideband noise- detection of a signal band: A comodulationdetection difference burstswere measured by varyingdepth of modulationand phaseangle. (CDD) experiment. Patrick W. Rappoldand John R. Carter (Dept. Gap detectionthresholds were obtained for four subjectswith normal of SpeechPathol. and Audiol., Univ. of South Alabama, 2000 hearing.The digitizednoisebursts were 6 kHz in bandwidthand 150ms UniversityCommons, Mobile, AL 36688) in duration. The level of each noiseburstwas jittered (70-75 dB SPL) and modulatedwith a 20-Hz sinusold.Gaps were placed 100 ms after Most CDD and comodulationmasking release (CMR) studiesem- stimulusonset. Gap detectionthresholds were estimated at six modu- ployonly two conditions;a correlatedcondition and an uncorrelated lation depths(0 to 100%) and at one randomand three fixedphase condition.Temporal envelopes of noisebands are identicalin the cor- angles.A continuouswhite noise (45 dB SPL) wasmixed with the relatedcondition and degreeof envelopecorrelation is the same (r signals.Thresholds were obtained in anadaptive, 2IFC procedureusing = 1.0) acrosstrials within this condition.In the uncorrelatedcondition 100trial runs.Twenty-four conditions were completed in randomorder envelopesof the noisebands arc not identical,but degreeof envelope in 2 h. Severalreplications were completed by subjects.Mean gapde- correlationfluctuates across trials within this condition.Thus, reported tectionthresholds increased with depthof modulationand variedwith thresholdsfor correlatedconditions represent the average threshold at a phaseangle. Mean gap detection thresholds were smallest (2.5-4.0 ms) singledegree of correlation,whereas reported thresholds for uncorrc- for the noiseburstswhich were least modulated (0-40%). Mean thresh- latedconditions represent the averagethreshold across various degrees oldswere largest (20 msor more) for the noiseburstsmodulated 100% of envelopecorrelation. In this studythresholds arc determinedfor at a randomphase. These results are consistentwith recentfindings signalbands centered at 2000Hz, in thepresence of cuebands centered usingnarrowband signals [B. R. Glasbergand B.C. J. Moore,Hear. at 1500Hz, at specificdegrees of temporalenvelope correlation (r= 1.0, Res. 64, 81-92 (1992)]. 0.75, 0.60, 0.50, 0.40, 0.25, 0.0, --0.25, --0.35). Thresholdsat r= 1.0 and 0.75 arc about 10 dB higherthan thresholdsat r--0.25, 0.0, and 9:15 negativedegrees of correlation.Thresholds at r=0.50 are about5 dB lessthan thresholdsat r=0.75 and above,and about 5 dB greaterthan 2aPP4. Modulation detection interference (MDI) for randomly thresholds at r=0.25 and below. Thresholds at r=0.60, 0.50, and 0.40 fluctuatingenvelopes. L. Mendoza,J. W. Hall, andJ. H. Grose (Div. are nearlyequivalent. These findings suggest that at leastthree condi- Otolaryngol./Head& Neck Surgery,Univ. North Carolina,Chapel tions(ranges of correlation)should be employedin CDD, CMR, and Hill, NC 27599-7070) other studiesinvestigating the influenceof envelopecorrelation. Modulation detectioninterference (MDI) was measuredin normal- hearinglisteners for stimuliwith randomlyfluctuating envelopes. The 10:00-10:15 Break stimuliwere generated by modulatingpure-tone carriers by de-shifted low-passnoises (cutoff= 10 Hz). The targetcarrier was 1000 Hz and the interferercarrier 2250 Hz. The targetcould be presentedeither 10:15 alone(baseline condition) or in conjunctionwith the interfererthat was 2aPW?.Effects of amplitudemodulation onprofile detection using eithergated synchronously with the targetor waspresented continu- multiple short signals. Michael A. Smith and Sid P. Bacon ously.The interferer could be unmodulated, comodulated with the tar- (Psychoacoust.Lab., Dept. of Speechand Hear. Sci., ArizonaState get,or modulatedindependently from the target. Results indicated sub- Univ., Tempe,AZ 85287-1908) stantialMDI in thepresence of the interfererboth for comodulatedand independentlymodulated envelopes. The differential gating effects will The detectionof an incrementin a targetcomponent is moredifficult becompared to thosefor sinusoidal amplitude modulations. [Work sup- whenthe surrounding,nontarget components are sinusoidallyampli- portedby theNIDCD R01-DC00418.] tudemodulated [H. Dai andD. Green,J. Acoust.Soc. Am. 90, 836-845 ( 1991)]. Thepurpose of thepresent study was to determinewhether the detrimentaleffects of amplitudemodulation (AM) on profileanalysis 9:30 couldbe eliminated by providinga relatively"static" profile during the 2aPPS. Someeffects of modulatorphase on the detectionof a signal course of AM. The task was to detect an increment in a l-kHz target in a sinusoidallyamplitude-modulated tonal complex. Michelle L. componentthat wascentered in a complexcontaining 21 logarithmi- Hicks and Sid P. Bacon (Psychoacoust.Lab., Dept. of Speechand callyspaced components ranging in frequencyfrom 200 to 5000Hz. Hear. Science,Arizona StateUniv., Tempe,AZ 85287-1908) The targetcomponent was always unmodulated whereas the nontarget

1777 J. Acoust.Soc. Am., VoL 94, No. 3, Pt. 2, Sept. 1993 126thMeeting: Acoustical Society of America 1777 componentswere either unmodulated or sinusoidallyamplitude modu- levelof 200 ml and a 1.0-kHzhigh-pass noise at 5J dB (A-weighted). lated at a rate of 10 H• The signalwas composedof multiple 20-ms The minimumbimodal angle (MBA) thresholdwas compared to that presentations,all positionedat successivepeaks, valleys, or leading of the minimum visible angle (MVA) and minimum audible angle edgesof the modulationcycle. As in previouswork with longersignals, (MAA) thresholdsand found to inoreaseperformance significantly thresholdsgenerally increased with increasingmodulation depth. An over the singlemode localizationtasks, except at 0-deg azimuththat attempt to accountfor the effectsof AM in terms of the short-term equaledthe MVA for most subjects.The implicationsof these results pedestalresulting from the modulationwas only marginallysuccessful. are discussed. [Work supportedby NIH and SigmaXi.] 11:15

10:30 2aPPII. A cross-correlation model of eommon-per'od grouping. 2aPPg. Which ear has the asynchronoussi•nl? Irwin Pollack Daniel P. W. Ellis (MIT Media Lab PerceptualCornput. Group, (Mental Health Res. Inst., Univ. of Michigan, Ann Arbor, MI EIS-36gc, Cambridge,MA 02139) 481o9-0720 ) When extractingand identifyingvowels from noisyhackgrounds, Smalldifferences in the frequencyof puretones are heard as changes the humanauditory system must identify which frequency regions "be- in loudness,either when the tonesare presentedwithin the sameear long" to the vowel (as formants), and which are extraneous.This is (monauralbeats) or when presentedto the separateears (binaural probablybased, at leastin part, on the commonpitch-period amplitude- beats).With complextones, comparable differences in fundamentalfre- modulationof all theseregions. Previous computer models of this pro- quency(asynchrony) are heardas changesin roughnessor musicality. cesshave usedautocorrelation to identify this cue within each channel With two fundamentalfrequencies presented to eachear, a wide com- of a bandpassarray JR. Meddis and M. J. Hewitt, if. Aconst.Soc. Am. bination of monaural and binaural roughnesschanges are produced. 91, 233-245 (1992)]. Autocorrelation,however, is lesseffective for sig- Under conditionswhere monaural and binauralroughness changes are nMs exhibitingrapid frequencymodulation or jitter, even thoughthese clearlydetected, the identificationof which one of the two earsis asyn- are strongcues to fusion. A model is proposedthat detectscomodula- chronous(one ear asynchronous,the other ear synchronous)is at tion synchronybetween frequency bands through a simplifiednonlinear chance.Substantial interaural differencesin intensity are required for approximationto the cross-correlationfunction. By groupingbands that the successfuluncoupling of the asynchronousear. showa steadymodulation skew, pitch-period fluctuation can be usedto reinforcegrouping rather than weakenit. The physiologicalplausibility of sucha processis alsoargued. 10:45

2aPP9. Auditory apparent motion in the horizontal and median 11-•0 planes. ThomasZ. Strybel (Dept. of Psychol.,California State Univ., 2aPPI2. Loudness growth of complex stimuli in normal-hearing Long Beach,CA 90840) listeners. Lidia W. Lee (Dept. of Commun. Disoral., Northem The rangeof stimulusdurations and interstimulusonset intervals Illinois Univ., DeKalb, IL 60115-2899) and Larry E. Humes (ISOls) that producedthe illusion of auditory apparentmotion (Indiana Univ., Bloomington,IN 47405) (AAM) were measuredwhen two sound sourceswere separatedin This paperexamined whether an excitation-patternmodel of loud- either the horizontal or median planes.Three speakerarrangements nesscould adequately describe the growthof loudnessfor complexstim- were tested,350 • and 1(• azimuth at 0 • elevation,(Y' and 180• azimuth at uli presentedto normal-hearinglisteners in quiet and in noise.The 0• elevation,and 0' and 20• elevationat if' azimuth. Subjectswere in- loudness-growthfunctions were obtainedfor three synthesizedsteady- structedto categorizetheir perceptionof the stimulussequence into one state vowels (/a,i,u/), each with two talkers (male: F0= 120 Hz; f•- of five categoriesthat were basedon the numberof sourcesheard and male: F0=200 Hz), and for several pure tones (125--4000 Hz). All whether or not motion was perceived.Subjects also indicated the rela- stimuli were presented,at random,from 2 to 90 dB SPL (in 4-dB steps) tive locationof the leadingstimulus. For each speakerarrangement, in quiet and in spectrallyshaped noise. Magnitude estimationwere used stimulus durations of 10, 25, and 50 ms and ISOIs between 2 and 70 ms to measure the loudness of each stimulus. These data are used to eval- were tested.The planein which the sourceswere locateddid not affect uate the predictionsof an excitation-patternmodel [E. Zwicker and B. the timing conditionsthat producedthe illusionof motion.AAM was Scharf,PsychoL Rev. 72, 3-26 (1965}] and a simplermodified power- heard for stimulus durations of 25 and 50 ms at ISOI values that were law model [L Humesand W. Jesteadt,L Aconst.Soc. Am. 85, 1285- roughlyequal to stimulusduration for all of the speakerarrangements 1294 (1989)}. [Work supported,in part, by NIA.] tested.However, judgments of the locationof the leadingsource were affectedby the arrangementof the speakers.Performance on this task 11:45 wasbest when the sourceswcrc separated in the horizontalplane. 2aPPI3. Word discrimination in varions multitalker noises. Tomasz

11:00 Letowski,Andrea Tornatore, Serf Clark, and BarbaraMacBeth (Dept. of Commun. Disord., Penn State Univ., 5 Moore Bldg., University 2aPPI0. Locnli,•tion performance is enhanced under bimodal Park, PA 16802) conditions of the auditory and visual spatial channels. Brian L. Costantinoand David R. Perrott (Psychoaconst.Lab., California State A large numberof differentmultitalker noises(MTNs) is usedin Univ., Los Angeles,CA 90032) researchand clinical applications.These noises differ in aooustical,se- mantic,and linguisticproperties and, thus, may have different masking A •luential localization task cornparcelthe ½lTc•tsof unimodal vcr- effectiveness.The authors compared acoustical characteristics and snsbitnodal spatial acuity in the auditoryand visualperceptual systems. maskingeffectiveness of severalMTNs recordedby the authorsand by The four subjectswere testedin a two-alternativeforced-choice, three others. Both spectral and temporal differenceshave been observed down-one up adaptive paradigmin which two 200-ms signalswere among various MTNs. When noisesof similar acousticcharacteristics presentedsequentially with a 1000-ms inter-stimulnsinterval. Tests havebeen compared, the genderof the talkersbut not the speechma- were administeredwith a 620-nmlight emittingdiode at a luminanee terial affectedmasking effectiveness of the MTN.

1778 d. Acoust.Soc. Am., Vol. 94, No.3, Pt. 2, Sept.1993 126thMeeting: Acoustical Society ot America 1778 TUESDAY MORNING, 5 OCTOBER 1993 CENTURY-SPRUCE ROOM, 8:55 A.M. TO 12:00 NOON

Session 2aSA

Structural Acoustics and Vibration: Characterization of Viscoelastic Materials I

Bruce Hartmann, Coehair Naval SurfaceWarfare Center,10901 New Hampshire•tvenue, Silver Spring, Maryland 20903

Wayne T. Reader, Cochair VectorResearch Company, Inc., 2101 JeffersonStreet, Rockville, Maryland 20852

Chair's Introduction---8:$5

Invited Papers

2aSAI. Characterizationof viscoelasticmaterials using the resonantmodes of a "free-free"bar. David A. Brown (Phys.Dept., Code PH/Br, Naval PostgraduateSchool, Monterey, CA 93943)

The techniqueof usingthe resonantmodes of a "free-free"bar to determinethe elasticproperties of the bar materialwill be described.A barcan be clcctrodynamically and selectively excited in threeindependent vibrational modes by mountingsmall coils of magnetwire on eachend of thesample. When the sampleends are placedin a magneticfield, a currentthrough one coil will inducevibrations that canbe detectedby monitoringthe cmf producedin a secondcoil. The elasticshear modulus is determined by measuringthe frequencyof the torsionalmode. The Young'smodulus is determinedfrom the frequencyof either the longitudinalor flexuralmode. The losstangent, tan 8, of the materialcan be obtainedby measuringthe quality factor of each resonance.Results from a sampleusing a transferfunction technique will be comparedwith resultsobtained using a phase-locked loop (PLL). The transferfunction technique is convenient,since the voltageacross the detectioncoil is proportionalto the velocityof the sampleand the currentdelivered to the excitationcoil is proportionalto the forcedelivered to sample.Their ratio is proportionalto the impexianceof the material.The lock-in methodis attractivebecause it offersa meansto continuously monitor the propertiesof the material.

9:30

2aSA2. Resonanceapparatus for characterizationof viscoelasticmaterials. Bruce Hartmann, Gilbert F. Lee, and John D. Lee (PolymerSci. Group, Naval SurfaceWarfare Ctr., SilverSpring, MD 20903-5640) A resonanceapparatus for the characterizationof viscoelasticmaterials will be described.Measurements have been made of modulusvalues as low as 0.1 MPa and as high as 70 GPa and lossfactors from 0.003 to 2.5. Material propertiesare determined as exact (numerical) solutionsof the wave equationwith no simplifyingassumptions. In particular,the lossfactor is not calculatedfrom the half-powerpoint and is valid for largevalues of lossfactor. By bondingthe sampleto the driver, clamping errorscommon with other instrumentsare eliminated.For any givenmeasurement temperature, the frequencyrange of the measurementsis about 1.5 decadescentered at about 1 kHz. Dependingon the samplelength and modulus,data can be obtained from 100 Hz to 25 kHz. Oncemeasurements have been made as a functionof temperature,the data are shiftedto form a master curveand fitted to an analyticalmodel. Illustrative data will bepresented for a high-lossand a low-losspolyurethane. [This work wassponsored by the IndependentResearch Program of the NavalSurface Warfare Center.]

10:00

2a•A3. Accuracyof dynamicmodulus measurements made with the dynamicmechanical thermal analyzer. R.J. Deigan and J. J. Dlubac (Code 7451, ShipAcoustics Directorate, Carderock Div., Naval SurfaceWarfare Ctr., Bethesda,MD 20084-5000) The accuratedetermination of the complexmoduli of viscoelasticmaterials is of greatimportance for the efficientdesign of manynoise control devices. It is oftenthe casethat a design,in conjunctionwith its acousticperformance requirements, leads to a narrowband of acceptabledynamic modulus for the viscoelasticmaterial. In suchcases knowledge of the accuracyand reliabilityof the measurementapparatus is essential.Dynamic complex shear modulus is measuredat CardcrockDivision Naval SurfaceWarfare Center (CDNSWC) with the Dynamic MechanicalThermal Analyzer (DMTA), manufacturedby Polymer Laboratories.An attemptto quantifythe absoluteaccuracy of the DMTA measurementhas been made through the consideration of errorsincluding the accuracyof the beamsolution used to infer the complexmodulus, compliance of the samplemounts, •neasurementnoise, temperature control, thermal stress, Poisson effects, and the implementation of time-temperature superpo- sition.With theseconfiderations, an ad hocerror analysisis implementedto quantifyabsolute error boundsexpected for DMTA measurementsof a hypotheticalmaterial. These resultsare of direct interestto the ASA Committeeon StandardsS2WG79, "Characterizationof the DynamicProperties of ViscoelastiePolymers," which has initiated round-robin testing among commit- tee participants.CDNSWC resultsfrom the DMTA testsof threeround-robin materials will be presented.

1779 d. Acoust.Soc. Am., VoL 94, No. 3, Pt. 2, Sept. 1993 126th Meeting:Acoustical Society of America 1779 10:.30

2a•A4. Dymunicmechanical properties of S2WG?9 viscoelasticpolymer samples and other compositematerials. Robert D. Collier (Dept. of Mech. Eng., Tufts Univ., Medford,MA 02115)

S2WG?9 candidatematerials for standardizationhave been measuredin accordancewith proceduresrecommended by the Working Group. The measurementshave been performed with the Tufts viscoanalyzerwith a frequencyrange up to I kHz. Resultsfor the candidatematerials include complex Young's modulus,shear elastic modulus,and associatedloss factors as a functionof frequencyand temperature.Multi4ample testingprovides statistical measures of measurementerrors and sample variations.Results are presented in formatsfor readycomparison with thoseof otherinvestigators. In addition,results of research on curedepoxy resins and selecteddental composites illustrate relationships between measured glass transition and compositematerial compositions.

11:00

2aSAS. Servohydraulicapplications for vibration damping measurement. Kirk K. Biegler (MTS SystemsCorp., 14000 TechnologyDr., Eden Prairie, MN 55344-2290) In recentyears, the rangeof performancehas been expanded for servohydraulictest systems utilized for vibrationdamping measurement.The testsnow include:(I) temperature,frequency, and amplitudeeffects on dynamiccharacteristics, (2) fatigue effectson dynamicor staticproperties, (3) resonantfrequency determination, (4) stressrelaxation after impact, (5) tearing energyanalysis, and (6) staticdeflection measurement. The performancecapabilities of servohydraulictest equipmentreadily availabletoday will be reviewed.Performance capabilities include the rangeof loadingamplitudes, rates, and frequencies and also the automationcapabilities that relateto the easeof useand versatilityof data analysiscurrently available. Some of the most recentimprovements will be highlightedto showthe extendedrange of teststhat servohydraulicscan achieve.

Contributed Papers

11:•0 11:45

2aSA6. Vlscoelasfic characterization of materials using a dynamic 2aSA7. Determination of the static moduli of viscoelasti½polymers. hardnesstester. W. Madigosky, R. Fiorito (NSWCWOD, 10901 Wayne T. Reader and David F. Sauter (Vector Res. Co., Inc., 2101 E. New Hampshire Ave., Silver Spring, MD 20903-5640), and H. JeffersonSt., Ste. 700, Rockville, MD 20852) '0befall(Catholic University of America,Washington, DC 20064) The Shoreor IRHD hardnesstest has beenwidely usedfor many The characterizationof viscoelasticpolymers frequently requires de- yearsand hasbecome one of the standardsfor characterizingmaterials termination of the static toodull in addition to determination of the in the rubberand plasticsindustries. The obtainedhardness scale val- dynamic moduli. A commonly applied method for determiningthe ues,ASTM or IRHD, are oftenrelated to the staticelastic properties of staticYoung's or shearmodulus is to extrapolatethe dynamicmodulus rubber-likematerials. The classicalHertz equationhas also been used to in the rubberyregime to vanishinglow frequency.A secondapproach is correlatethe hardnessscale values to the staticelastic properties. Re- to relate the hardness,e.g., ShoreA, to an estimateof the Young'sor cently, progresshas been made on the problemof obtainingdynamic ciscoelasticproperties through the useof a vibratingspherical indentor shearmodulus. As will be brieflydescribed, neither of theseapproaches and modelingthe measuredinput impedanceby the radiationimped- appearsto provide consistentresults. A method is describedthat ex- anceof a sphereradiating into a half-space.In the limitingcase where ploitsthe stress/strainhysteresis loop to developestimates of the static the sphereradius is small,such that ka• 1 for longitudinalwaves, it is moduli.The methodis believedto providemore reliable estimates than shownthat the measuredshear modulus and lossfactor are in good obtainablefrom the previouslyemployed methods. Examples are pro- agreementwith that found usingother dynamicmethods such aa the videdof the method'sapplication to a varietyof ciscoelasticpolymers DMTA or the resonancemethod. The modelis most appropriatefor lX•sessingloss factors varying from about0.1-1.0, and rubberymoduli relativelysoft materials or very thick hard materialswhere the thickness varyingfrom 1-10 Mpa. Comparisonsare madebetween the resultsof of the materialcan be ignored.The problemof very hard materialsand the new methodand the two previouslyused ones. [Work supportedby finite thicknesswhere the terminatingboundary is important will be ONR 1225AM.] discussed.

1780 d. Acoust.Soc. Am.,Vol. 94, No. 3, Pt. 2, Sept. 1993 126th Meeting:Acoustical Society of America 1780 TUESDAY MORNING, 5 OCTOBER 1993 MAJESTIC BALLROOM, 8:30 TO 11:45 A.M.

Session 2aSP

SpeechCommunication: Applications of SpeechProduction Research in DisorderedPopulations

Abeer Alwan, Chair Departmentof ElectricalEngineering, 66-147E Engr. IF;, Universityof California,405 Hilgard Avenue,Los/•ngeles, California 90024

ContributedPapers

9:00

2aSPI. Aerodynamic and acoustic changesfollowing inteusive voice 2aSP3. Spectx'almyoelectric analysis of thyroarytenoidactivity in therapy for patients with Parkinson's disease: A case study. normaland spasmodic dysphonia subjects. Rick M. Roark (Dept. of ChristopherDromey, LorraineO. Ramig (Recordingand Res. Ctr., Otolaryngol.,New York Medical College,Munger 170, ¾alhalla,NY 1245 Champa St., Denver, CO 80204, and CDSS Dept., Univ. of 10595), Eric M. Dowling, Ronald D. DeC}roat (Univ. of Texas, Colorado,Boulder, CO), and Ronald Scherer (Recordingand Res. Dallas, TX}, Ben C. Watson, and Steven D. Schaefer (New York Ctr., Denver, CO) Medical College,Valhalla, NY} Time-synchronousdigital recordings of thyroarytenoid(TA) myo- A 50-year-oldpatient with Parkinson'sdisease received a 4-week electric activity (via percutaneoushooked-wire electrodes) were ob- courseof intensivevoice and respiratorytherapy aimed at improving tainedfor 10 normalcontrol and 11 spasmodicdysphonia subjects dur- functionalcommunication through increasediaryngeal adduction. ing performanceof five vocal tract tasks of increasingmoteric Aerodynamicand acousticdata weregathered on two occasionsbefore complexity:(i) quietbreathing, (2) Volsalvomaneuver, (3) whispered treatment,two after the completionof therapy,and at 6- and 12-month [il, (4) voicedI i , and(5) Beepbeep went the heap. Three-dimensional follow-upsessions. There wereincreases in sobglottalpressure and ia- powerspectral density functions, PSD(f,t), were determinedfor a ryngealairway resistanceafter the treatment. Maximum flow declina- leeredsegment of the signals,and measuresof medianfrequency, mean tion rate (MFDR) also increased,as did the soundpressure level of frequency,bandwidth, and centerfrequency of PSD(f,t) werederived utterancesthat the subjectproduced at a "comfortable"effort level. for each sample point. Statisticalmedian, mean, standard deviation, Fundamentalfrequency variability and conversationalintensity levels maximum,minimum, and modeof the PSD measureswere computedto were higher post therapy. Video-stroboscopicexamination before and composefeature vectors for eachsignal. Discriminate analysis and max- imum likelihood classificationtests were applied to obtain global dis- after treatment showedimprovements in adduction and a decreased crimination measuresfor the two subjectpopulations as a function of level of supraglottichyperfunction. Possible physiological mechanisms taskperformance. Results of the analysisare reportedthat reveala task are discussedto accountfor thesechanges. [Work supportedby NIH effect.Graphical presentations of TA myoelcctricand speechacoustic Grant No. R01 DC01150-03and NIDCD Grant No. DC00976.] signalswith accompanyingtime-frequency PSD plotsare given.Com- parisonsare made amongincidents of spasmand nonspasm,posing questionsinto physiologicmeaning and basis of spectral- versus 8:45 amplitude-definedlaryngeal muscle spasms. [Work supportedby NIH Grant No. DC00410 and NSF Grant No. MIP9203296.] 2aSP2. The effect of intensive voice therapy on speech and voice deficits in atypical Parkinson's disease. Stefanie M. Countryman (Recordingand Res. Ctr., 1245 ChampaSt., Denver, CO 80204) and 9:15 LorraineO. Ramig (Univ. of Colorado,Boulder, CO} 2aSP4. Quantitative analysesof thyroarytenoid activity in spasmodic dysphonia. Ben C. Watson,Rick Rnark, and StevenSchaefer (Dept. Acoustic data were collected twice pre-treatment, once post- of Otolaryngol.,Munger, Rm. 170, New York Medical College, treatment, and 6 monthspost-treatment on three atypical Parkinson's Valhalla, NY 10595) diseasepatients following intensive voice therapy. Using a custom-built softwareprogram, the followingvariables were measured:maximum Perceptualratings of vocal abnormalityin spasmodicdysphonia (SD) are confoundedby high variabilityin the severity,quality (strain- duration of sustainedvowel phonationand sound pressurelevel from strangleversus aspirate}, and tasksensitivity of symptoms.Perceptual sustainedvowel phonation, a standardpassage, and spontaneousspeech. ratingsare also relativelydistant from the physiologicsource of vocal Using the C-Speechapplication [Milenkovic, $. SpeechHear. Res. 30, disruption.Investigations at the neuromuscularlevel are closerto the 529-538 ( 1987)], fundamentalfrequency variability was measured from sourceof disruption and may be informative. Thyroarytenoid myoelec- a standardpassage and spontaneousspeech. Single-word intelligibility tric activity was recordedwhile SD and normal control subjectspro- wascalculated using naive listeners' perceptions. The patientsachieved dueedmultiple tokensof sustainedvowel, word repetition,and sentence statisticallysignificant improvement on all variablespost-treatment but tasks.Quantitative amplitude measures were submitted to severalprin- did not maintainimprovement as a groupduring readingand sponta- cipalcomponents analyses to developmodels of neuromotorabnormal- neousspeech by the 6.monthdata collectionsession. These results sug- ity in SD. Analysesyielded quantitative indices of the magnitudeand gestthe effectiveness of intensive voice treatment in atypicalParkinson's task-sensitivityof thyroarytenoidactivity. A between-groupmodel that diseaseas well asprovide insight into the underlyingpathophysiology of included one measure across the three tasks achieved 100% discrimi- their speechand voicedeficits. Due to the limitedlength of time post- nation of normal control and SD subjectson one component.The treatmentlevels were maintained,a longer period of therapyas well as within-groupmodel failed to separateperoeptually different subgroups follow-uptherapy sessions are recommended for thispopulation. [Work of SD subjectsalong either componentconsidered separately. Models supportedby NIH Grant No. ROI DC01150-03and NIDCD Grant challengethe validity of the traditional clinical distinctionbetween ab- No. DC00976.] ductor and adductorSD and the validity of perceptualratings of vocal

1781 J. Acoust. Sec. Am., Vol_94, No_3, Pt. 2, Sept. 1993 126th Meeting: AcousticalSociety of America 178 spasmsin spasmodicdysphonia. [Work supported by NIH Grant No. examinedin detail.The analysisand testinghave led to severalconclu- DC-00410.] sionsconcerning the control of the articulatorsfor this speaker:pra- ductionof obstruentconsonants was a particularproblem (only 30% of syllable-initialobstruents were producedwith no error), whereassono- rant consonantswere lessof a problem(70% correct). Of the obstruent 2aSPS. Comparisonbetween clinicjan-assistedand computer-assisted errors, most were voicingerrors, but place errors for alveolars(partic- methodsfor obtaining the voice range profile. Darrell Wong, Susan ularly fricafives) were also high, and theseconsonants were produced Hensley (Recordingand Res. Ctr., Denver Ctr. for the Performing inconsistently,as inferred from acousticanalysis and from low scores Arts, 1245Champs St., Denver,CO 80204), Ingo Titze (Recording from the recognizerfor wordswith theseconsonants. In comparison, Res. Ctr., Denver, CO and Univ. of Iowa), Lorraine O. Ramig vowel errors were lessprevalent. Implications for the use of a speech (RecordingRes. Ctr., Denver,CO and Univ. of Colorado,Boulder, recognizerfor augmentingthis speaker'scommunication abilities are CO), and Martin Milder (Univ. of Iowa) discussed.

A studywas made comparing two methodsfor obtainingthe voice rangeprofile, a clinicaltool used to establisha subject's range of inten- 10.-45 sity and fundamentalfrequency. One methodused a clinicJanwith a pitchpipe to elicitand motivate the subject.The othermethod used an 2nSPS. Phonatory instability in ALS dysarthria: A ease study. instructionalvideotape and a computer.The computerwas completely Eugene H. Buder (Dept. of Speech and Hear. Sci., Univ. of automated,providing visual feedback of the voice rangeprofile, and Washington,JG-15, 1417 NE 42nd St., Seattle, WA 98195) and evaluatingeach phonafion objectively using the criterion of fundamen- EdytheA. Strand (Univ. of Washington) tal frequencystability, intensity stability, and duration.The computer- A subgroupof patientswith dysarthriaresulting from amyotrophic izod methodused a cepstrumalgorithm to estimatefundamental fre- lateralsclerosis (ALS) presentswith voiceproblems characterized pri- quency,and the intensity was measured by calculatingthe variance of marilyby cycle-to-cycleand long-termphonatory instabilities. This pa- the signal.The resultspresented here compare the two methodsand per reportsacoustic analyses of the phonationof a 63-yr-oldfemale 9 discussthe benefitsand drawbacksof each approach.Benefits of the monthspost diagnosis of ALS. Perceptualcharacteristics of voicein- computerizedmethod include real time visualfeedback of phonatory eluded inconsistentharshness and cyclic variationsin both pitch and effort,objective acceptability criterion, and no requirementto phonatc loudness.Spectral analysis of fundamentalfrequency (f0) andintensity at pitchesin any particularorder. A drawbackto the computerized contoursrevealed periodic instabilities at multiple temporaldomains, method is its sensitivityto subharmonics.[Work supportedby NIH including0.4- and 0.8- Hz cyclesin both f0 and intensity ("wow"), Grant No. DC00(}-387.] 2-Hz cyclesin f0 ("tremor"), and ! l-Hz cyclesin intensity("flutter"). Phaserelations were notedamong these cycles and with other acoustic 9.'45 analysisparameters such as perturbationand spectralenergy distribu- tion, indicatingthat occurrenceof short-termand cycle-to-cycleinsta- 2aSP6. A microcomputer-basedclinical voice aerodynamic bilitieswas modulatedby the longerterm cycles.The resultsare dis- me•urementsystem. BruceJ. Poburka (Dept. of Commun.Disord., cussedwith relationto videostroboscopic examinations of thispatient, Univ. of Wisconsin,1500 Highland Ave., Rm. 461, Madison, WI andalso in comparisonwith phonatorycharacteristics of other patients 53705), Paul H. IViilenkovic,and Diane M. Bless (University of in this subgroup(females with ALS relatedvoice problems). [Work Wisconsin,Madison, WI 53705) supportedby NIH.] The authors' clinical experiencewith dedicatedinstruments for

voice aerodynamicmeasurements prompts them to implementthese 11.'00 measurementson a microcomputersystem. A microcomputersystem can be lower in cost,it facilitatesarchival storage of data, it offersthe 2aSP9. Acoustic analysis and synthesis of pathological voice flexibilityof changingwhat is measuredand it offersautomated post qualifies. Christopher Long, Phil Bangayan, and Abecr Alwan processing.A systemmeasuring flow, intensity, intraoral pressure, and (Dept. of Elec.Eng., 66-147E Engr. IV, UCLA, 405 HilgardAve., Los pitchis implementedon a PC compatiblecomputer, using an Intel 486 Angeles,CA 90024-15940) microprocessor,running the CSpcechwaveform acquisition and analy- sis software.The salientenhancements to CSPeechused to implement An analysis-by-synthesisapproach was adopted to classifythe thissystem are described. The recordcommand was modified to provide acousticand perceptualfeatures of three pathologicalvoice qualities: visualfeedback of voiceaerodynamic eflleiency, and a pause/resume breathy,strained, and rough.One hundredand sixty waveformsof the featuresimplifies clinical voice recording procedures. Filter scriptswere vowel/u/spoken by female and male subjectswith pathologicalvoice developedto providea flexibleway to specifyanalysis procedures and qualitieswere obtainedfrom the VA Hospitalin West LA. The tempo- formats for archival storageand retrieval. The filter script is basedon ral and spectral featuresof the waveforms were studied and the results the object-orientedconcept of specifyingboth the data and a methodfor were usedin synthesizingthe utterancesusing the Klatt formant syn- analyzingor archivingthe data in the desiredform. thesizer.Preliminary resultson 30 breathy and strainedvoices indicate that the perceptionof "pathological"breathiness is mainly relatedto: (1} a large open quotient of the glottal waveform (OQ) and (2) the 10:00-10:.30 Break amplitudeof aspirationnoise (AH} relativeto that of voicing(AV) with femalevoices exhibiting a larger (AH-AV) than male voices.For 10:.;30 somevoices, it wasalso necessary to introduceextra poles to the vocal- tract transferfunction to achievea better spectralmatch. Synthesisof 2aSP7.Speech input for dysarthrieusers. Hwa-PingChang (Dept. of strainedvoices required a lower OQ than that neededfor normal voices Mech. Eng. and Res. Lab. of Electron.,MIT, Cambridge,MA 02139) and, in somecases, amplitude and/or frequencymodulation was intro- duced to achieve a better match in the time domain. The synthetic One practicalaim of this researchis to determinehow best to use speechrecognition techniques for augmentingthe communicationabil- voiceswere judged perceptually by cliniciansto be of high quality.The ities of dysarthricspeakers. As a first step toward this goal, the follow- results will be discussedin terms of the effects of different vibratory ing kindsof analysesand testshave been performed on wordsproduced patternsof the vocal folds on the acousticspeech waveform. by severaldysarthric speakers: a closed-setintelligibility test basedon Kent et al. [J. SpeechHear. Disord. 54, 482-499 (1989)]; an open 11:15 intelligibility test; critical listeningand transcription;acoustic analysis of selectedutterances; and an evaluationof the recognitionof wordsby 2aSPIO. Measurement accuracy of the Glottal Enterprises a commercialspeech recognizer. The data from one speakerhave been pneumotachsystem. Ronald C. Seherer,Christopher Dromey, and

1782 J. Acoust.Soc. Am., Vol. 94, No. 3, Pt. 2, Sept. 1993 126th Meeting:Acoustical Society of America 1782 Chwen-GengGuo (The Denver Ctr. for the PerformingArts, 1245 of Wisconsin, 1500 Highland Ave., Rm. 461, Madison, WI 53705), ChampaSt., Denver,CO 80204) Paul H. Milenkovic,and Diane M. Bless (University of Wisconsin, Madison, W! 53705) An importantinstrument for measuringairflows in speechis the pneumotachsystem provided by Glottai Enterprises.Inverse filtering the measuredairflow allows the estimationof glottalvolume velocity. The measurementof aperiodicitynoise in the humanvoice is com- The facemask {MSIF-2) has numerouswire-meshed holes placed ap- plicatedby the multiplesource of this noise.While turbulencenoise at proximatelyin the planeof the lips. Airflow from the mouth during the glottis is hypothesizedto contributeto aperiodieitynoise, it is speechmay cameout in a directedstream, creating nonuniform flow known that waveformjitter, the cycle-to-cyclefluctuation in pitch pe- throughthe mask and measuredpressures (Micro Switch) that do not riod, contributessignificantly to the measuredaperiodicity noise. In reflectthe correctflow. Resultsfor cylindricaltubes representing mouth seekingto reducethe influenceof jitter on measurednoise, it has been openingsindicate that the angleof the flowmakes a difference:e.g., for observedthat a cross-correlationpitch trackerbased on a slidinganal- a flowof about700 cc/s projectingupward versus downward at 45-deg ysiswindow exhibits the greatestchange in measuredpitch period when angles,the differencein estimatedflow is 100-250 cc/s for a small tube opening(0.2 sqcm}. The differenceis only about10 ce/s for a medium the windowcrosses a glottal-closureepoch. It washypothesized that the sizemouth opening of 2.0 sqcm. Also,results indicate that equipment accuracyof a pitch-predictorbased measurement of the noisecould be drift is a minorconcern, flow estimatesare negligiblydifferent for the improvedif one knew the correctalignment of the analysiswindow eapectedrange of faceprotrusions into the maskfor the mediummouth relativeto the glottaiepoch. In the absenceof this knowledge,for each opening,and the effectsof temperaturechange were negligible. Results updateof a short-termanalysis, two alignmentsof the windowwere will bediscussed relative to the accuracyof flowmeasures for particular usedand that alignmentwith the least-squarepitch predictorerror was speechand voicesounds. selected.This leadsto a computationallyefficient algorithm that does not requireexplicit determination of glottalepochs. Preliminary trials 11:30 on subjectswith highSNRs indicatea reducedinfluence of jitter on the oh.served SNRs. 2pSPll, A two-tappitch predictorfor measuringvoice aperiodicity noiseat high SNR. Mark Leddy (Dept. of Commun.Disord., Univ.

TUESDAY MORNING, 5 OCTOBER 1993 COLUMBINE ROOM, 7:55 TO 11:30 A.M.

Session 2aUW

Underwater Acoustics:Scattering and ReverberationII

StanleyA. Chin-Bing,Chair NavalResearch Laboratory, Stennis Space Center, Mississippi 39529

C!'s Introductions7:55

ContributedPapers

2aUW2. Abstract withdrawn.

2al_F•l. Low-frequencytime-dependent scattering from evolving bubbleplumes: Theory and numericalresults. Robert F. Gragg and Daniel Wurmser (Naval Res. Lab., Code 7144, Washington,DC 20375-5350)

This work advancesthe capabilityfor modelingthe scatteringfrom near-surfacebubble plumes beyond the static approximation.Plumes were modeledas evolvingstructures having finite lifetimes (- l0 s) 8:15 with distinctgrowth and decaystages. The scatteringresponse of such a plumewas formulated in termsof the theoryof linear time-varying 2alYW3. A sparseboundary-element method for seatteringfrom a (LTV) filters.Complex scattering amplitudes within the frequency rigid body of revolution. Erik M. Rosen (SFA, Inc., 1401 bandof interest(50-500 Hz) werecomputed using either panini wave McCormick Dr., Landover,MD 20785), Luise S. Couchman (Naval analysis[for (hemi-) sphericalshapes] or boundaryintegral equation Res. Lab., Washington,DC 20375), and Francis X. Canning (BIE) methods(for more generalshapes). For cw inputs,groups of (Rockwell Sei. Ctr., Thou•nd Oaks, CA 91360) pseudo-Dopplerside peakswere observedin the scatteredspectra as a result of the time evolutionof the targct'sinternal resonances.Several A sparseboundary-element method is usedto calculatethe scattered broadband source waveforms were considered to assess their effective- acousticfield of a rigid body of revolution.The NXN full matrix re- nessas experimentalprobes for observingtransient near-surface plumes sultingfrom the discretizationof the Helmholtzintegral is transformed in the field.['Work supported by ONR, Code 4530.] to a sparseNXN matrix using the impedancematrix locali7ation

1783 J. Acoust.Soc. Am., Vol. 94, No. 3, Pt. 2, Sept. 1993 126th Meeting:Acoustical Society of America 1783 (IML) method. When appliedto integral equationsfor wave phenom- erned by a variety of near-surfaceeffects. Principle among these are ena, the IML method producesa sparsematrix by partitioningthe microbubbledistributions and their subsequenteffects on the local scattererinto severalregions, over whichthe responseis representedby soundspeed structure. Although a rigorousexplanation of thesescat- basisfunctions with directional radiation patterns.The number of im- teringresults (including the presenceof spikeyevents often observed in portant physicalinteractions is reducedto a small numberover each both deepwater scattering experiments and sonartrials) wouldlikely region,leaving a largenumber of matrix elementswith relativemagni- requireconsideration of a host of physicalacoustic mechanisms, Oc- tudesless than 10 -4 whichcan be approximated byzero. Used in con- cum'srazor woulddictate that a simpleexplanation can be both effec- junction with existingBEM codes,the IML methodreduces the mem- tiveand illuminating. This paperexamines the roleof monopoleradia- oryand storage requirements from N • toapproximately 100N, while the tors, the simplestform of radiation,beneath a roughpressure-release solutiontime is O(N} comparedto O(N•} for thefull untrausformed surfaceto explainthe presenceof low-frequencyfalse targets. It is case.The resultingsparse matrix can be approximatelyinverted leading shownthat for certainsea state conditions such false targets can result to a convergentsolution in lessthan five iterations.Results are givenfor from transientbubble plumes acting as acousticallycompact scatterers. scatteringfrom a hemisphericallyendcapped cylinder of L/a= 110 for An attemptwill alsobe madeto estimate,from the combinedprobabil- ka=l to ks= 17. itiesof the presenceof white capsand the likelihoodthat a givenbubble plumepossesses the requisitevolume fraction to producesuch an event, the numberof falsetargets to be expectedas a functionof sea state. 8:,30 [Work supportedby ONR and ARPA.]

2aUW4. Multiple scattering effects in scattering from a target in shallowwater. Angie Sarkissian (Naval Res. Lab., Washington,DC 20375-5350) 9:15 Scatteringfrom a targetin a boundedmedium involves both prop- agationeffects and targetscattering effects as well as the couplingof the 2aUW7. Quantitative backscatteringcoefficients from the numerical two. Previously,in order to simplythe problem,the couplingof the two scatteringchamber. R. A. Stephenand S. A. Swift (Dept. of Geol. effectshad beenneglected by ignoringthe contributionof multiple scat- and Ocophys.,Woods Hole Oceanogr.Inst., WoodsHole, MA 02543) tering betweentarget and shallow water boundaries.This has been Models of geoacousticinteraction with the seafloorare essentialto highly desirablebecause it eliminatesthe needto evaluatethe shallow link the backscatteredacoustic field with geologicaland geophysical water Green's function over short ranges.Scattering computations are descriptionsof the seafloor.Beamforming has beenimplemented into madeto showthe importanceof includingthis couplingeffect even at numericalscattering chamber formulation so that backscattercoeffi- relativelylow frequencies.It is shownthat if the targetis closerto the cientsand functionscan be obtained.This processis discussedfor a flat, surfacethan the bottom, then the main contributionof the multiple homogeneousseafloor; a singlefacet on a flat, homogeneousseafloor; scatteringis dueto the interactionof the targetwith the top surfaceand and a canonicallyrough, homogeneousseafloor. This study suggests this effectmay easilybe includedwhen the methodof superpositionis that representingthe backscatteredfield by a single,angle-dependent applied. coefficientis an oversimplification.Coherence of the scatteredfield acrossthe beambefore stacking and the time spreadof the stackedfield are significantissues. The numericalstacking chamber computes solu- tionsto the elastic(or anelastic)wave equation by the finite difference 2aLFOVS.Predicting bistatic target scattering from monostatle data. method in a two-dimensionalCartesian geometry. The finite difference Harr• A. Schenck [Code 702(S), RDT&E Div., Naval Command approachhas the following advantages:(a} it includesall shear wave Control and Ocean SurveillanceCtr., San Diego, CA 92152-7520] {rigidity) effectsin the bottom;(b) it can be appliedto pulsebeams at low grazing angles;(c) both forward-scatterand backscatterare in- Characterizingbistatic scattering from a targetfor many anglesof cluded; (d) multiple interactionsbetween scatterers are included; (e) incidenceis expensiveand time consumingeven in ideal laboratory arbitrary,range-dependent topography and volumeheterogeneity can conditions,and essentiallyinfeasible in an operationalenvironment. be treatedsimultaneously; (f} problemsare sealedto wavelengthsand Consequently,extending the value of monostaticdata by using it to periods;and (g) the methodconsiders scattering from structureswith estimatethe bistatictarget strengthis extremelydesirable. Previous lengthscales on the orderof acousticwavelengths. effortsto do thishave severe limitations or restrictionsin their applica- bility. A new techniquethat combinesnumerical modeling and experi- ment will be described.The crux of this methodis to rely on modeling to supplythe far-fieldpropagator function that predictsthe scatteringin any directionwhen the surfacevalues are known, and to determinethe 9:30 surfacevalues by least-squaresapproximation from knowledgeof the 2aUWS. Bottom backscatteringstrengths derived from shallow-water monnstaticscattering and the principleof reciprocity(which requires reverberation measurements. Dale D. Ellis and John R. Preston the scatteringmatrix to be symmetric).An examplewill be shownin (SACLANT Undersea Res. Ctr., Viale San Bartolomeo 400, 19138 La which the completethree-dimensional scattering field was estimated for Spezia,Italy) a rigid axisymmetricbody given only the monostatictarget strength at anglesin one planefrom 0 to 180 dec. Rules that relate the numberof A normal-modemodel for calculatingsurface and bottom reverber- monostaticabservations needed to the frequencyand the complexityof ation in shallowwater has beendeveloped, and foundto give good the target will be described.The extensionof this techniqueto nonrigid agreementwith single-hydrophonedata for a fairly fiat-bottom•xlarea scatterers will be discussed. [D. D. Ellis, SACLANTCEN ReportSR-196 (September1992}]. The model has beenextended to includebeam patterns and has beencom- pared with broadbanddata receivedon a horizontal line array. The model-dataagreement is againgenerally quite good.When the model- data differencesas a functionof beamangle and time are overlaidon a 2aUW6. Low-fr•uency backscatterfrom near-•urfaeebubble plumes. mapof thearea, the differences are seen to beprimarily due to changes JeffreyA. Schindall (Dept. of Phys.,Univ. of Mississippi,Univemity, in the bottom bathymetry.This can be usedto extract a measureof the MS 38677), Ronald A. Roy, Lawrence A. Crum (Univ. of bottom backscatteringstrength versus location. Washington,Seattle, WA 98105),and WilliamM. Carey (DARPA, Arlington, VA 22203}

Anomalouslow-frequency backscatter from the seasurface is gov- 9:45--10:00 Break

1784 J. AcousL Soc. Am., VoL 94, No. 3, Pt. 2, Sept. 1993 126th Meeting:Acoustical Society of America 1784 10..00 low-frequencyactive reverberation data collected in the CentralArctic in 1992where such an inversionyields meaningful results and compare 2aUW9. Reflections and diffractions from fncet-wedgeco •ructions: themto theoreticalpredictions. Historical and measured ice roughness Acousticexperfments nntl theory. Saimu Li (Dept. of Geol. and statisticscollected in tandemwith the acousticportion of the experi- Oeophys.,Weeks Hall, Univ. of Wisconsin,Madison, WI 53706), ment were used to obtain elastic perturbationtheory predictionsof DeZhang Chu (Woods Hole Oceanogr.Inst., Woods Hole, MA scatteringloss and backscatter.These losseswere integratedinto the 02543), and C. S. Clay (University of Wisconsin, Madison, WI Kraken normal mode model to yield highly accuratepredictions of the 53706) coherentsignal structure to very longranges in the Arctic waveguide,as The higher-orderdiffractions of transientpressure signal from a verifiedby TL measurements.Based on thesepredictions, a significant combinationof hard finite facetwedge of 45 deg and an infiniteplane portionof the time/frequencystructure of the backscatteredreturn re- havebeen studied experimentally and theoretically.Experiments used a ceivedon a 256-elementhydrophone array wasmodeled. To constructa spark point sourcewith a separatedreceiver at the sameside of the well-conditionedinverse problem, propagation in 10-Hz bandswas di- wedge.The reflectedpressure signals were well separatedin time do- vided into three distinctgroups; surface duct, mid depth and RSR. main.Higher-order diffractions from the apexand troughs of the wedge Modelingof TL andtravel time for eachband/group made it possibleto were observed. The studies were concentrated on the reflections from invert the energyin the backscatteredreturn for the averagescattering the facetsand the diffractions.The experimentalgeometry is different crosssection of the ice coverat the threediscrete group grazing angles. from Medwineta/. [I. Acoust.Soc. Am. 83, 1794-1803(1988)]. Biot Comparisonof the derivedscattering strengths with the elasticpertur- and Tolstoy's exact wedge solution [J. Acoust. Soc. Am. 29, 381 bation theory predictionsyielded good agreement. [Work supportedby {1957)] and extensionswere usedto compareexperimental data and ONR.] theory. 11:00 10:lS 2aUWI3. A spectral method for calculation of ocean acoustic normal 2aUWI0. Simulation of propagation and scattering in a waveguide modesusing Chebyshev polynomials. Matthew A. Dzieciuch (Scripps with a combined parabolic equation/extended boundary condition Inst. of Occanogr., IGPP-0225, UCSD, La Jolla, CA 92093} model. R.A. Zingarelli (Naval Res. Lab., AcousticsSimulation Sec., A new methodemploying Chebysbev polynomials to calculatethe StennisSpace Center, MS 39529) underwateracoustic normal mode equation was developed. The method By usingthe parabolicequation for range-dependentwaveguide is a spectralapproach using Chebyshev polynomials as basisfunctions. propagation,the extendedboundary condition model for objectscatter- This expansionhas the advantageof beinga particularlyefficient and ing, and a new method for couplingthe two models,b•csin-scale active accuraterepresentation of the normal modes(especially of the lower acousticsimulations have been performed.The transformationsand order} sincethey give an exceedinglygood representationof narrow algorithms,as well as someresults, will be presented.[Work supported boundarylayers such as the sound-speedprofile that can undergorapid by ONR.] changesnear the surface.This representationreduces the size of the eigenvalueproblem to besolved. Since the CPU timescales with N s, where N is the size of the matrix, any size reductionis an advantage 10-,a0 computationally.This approachhas a significantspeed advantage over 2aUWII. A null field T-matrix perturbation formalism for scattering finite differencemethods without sacrificingaccuracy. A Chebyshev from n fluid-elastic interface with random surface roughness. representationis usually remarkably close to the minimaxpolynomial Garner C. Bishop (Naval UnderseaWarfare Ctr., Div. Newport, that minimizesthe maximumerror implyinghigh accuracy.Chebyshev Newport,RI 02840) polynomialsare alsouseful for the calculationof quantitiesinvolving the integralof the modefunction, such as modalgroup velocity, loss, A null field perturbationformalism for scatteringa pressurewave and couplingeoc•icient matrices in non-adiabaticpropagation environ- from a fluid-elasticinterface with random surfaceroughness is devel- ments.These quantitiescan be calculatedeasily and accuratelygiven oped. Helmholtz-Kirchhoff integral equationsand the elastic tensor their spectralrepresentations without introducing any furthernumerical boundaryconditions are usedto representthe unknownscattered and error. surfacepressure and displacementfields. The null field hypothesisis usedto obtaina systemof coupledintegral equations for the surface 11:15 fields.Perturbative representations of the scatteredand surfacefields and of the matrixelements of the Helmholtz-Kirchhoffintegral equa- 2aUWI4. A normal-mode theory of shallow-water reverberation. tionsare constructedand usedto developequations for the nth-order Reohe Zhang (State Key Lab. of Acoust., ChineseAcad. of Sci., spectralamplitudes of theunknown fields. It isshown that the nth-order Beijing100080, People's Republic of China}, GuoliangJin, Dinghua spectralamplitude of a scatteredfield is coupledto the nth-orderspec- Guan, WenhuaLi, and XinfangQiu (ShanghaiAcoust. Lab., Chinese tral amplitudesof all scatteredfields and to all lower-orderspectral Aead. of Sci.,Shanghai 200032, People's Republic of China) amplitudesof all surfacefields. Consequently, the nth-order T-matrix may be calculatedreeursively and expressedin termsof the zeroth-order Shallow-waterreverberation is mainly causedby bottom scattering, off-shell T-matrix elements.The T matrix for the nth-order spectral and is much morecomplicated than the deep-waterone. Ray theorycan amplitudeof the scatteredpressure field in the fluid is calculated,and it be usedfor calculatingshort-range reverberation simply by ignoringthe is shownthat scatteringprocess is mediatedby excitationof all possible water inhomogeneity,but is not suitablefor long-rangereverberation intermediate surface states created by mode conversionof all lower- due to effectsof refraction and multipath transmission.Assuming that order surface field states. the scatteringsources are homogeneouslydistributed on the bottomand regardedas the secondarysound sources with certaindirectivity, by usingthe WKBZ approximationa normal-modetheory suitablefor 10:45 long-rangereverberation is developed.Because the effectsof the com- plex eigenvalueson the modeincident field have beenconsidered, the 2aUW12. Modeling and analysis of low-angle ice canopy theory is better than the former ones.The givenexpressions of rever- reverberationin the Arctic, Oreg Duckworth, Ted Farrell, Kevin LcPagc, and Cola Atkinaon (Bolt Bcranck and Ne:wman, Inc., 70 berationintensity have explicit physical meaning and conciseform so that they are easilyused for numericalcalculation and analylicaldis- FawcettSt., Cambridge,MA 02138) cussion.Both theory and experimentshow that the reverberationin Recentadvances in modelingcoherent loss in the Arctic have made inhomogeneousshallow water hasobvious depth dependence and there it possibleto attempta constrainedinversion of monostaticArctic re- existsthe relationship: IR(r,z, ,z2)=[IR{r,z •,z•)XIR(r, z2,z:)] '/2. Some verberationfor the ice scatteringmatrix. An analysisis presentedof experimentalresults are giventhat are consistentwith theory.

1785 J. Acoust.Soc. Am., Vol. 94, No. 3, Pt. 2, Sept. 1993 126th Meeting:Acoustical Society of America 1785 TUESDAY AFTERNOON, 5 OCTOBER 1993 TERRACE ROOM, 12:55 TO 5:00 P.M.

Session2pAO

AcousticalOceanography: Determination of OceanicParameters from Scatteringin Ocean Waveguides

E. C. Shang,Cochair CIRES, Universityof Colorado,NOAA WPL, 325 Broadway,Boulder, Colorado80303

JamesF. Lynch, Coohair Departmentof AppliedOcean Physics and Engineering,Woods Hole OceanographicInstitute, WoodsHole, Massachusetts 02543

Chair's [ntFoduction--12:S5

Invited Papers

1:00

2pAOl. Longvertical m't•ys in acousticalsounding of the ocean. A. Voronovicha• (Wave PropagationLab./NOAA/ Environmental Res. Labs., Boulder, CO 80303)

Usinglong vertical arrays (LVAs) in oceanacoustics enables one to measurean S matrixdescribing transformations of modes in inhomogeneouswaveguides. The S matrix allowsone not only to calculatethe soundfield for any configurationof sourcesand receiversbut alsoto proceedto the solutionof the inverseproblem (IP)--retrieving inhomogeneitiesfrom acousticaldata. The wave-typeIP is.studiedfor the I-D case,which differs significantly from the multidimensionalsituation. For instance,in the 2-D case,the IP can be solvedbased only on the submatrixdescribing forward scatteringas a functionof frequency.The 2-D irregularitiesin the acousticwaveguide could be reconstructedas in the I-D problemwith the help of the layer-peelingalgorithm via backscatteringdata. But this approachis of little practical usebecause backscattering is usually weak. Practical formulation of the deterministicIP in oceanacoustics should exploit some final-dimensional description of the mediaand useall availabledata about the $ matrix. For example,using phasesof diagonalelements measured at only two close frequenciesleads to the Munk-Wunschscheme of modalocean tomography. In the generalcase, a numerical-evolution-typealgorithm is proposedto solvethis nonlinear problem in the spiritof the invariantimbedding approach. [Work supported by NRC andPPSIO of Russia.] •)Onleave from the P. P. ShirsbovInstitute of Oceanology,Moscow, Russia.

1:25

2pAO2. Renormalizationof prolmgationin layered media with rough interfaces. David H. Betman (Dept. of Phys. and Astron.,Univ. of Iowa, Iowa City, IA 52242)

There are now a numberof goodapproximations for plane-wavescattering from roughinterfaces separating two half-spaces. This work will describehow theseapproximations can be usedwhen there are two or more roughinterfaces. The techniqueto be developedis basedon matchingapproximate scattering states, expressed in terms of half-spacescattering amplitudes, across sourceplanes. Boundary conditions at interfacesare satisfiedby the scatteringstates. It will be shownhow the resulting descriptioncan be renofinalizedso that the mean field is describedin terms of effectivereflection coefficients at the interfaces, whichare distinctfrom coherenthalf-space scattering amplitudes. It will alsobe shownthat the methodof smoothinggives a first-orderapproximation to a fully tenorrealizedmean field. Expressionsfor effectivemodal attentnationswill alsobe derived.

l:S0

2pAO3. Relation betweenwaveguide and nonwaveguide(half-space) scattering from a rough interface. T. F. Gao (Inst. of Acoust., AcademiaSinica, Beijing, People'sRepublic of China) and E. C. Shang (Univ. of Colorado/NOAA/Wave Propagation,Boulder, CO 80303)

A formalsolution of thescattering field from a roughinterface has been derived. Under the Bassperturbation theory, both waveguideand nonwaveguide (half-space) scattering from a roughinterface (the seabottom) can be calculatedanalytically. By usingan identical definition of"scattering coefficient," a relation between the waveguide scattering (the modal S matrix)M• 0 and thenonwaveguide scattering (conventional plane-wave scattering) coefficient ms has been found: M•0= (2•r)2rn/[ V(Ot) V(O i ) I, whereV(Ot) and V(O i) representthe reflection coefficients of the plane interface for themodal incident angles Ot and 0 i, respectively.Consequently, based on thisrelation, the r%data measured in theconventional sense (half-space) can be bridged into a shallowwater reverberationprediction or vice versa.

1786 J. Acoust.Soc. Am., Vol. 94, No. 3, Pt. 2, Sept. 1993 126th Meeting:Acoustical Society of Amedca 1786 2:15

2pAO4.Scattering from frontal strnc•ures,internal fides, and internalwaves during the 1992 BareatsSea polar front exper/ment.Ch/ng-Sang Chin, JamesH. Miller (Naval PostgraduateSchool, Monterey, CA 93943), GuoliangJin, DouglasRay, andJames Lynch (WoodsHole Oceanogr.Inst., WoodsHole, MA 02543} In August1992, a coastalocean tomography experiment was conducted in theBareats Sea over the steep northwestern slope of the BearIsland Trough, about 100 km eastof BearIsland. The oceanographicobjective of the experimentwas to studythe dynamicsof thepolar front and its vicinity using both acoustic tomography and traditional hydrographic techniques. The acoustic objectivewas to studythe effectsof the front and othercoastal oceanography on the acousticpropagation. These objectives are stronglycoupled, in that to effectivelyperform an inversefor the oceanfeatures, one must first obtain a goodunderstanding of the "forwardproblem." In this paper,the effectof the strongfrontal interface is examined,including its corrugations("inter- leaving"features}, internal , and internalwaves on the observedacoustic propagation. Effects on both the modaland ray propagationpictures will be examined,using both theoreticalpredictions and experimentaldata.

2:4•

2pAO5. Spectral integral formalism of wave propagationin a range-dependentwaveguide. Dajun Tang (Woods Hole Oceanogr.last., WoodsHole, MA 02543) and Yue-PingGuo (MIT, Cambridge,MA 02139) This work is the studyof acousticwave propagationin a range-dependentwaveguide, where either the interfacesor the mediumparameters are functionsof horizontaldimensions. For a range-independent,i.e., horizontallystratified, problem where the waveequation can be solvedusing separation of variables,the well-establishedwave-number spectrum formulation has been provedto be a powerfultechnique. When sucha spectrumis known,the modalstructure and its continuouscomponent will completelydetermine the wavebehavior in the waveguide.More importantly,knowledge of the spectralinformation can be used in inversiontechniques to estimateenvironment parameters through acoustic probing. At the ASA Ottawameeting ]Tang and Guo, J. Acoust.Soc. Am. 93, 2284(A} (1993)], Tang and Guo presentedthe spectrumformalism and an applicationof the formalismto an idealwedge. Here the approximatespectral formalism is furtherdeveloped for moregeneral weakly range- dependentproblems. Special attention is paidto the"transition regions" of thewaveguide where the discrete part of thespectrum bordersthe continuouspart of the spectrum.Near suchregions, different parts of the spectruminteract strongly with eachother, resultingin apparentchanges of theacoustic fields. Some examples will bediscussed to elucidatethe advantages of thisapproach.

3.'05-3:15 Break

ContributedPapers

3:15 approximationto that computedwith the "distorted-wave"Born ap- proximation(DWBA). It is shownthat for high sea statesand low 2pAO6. Matched-field 3-D tomographic inversion for geoacoustic grazingangles, distorted waves significantly enhance the backscatterat parameters.A. Tolstoy (Naval Res. Lab., Washington,DC 20375) low frequenciesand consequentlygive better agreementwith experi- Matched-fieldprocessing has recently been applied to the determi- ment. The effectcan be understoodin terms of near-surfaceupward nationof a wide varietyof environmentalparameters. However, nearly refractionthat createsgreater insonification and larger grazingangles all effortshave been directedtoward determiningthose parameters nearthe surface than that obtained with plane waves. Finally, the effect alonga 2-D swaththrough the environment.The approachdeveloped of near-surfaceupward refraction on roughsurface scattering is briefly for the tomographic3-D calculationof deepocean sound-speed profiles discussed. [Tolstoyeta!., J. Acoust.SOc. Am. 1t9, !119-1127 (1991); Tolstoy,$. Acoust.SOc. Am. 91, 781-787 (1992)] has now beenadapted for the determinationof bottom properties,i.e., sedimentthicknesses, sound 3:45 speeds,and densities.The inversiontechnique will be discussedand calculationsin shallowwater environments,where bottom properties 2pAO8, Experimental investigation of features of low-frequency are of paramountimportance, will be presented. broadband acoustical signal propagation in shallow water. V.G. Petnikov, A. R. Kozelsky (Inst. of General Phys., RussianAcad. of Sci. and Ocean Acoust. & Information Ltd., 38 Vavilov St., Moscow, 117942,Russia), and JamesF. Lynch (Woods Hole Oceanogr.Inst., 2pAO7. A higher-order stochastic model for surface backscatter in Woods Hole, MA 02543) highsea states. KennethE. Gilbert and Lucy J. Arecling (Appl. Res. In shallow water, the combinationof downward refractingsound- Lab. andthe GraduateProgram in Acoust.,Penn State Univ., P.O. Box 30, StateCollege, PA 16804) speedprofiles and strongsound absorption by the bottomlimits the range of (tomographic)transmissions and causesone to use lower- A stochasticbubble-layer scattering model based on first-orderper- frequencybroadband signals. In this paper, investigationsof low- turbationtheory (plane-waveBorn approximation)has recentlybeen frequencybroadband (25-95 Hz) acousticsignal propagation in a developed[K. E. Gilbert,submitted to J. Acoust.Soc. Am. (1993)]. in slightly variable shallow waveguidewith a negative water column the first-ordermodel, the scatteringis treatedas a perturbationon the sound-speedgradient are presented.An experimentwas carried out in plane-wavesolution for the bubble-freewater and is writtenin termsof the BarentsSea along a 14-kinstationary track. in travel time tomog- a "geometricfactor" times the horizontalwave-number spectrum of the raphy in shallowwater, as in deepwater, the resolvabilityand identifi- sound:speedfluctuations in the bubblelayer. For low seastates and ability of the acousticarrivals is a necessarycondition. In this experi- highergrazing angles, this approachis adequate.For high seastates and ment, seven stable arrival peaks are noted. Over 2 hr, these peaks low grazingangles, first-order perturbation theory is lessaccurate and fluctuatein rms travel time by severalmilliseconds, which is consistent one needsto accountfor the averagebubble density and computeback- with the measurementaccuracy of the systemused. Identification of the scatterdue to fluctuationsabout the average.In this paper resultsare arrivalsusing both mode theory and rays with beamdisplacement, com- comparedfor scatteringcomputed with the ordinaryplane-wave Born binedwith the ambiguitydiagram approach of Munk and Wunsch,has

1787 d. Acoust. Soc. Am., VoL 94, NO. 3, Pt. 2, Sept. 1993 126th Meeting: AcousticalSociety o! America 1787 shown that some of the arrivals are resolvable modes and some are alsoshown some features associated with phasedislocations passing by. resolvablerays. It was found that the frequencyat which a dislocationoccurs changes slightlybecause of oceanvariability. This frequencycan be considered as a parameterof the acousticfield variability.The resultsof experi- mental observationsof phasedislocations in severalshallow water cw 2pAO9. Exl•erimental observationsof phase dislocationsin shallow and broadbandexperiments are summarized.Discussion of theseexper- water waveguides. A. Yu. Shmelerv,A. A. Migulin (Inst. of General imentswill includesuggestions on the useof the dislocationapproach in Phys., RussianAead. of Sei. and Ocean Acoust. & Information Ltd., 38 tomographicschemes. Vavilov St., Moscow, 117942,Russia), and JamesF. Lynch (Woods Hole Oceanogr.Inst., WoodsHole, MA 02543) 4:1•4:2S Break Previouswork by Petnikov[Akust. Zh. 37, 1212-1215(1991)] and

Shmelervet al. [J. Acoust.Soc. Am. 92, 1003-1007 ( 1992)] hasshown 4:25-$.•0 fastphase fluctuations of up to 180ø in low-frequencycontinuous-wave (cw) signalsmeasured during the CoastalBarents Sea AcousticTest Experiment.These fast fluctuationscan be explainedas phasedisloca- PANEL DISCUSSION: tionspassing through the receivingarray [Kravtsovet al., Soy.Phys. Panel Moderator•' E. C. Shang,J. F. Lynch Acoust.35, 156-159 (1989)]. Recentinvestigations of linearlymodu- Panel Members;' A. Voronovich, D. H. Bernnan,T. F. Gao, J. H. Miller, lated broadbandacoustic signal propagation in the sameregion have C-S. Chiu, D. J. Tang

TUESDAY AFTERNOON, 5 OCTOBER 1993 GOLD ROOM, 1:30 TO 4:10 P.M.

Session 2pEA

Engineering Acoustics:High Power Transducer Materials

Robert Y. Ting, Chair Naval ResearchLaboratory, Underwater Sound Reference Detachment, P.O. Box 568337, Orlando, Florida 32856-8337

Chair•s Introduction•l:30

Invited Papers

1:35

2pEAl. Future directionsin impulsivesound sources. Edward F. Rynne (Naval Command, Control and Ocean Surveillance Ctr., RDT&E Div., 271 Catalina Blvd., San Diego, CA 92152)

While impulsiveacoustic sources have long beenused by the geophysicalcommunity for underwaterexploration, sonar applicationshave been relativelyuncommon. Recent work in the area of electricdischarge devices has led to both a better understandingof the physicsof thisclass of impulsivesound generator and to newdevices, which may in turn leadto an expanded role for such technologyin sonarapplieations•in particular,the observationthat the electricarc commonlyassociated with sparkersound sources represents a wastefuland unnecessarycomplication. Proper electrodedesign and control of the electric dischargecan eliminatethe arc, leavingonly a steambubble, and can therebyenhance the low-frequencyperformance of sucha device.Insight into the performanceand potentialof suchdevices is, in part, a resultof improvedcomputer modeling capabilities of the nonlinearprocesses associated with impulsivedevices, as well as on the useof high-speeddata acquisitionin interpreting experimentalresults. This is especiallytrue for determiningthe effectsof interactionsin arraysof bubblesources. Beyond the electricdischarge sources, understanding of the couplingof energyfrom the bubbleto the soundfield suggests improvements for chemicallydriven sound sources as well. An updateof workon theseimpulsive devices and the modeling efforts that support them is presented.The performanceof somerecently developed devices and the potentialfor futuredevelopment will be discussed.

2:00

2pl•A•. Development of a magneto•trictive sonar transducer using high-temperature supercondueting coils. C.H. Joahi, J.P. Voccio (American SuperconductorCorp., Two TechnologyDr., Westborough,MA 01581), J. F. Lindberg [Naval Undersea WarfareCtr. (NUWC), New London,CT 06320],and A.E. Clark [Naval SurfaceWeapons Ctr. (NSWC), SilverSpring, MD 2o9o31

A low-frequency,dual-piston sonar transducerhas been designed,built, and tested.This transduceruses a terbium- dysprosiummagnetostrictive rod in combinationwith high-temperaturesuperconductive (HTS) coils as the driver element. Terbium-dysprosium,when operatedat cryogenictemperatures, has the highestknown magnetostrictiveconstant. In this transducer,two HTS coils,driven by a combineddc and ac signal,excite the magnetostrictiveelement. The resultantmotion is transmittedthrough the vacuumcryostat enclosing the driver assemblyto two head masses,which transmit the soundto the surroundingenvironment. The combinationof the highmagnetostriction and the absenceof electricaldissipation in the I-ITScoils resultsin very high overallsystem efficiency. Modeling of this type of transducershows overall efficiencies of 80% or more can be obtained.The driverassembly is cooledby a compactStirling Cycle cryocooler. Performance testing in air and watershow

1788 J. Acoust.Soc. Am., Vol. 94, No. 3, Pt. 2, Sept. 1993 126th Meeting:Acoustical Society of America 1788 self-resonanceoccurs at 520and 430 Hz, respectively.The overall system design, as well as measurements of acoustic output and efficiency,will bepresented. [This project was funded by The Naval Undersea Warfare Center, New London, CT, throughthe SmallBusiness Innovative Research (SBIR) Program.]

2:25

2pEA3.Giant electrostrictive response of polymers.Jerry I. Scheinbeim,Brian A. Newman,and ZhenYi Ma (Polymer ElectroprocessingLab., College of Eng.,Rutgers Univ., P.O. Box909, Piscataway, NJ 08855-0909) A newclass of electroacousticmaterials has been discovered at the PolymerElectroprocessing Laboratory, Rutgers Univer- sity,based on theenormous electrnstrictive response available in certainclasses of polymericmaterials. Further, many of the propertiesof thesematerials, including the dielectric constant and elastic modulus, can be tailored for specificend-use applica- tions.The new material is "created" by applying a very large ( > l0 MV/m), debias electric field using a superimposedacdriving signalto producethe required acoustic response. The measured thickness response dr, whichis electrostrictivein nature, is proportionalto the slope of thestrain versus the applied electric field curve and is, therefore, proportional to the applied electric fieldup to saturation. Extremely high dT values (dr> l0 •,/V) canbe accessed at high enough dc bias fields (> 20MV/m).

2:50

2pEA4.Development of electrostrictiveceramic compositions for high-powersonar transducers. Robert Y. Ting (U.S. Naval Res. Lab., UnderwaterSound Reference Detachment, P. O. Box 568337,Orlando, FL 32856-8337) New emphasison activesonar applications requires the developmentof compact,high-power sonar projectors. For low- frequencyuse, one desires to be ableto drivethe transducerelements at highelectric field levels in orderto achievelarge strains. The conventionallead-zirconate-titanatc (PZT) ceramicshave been widely used for the designand fabricationof sonarprojec- tors,but these ceramics suffer the shortcomings of strain limitation and nonlinear properties under high drive. In recentyears, the Navy hasbeen developing new electrostrictivc ceramics of the lead-magnesium-niobatefamily, because these electrnstrictive ceramicscan produce much greater strains than the PZTs.In particular,a newclass of lead-magnesium-niobatelead-titanate (commonlycalled PMN-PT) solidsolution compositions has beenfound to offer the combinedadvantages of high-strain, low-dielectric,and hysteresislosses. The developmentof thesematerials is summarized,and the test resultsfrom prototype transducersfabricated using tbe newelectrnstrictive PMN-PTs are alsopresented. [Work supportedby ONR/T.]

3:15

2pEAS.Materials for thermoaeousti½generation of sound.William C. Ward (LosAlamos Natl. Lab.,MEE-I 3, MS J576,Los Alamos,NM 87545) and ThomasB. Gabrielson (NAWC, Warminster,PA 18974) Thermoacousticgeneration of soundunderwater represents a technology distinctly different from conventional underwater transduction.By properdesign, there is potentialfor high-power,low-frequency generation of continuous-wave,pulsed, or modulatedoutput. From a materialspoint of view,there are three major components: the stack, which maintains the temperature gradientresponsible forpumping the acoustic oscillations; the working medium, which supports the internal acoustic oscillations; andthe heat exchangers, which supply energy from an external source to thestack. Each of thesesubsystems has critical thermal andacoustical requirements that constrain the selection of materialsand the overall source configuration. Thermal conductivity, viscosity,and specific heat replace piezoelectric constants and stress-strain relationships as fundamentalproperties. In addition, theacoustic performance is modeledmore effectively as a waveguidethan as a lumped-parametersystem. Many of theadvantages anddisadvantages of this source technology are readily apparent in thecontext of materialsselection and configuration. [Work supportedby the NavalSpace and WarfareSystems Command, PMW-183.]

ContributedPapers

3:40 3:55

2pEA6. Underwater testing of a thermoaeoustiesound projector. 2pEA7.Electromechanical properties of newelectrostrictive materials Steven C. Black (Naval Res. Lab., Underwater Sound Reference for underwater acoustical applications. Kurt M. Rittenmyer and Detachment, P.O. Box 568337, Orlando, FL 32856-8337 Robert Y. Ting (U.S. Naval Res. Lab., UnderwaterSound Reference Detachment, P.O. Box 568337, Orlando, FL 32856-8337) Electrostrictiveceramics are known to be capableof generating For about the last 10 yr, there has beena growinginterest in the strains that far exceed those of conventional piezoelectric lead- thermoacousticmethod of transduction.Recently, researchhas been zirconatc-titanate (PZT) ceramics.Several lead-magnesium-niobate conductedat Los AlamosNational Laboratory on the developmentof a (PMN) compositionsdeveloped earlier were useful only at highertem- high-power,low-frequency underwater sound projector based on the peraturesthan those of interestto thesonar community. A newbarium- conceptof a thermoacoustieengine [G. W. Swift,J. Acoust.Soc. Am. modifiedPMN-PT ceramicis described.This materialcan operateat 84, 1145 (1988)]. The designof this new transducerconsists of a long lowertemperatures and has very low losses, making it a primecandidate for high-powersonar transducer applications. Another family of elec- straighttube deployed vertically. The upperportion of the tube is gas trostrictivematerials capable of generatinglarge strains is lanthanum- filled and containsthe heat enginedriver. The lower portion is water modifiedPZT (or PLZT). Thesematerials exhibit strains up to 0.1% filled and acts as an impedancematching section. A small-scaledem- alongwith extremelyhigh dielectric strength, but theirhysteresis losses onstration device has been built and was tested both in air and in water. are higherthan thoseof PMN or PMN-PT ceramics.Since the maxi- The demonstrationdevice is approximately9 m in length and operates mum possiblestrain output is usuallythe importantparameter in actu- in the frequencyrange of 100to 200 Hz. In conjunctionwith experi- ator applications,the PLZT familymay have potential for newactuator mentaltesting, modeling of the in-waterbehavior of thisdemonstration designs.Strain measurements for thesenew electrostrictive ceramics at devicewas also performed. Results from the modelingand the in-water highelectric fields but differentfrequency ranges are presented. [Work testingwill bepresented. [Work sponsored by SPAWAR.] supportedby ONR.]

1789 J. Acoust.Soc. Am., Vol. 94, No. 3, Pt. 2, Sept.1993 126thMeeting: Acoustical Society of America 1789 TUESDAY AFTERNOON, 5 OCTOBER 1993 MAJESTIC BALLROOM, 3:45 TO 4:50 P.M.

Session2plD

Tutorials Committee: Hot Topics in Acoustics

Kenneth J. Plotkin, Chair WyleLaboratories, 2001 JeffersonDavis Highway, Suite 70L Arlington, Virginia22202

A specialsession in Hot Topicsin Acousticsis presentedat eachmeeting of the Society.A memberis chosenfrom eachof three or four of the Society'stechnical committees or specialtygroups to presenta tutorialtalk on topicsof currentspecial interest. The talks are intendedto help acousticiansbecome familiar with issuesand achievementsthat are not within their own primary field of interest.

Clmir's Introduction--•:45

Invited Papers

3:50

2pIDl. Hot topicsin psychologicalaenustics. William A. Yost (ParrelyHear. Inst., LoyolaUniv. of Chicago,6525 N. Sheridan Rd., Chicago,IL 60201)

Psychologicalacoustics, or ,is the study of therelation between sound and the behaviorof humansand other animals.Such relations are usuallyreferred to as "hearing."In recentyears, the psychoacousticalstudy of heatinghas returned to a major question,"How doesan organismdetermine the sourcesof soundin its environment,especially when there are a numberof simultaneouslyprescnt•l soundsources?" The sensoryreceptors for hearingare sensitiveto the physicalproperties of the soundfield impingingon the organismand are not selectivefor processingsound sources. The brain mustprocess the neural codeof the incomingsound field in order for the organismto determinethe sourcesof the soundthat make up the input sound field.The neuralcode for soundprovided by the auditoryperipheral nervous system is a temporal-spectralrepresentation of the total soundfield. This talk will highlightrecent developments in simulatingthe temporal-spectralcode provided by the auditory peripheryand advancesin the studyof propertiesof thiscode that mightbe usedby the brainto aid the organismin determining the sourcesof sounds.[Work supportedby NIDCD and AFOSR-Life Sciences.]

4:10

2plD2. Hot topicsin physicalacoustics. Lawrence A. Crum (Appl. Phys. Lab., 1013 NE 40th Street,Univ. of Washington, Seattle, WA 98105}

Becauseof the technicalarea of physicalacoustics represents the centerof Lindsay'sWheel of Acoustics,this area is oftenthe originof manyresearch topics that eventuallyfind application in othercommittees, and even other disciplines. Thus, "hot" topics in physicalacoustics can be definedas anythingdone by physicalacousticians, especially if they involvebubbles! However, for the benefitof thosefrom outsidethis area who want to learn somethingabout this excitingcommittee, a numberof topicsthat are currentlyof majorinterest will bediscussed briefly and a few sdectedtopics of particularinterest to the presenterwill be discussed in moredetail. In particular,it will be shownhow a few specifictopics being developed by physicalacousticians have direct relevanceto problemsof moregeneral interest to our society.For example,advances in the importantnew area of sonochemistry await progressin the fundamentalunderstanding of sonoluminescence;advances in the newventures of medicalultrasound, such as extracorporealshock wave lithotripsy and ultrasonicsurgery, await a morecomplete understanding of acousticcavitation and nonlinearacoustics; the utilizationof containerlessprocessing of exoticmaterials in spaceawaits developmentsin acoustic levitationand an understandingof the surface-oscillationcharacteristics of liquid drops.These and similartopics will be discussed in some detail.

4'30

2plD3. Hot topicsin noise:Sound quality of products.Richard G. Cann (RH Lyon Corp, Cambridge,MA 02138)

The qualityof a soundthat a productmakes is usedby the listenerin manyways. Broadly, the listenerjudges from the sound qualitythe identificationof the typeof the source.Once identified, the informationcontained in the soundmay be usedfurther. It maybe usedfor practicaldiagnostic purposes, such as identifyingan unanticipatedfault or a modeof operation.It mayalso be usedon an aestheticlevel to qualifythe acceptanceof the product.So, in manyways what one hears is usedsimilarly to what one smellsor eventastes. Over the years,researchers in psychoacousticshave developed many mettles for soundquality. However,the primaryfocus has beentoward one end of the sound-qualityacceptance spectrum--those sounds that annoyor irritate rather than thosesounds that gain acceptanceor please.The applicationof sound-qualitytechniques implies that well-definedspecifications for the soundquality must be writtenso that a manufactureris clearlyable to acceptor rejecta product.This requirementwill be evenmore acute in the futurewhen many more products will be designedon onecontinent, built on another, and used on a third.

1790 J. Acoust.Soc. Am.,Vol. 94, No. 3, Pt. 2, Sept. 1993 126thMeeting: Acoustical Society of America 1790 TUESDAY AFTERNOON, 5 OCTOBER 1993 VAIL ROOM, 1:00 TO 3:40 P.M.

Session2pNS

Noise and Psychologicaland PhysiologicalAcoustics: Current Research in Hearing Protection Device Testing

Elliott H. Berger,Chair CabotSafety Corporation, 7911 Zionsville Road, Indianapolis, Indiana 46268-1657

Invited Papers

1:00

2pNS1.Development of a newhearing protector test standard---Overviewof the effortsof ANSI S12/WGll. Elliott H. Berger (CabotSafety Corp., 7911 Zionsville Rd., Indianapolis,IN 46268-1657) In 1987,ANSI SI2/WGII (previouslydesignated S12-26) was given an expandedscope and a newtitle, namely, FieM Effectivenessand Physical Characteristics of Hearing Protectorg The WG wasdirected to explorethe problems inherent in using optimum-performancelaboratory-derived real-ear attenuation data to estimateachievable and/or typical workplace protection, andto identifyor developprocedures that could yield improved estimates of fieldperformance. After careful deliberation, the WG determinedthat a new laboratory-basedreal-ear attenuation at thresholdprocedure with explicitlydefined subject selection, trainingsupervision, and fitting techniques could potentially provide useful estimates of obtainablefield performance. The WG deviseda draft protocoland subjectedit to a pilotstudy [Berger et al., J. Acoust.Soc. Am. Suppl.1 88, SI0 (1990)]. Subsequently,the protocolwas modified and utilized in a full-scaletest of threetypes of earplugsand one earmuff, by four independentlaboratories. The testing was conducted from September 1990 through December 1991. This presentation begins with an overviewof thehearing protection rating problem and the rationale for theactivities of WGI 1, aswell as an introductionto the remaininginvited papers in thesession, which focus on the needsfor improvedhearing protector attenuation data and the resultsof the interlaboratory study.

1:25

2pNS2.Why users need accurate real-world estimates of hearingprotector's ratings. C. Dixon-Ernst(Occupational Health Program,Alcoa, 1501 Alcoa Bldg., Pittsburgh, PA 15219)and A. Behar (OntarioHydro, Whitby, ON LIN 9E3,Canada) Accuratevalues for hearingprotectors' attenuations are needed by occupationalhealth professionals who deal with hearing conservationof employees exposed to noiselevels in excessof 85 dBA.The problembecomes yet moreimportant in large corporationswith extensive use of those devices. Inaccurate NRR valuesmay be the cause of increases in hearing losses, worker's compensationclaims, and liabilities. Overestimation ofthe NRR mayresult in a decreasein the use of engineering noise controls. Eachof theseareas will be highlightedand explained.

1:40

2pNS3.Results of the S12 WorkingGroup 11 interlaboratorystudy to approximatereal-world attenuation of hearing protectiondevices (HPDs). JuliaD. Royster (EnvironmentalNoise Consultants, Inc., P.O. Box 30698, Raleigh, NC 27622) and Larry H. Royster (North CarolinaState Univ., Raleigh,NC 27607) FourHPDs, three plugs and one muff, were tested in fourlabs to identifya protocolthat would estimate the real-world attenuationobtained in fieldstudies of workersin hearingconservation programs. Audiometrically experienced subjects who had neverworn HPDs regularly used each device, following the manufacturers' instructions without any supplemental experimenter training(subject-fit condition). Subsequently, after the experimenter demonstrated theuse of each device, the subject used each HPDagain (informed-user-fit condition). Attenuation was measured intwo trials with each HPD in each instruction condition. Practicewithin a conditionyielded no significantimprovement in achievedattenuation. Experimenter instruction significantly increasedthe attenuation subjects obtained with earplugs (but notearmuffs). The subject-fit condition approximated the upper quartileof real-worldattenuation, and the range of standarddeviations of attenuation across labs was no greater than for the informed-user-fitcondition, indicating acceptable reproducibility. Testing earmuffs worn with safetyglasses only slightly in- creasedthe rangeof standarddeviations.

2:05

2pNS4.Hearing protector attenuation from subject-fit methods at the worksite and in the laboratory.John R. Franks (Bioacoust.and Occupational Vibration Section, Natl. Inst.for OccupationalSafety and Health, 4676 Columbia Pkwy., Mail StopC-27, Cincinnati, OH 45226-1998)and JohnCJ. Caaall (VirginiaPolytechnic Inst., Blackaburg, VA 24061} A disparityexists between the advertised and realized attenuation of noise by hearing protective devices. The disparity has beenaccredited to manyfactors, including overfitting by experimenters and misuse by workers. This study compared attenuation datafor three earplugs and one earmuff obtained from an interlaboratory (IL) studyusing a subject-fitmethod with data on the sameprotectors reported in theliterature from work-site (WS) studieswhere workers fitted the hearing protection and with

1791 J. Acoust.Soc. Am., Vol. 94, No. 3, Pt. 2, Sept.1993 126thMeeting: Acoustical Society of America 1791 manufacturer-reported(MR) dataon NRR labels.The IL methodrequired subjects who where audiometrically competent, but inexperiencedwith hearingprotectors, to fit hearingprotectors relying solelyupon guidancefrom the manufacturers'written instructions.Results indicated that therewere no differencesin attenuationsbetween laboratories. Confidence interval testing was performedcomparing the IL mean attenuationsand variancesto WS meansand standarddeviations and to MR meansand standard deviations. Results indicated that the IL data were more consistent with the WS data than with the MR data. In all cases the IL data weresignificantly less than the MR data. Dependingupon protector type, the IL data wereequivalent to or greater than the WS data.

2:30

2pNS5. Samplesize necessaryto provideacceptable reproducibility in laboratoryhearing protector attenuation testing. John R. l•ranksand Carol J. Merry (Bioaconst.andOccupational Vibration Section, Natl. Inst. for Occupational Safety and Health, 4676 ColumbiaPkwy., Mail Stop C-27, Cincinnati,OH 45226-1998}

The ANSI standardmethoff for determiningreal-ear attenuation at thresholdrequires that no lessthan ten subjectsbe used and that eachsubject be testedno lessthan threetimes each with earsoccluded and with earsopen. Attenuation is calculatedas the differencebetween each paired open and occludedthreshold. The grandmean attenuation is calculatedfor all 30 attenuations. The standarddeviation calculation is basedon the differencebetween each attenuation and the grand mean.The ISO standard requiresno lessthan 16 subjectswith no lessthan one calculationof attenuation.From an interlaboratorystudy usingthe subject-fitmethod, it was possibleto evaluatethe numberof subjectsand numberof repeatedmeasures per subjectnecessary to reacha desiredconfidence interval and levelof accuracy.The resultsindicated that the numbervaries with the type of hearing protectorand centerfrequency of the testingnoise. To reach4-3 dB for an earmuff,as few as I 1 subjectswith one attenuation test per subjectwas adequate, while for one of the earplugsmore than 75 subjectswith two attenuationtests per subjectwere necessary.Implications of theseresults on laboratorytesting strategies will be discussed.

2:50

2pNS6. Comparisonof WGI1 study variability to that of other interlaboratorystudies. Charles W. Nixon (Armstrong Lab., Crew SystemsDirectorate, 2610 SeventhSt., Wright-PattersonAFB, OH 45433-7901} The variabilityof the data measuredin the W(311 interlaboratorystudy was comparedwith that measuredin three other interlaboratorystudies conducted in this country,in Europe,and in the Scandinaviannations. All studiesutilized a real-ear attenuationat the thresholdmeasurement paradigm and basicallyfollowed the proceduresdescribed in the currentANSI and ISO hearingprotector measurement standards, with one major exception.The W(311 study utilized naive subjectsand hearing protectorfitting procedures that wererelatively free from experimenterinfluences instead of the trainedsubjects and the "bestfit" proceduresrequired by currentmeasurement standards. A subjectfit (onlyhearing protector manufacturer's printed instructions handedto the naivesubjects} and an informeduser fit (manufacturer'sinstructions plus experimenter general comments to the naivesubjects only relativeto the instructions}were utilized for the WGI I studymeasurements. Comparisons indicate that the variabilityof the data collectedunder the lessrigorous subject and fitting proceduresof the W(3 11 studyis at leastequivalent to that measuredin the other interlaboratory studies.

3:10

2pNS'/. A discussionof WGII's anthropometricdata with comparisonto other availabledatabases. Doug Ohlin (U.S. Army EnvironmentalHygiene Agency, Bio-Acoust- Div., AberdeenProving (3round, MD 21010-5422)

Anthropometri½and demographicdata were compliedfrom four participatinglaboratories on subjectsused in W(311's round-robintesting. Age and sex distributionswere comparedto sizingdistributions of the single-flange(V-SiR) and EP-100 earplugs.Earplug size was generally found to increasewith age,while females were found to be skewedtoward the smallersizes andmales toward the largersizes. Measurements of ear length,ear breadth, pinna protusion, and head height were compared to military standardsfor anthropometricdata.

ContributedPaper

3-.25 mountedin the baseplate. A 20-cm-diamaluminum tube, 20 cm in length,is attachedby annularflanges to the baseplate at oneend and, 2pNSS. Measuring the performanceof circumaural hearing protectors and communicationhead setsat low frequencies. J. (3. Ryan, E. A. at the other, to a 15-cm-diamloudspeaker, which drivesthe enclosed (3. Shaw, A. J. Brammer, and (3. Zhang (Inst. for Microstructural volume so formed. The excitation of cross modes within the tube is S•icncca, Natl. Res. Council, Oltawa, ON KIA OR6, Canada) auppr•aacdby a 2.0-cm cylindrical annular layer of felt, in contact with the inner wall of the tube.The performanceof the measuringsystem An enclosurehas beenconstructed to evaluatethe performanceof will be describedand resultsreported for the attenuationof an analog activenoise reduction (ANR}, circumauralhead sets, and hearingpro- ANR head set. [Work done in collaborationwith the Defenceand Civil tectors,at frequenciesbelow 800 Hz. It consistsof a massive(5-kg}, fiat baseplate againstwhich one cup cushionis sealedby springpressure. Institute of Environmental Medicine.] The sound pressurewithin the cup is recordedby a microphoneflush-

1792 J. Acoust.Soc. Am., VoL 94, No. 3, Pt. 2, Sept. 1993 126thMeeting: Acoustical Society of America 1792 TUESDAY AFTERNOON, 5 OCTOBER 1993 SILVER ROOM, 1:00 TO 3:45 P.M.

Session2pPA

PhysicalAcoustics: Bubbles and Other Topics

Wayne M. Wright, Chair PhysicsDepartment, Kalamazoo College, Kalamazoo, Michigan 49006

ContributedPapers

1:0O perimentaldata for high-power,high-frequency waves in argonat high pressure. 2pPA1. Capillary wave turbulence. William Wright, Raffi Budak, and SethJ. Putterman (Phys.Dept., Univ. of California,Los Angeles, CA 90O24) 1:45 The transitionfrom a discretespectrum of higherharmonics to a 2pPA4. A new explanationfor the double resonanceof a pure vapor broadbandpower spectrumhas been observedwith a wire probe (as bubble. Yi Mao (Dept. of Phys. and Astron., Univ. of Mississippi, regardsthe frequencyspectrum) and imagingof the surface(as regards the wave-numberspectrum). By useof laserscattering techniques we University, MS 38677), Lawrence A. Crum, and Ronald A. Roy hopeto obtainan absolutecalibration of the surfacemotion in this very (Univ. of Washington,Seattle, WA 98105) far-offequilibrium state. [Work supportedby the U.S. DOE Divisionof Engineeringand Geophysicsand by NASA.] Thesecond resonance frequency fo(2) of a purebubble appeared first in R. D. Finchand E. A. Nippiras'theoretical analysis [J. Acoust.Soc. Am. 53, 1402-1410 ( 1973)]. However,no one hasbeen able to observe 1:15 a vaporbubble oscillating at f•02). A newanalysis based on numerical calculationsshows that .f(o 2) isphysically unstable. By analogizing bub- 2pPA2. Absorptionof finite-amplitudeultrasound in biomedical ble oscillationswith thoseof a mass-springsystem, it is foundthat the tissue. Ping-Wah Li and David T. Blackstock (Appl. Res. Labs., resonancefrequency F(fa) dependson the drivingfrequency fa and Univ. of Texas, Austin, TX 78713-8029) thereal bubble resonance fro2) is a solutionof F(fd) =fd. Thebehavior A theoreticalinvestigation of the absorptionof finite-amplitudeul- of F(fa) nearfa=f? showsthat the bubble tends to shiftits oscilla- trasoundin biomedicaltissue is reported.The tissueis modeledas a tion frequencyaway from fo •2) (repulsive);whereas F(fa) nearthe medium having multiple relaxation processes.A generalizedBurgers ordinaryresonance fo•t) isattractive. A theorydeveloped by the authors equation,which includes the effectsof nonlinearityand relaxation,is for directlycalculating the resonancefrequency and the dampingcon- derived.Analytical and numericalsolutions of this equationfor a step stantwithout using the mass-spring analogy gives only f?. Therefore, shock,a periodicwave, and a temporalGaussian pulse are presented. we are forcedto the conclusionthat f?) resultsfrom an improper The resultsare usedto calculatethe finite-amplitudeabsorption coeffi- mass-springanalogy and is notphysically observable. [Work supported cientand temperaturerise in the tissue.It is foundthat nonlineardis- by ONR.] tortioncauses the absorptionand the temperaturerise to be significantly higherthan that for small-signalultrasound. [Work supported by NIH, ONR, and ARL:UT IR&D.] 2:00

2pPA5. Vapor bubblesrevisited. RobertD. Finch (Dept. of Mech. 1:30 Eng., Univ. of Houston,Houston, TX 77204-4792)

2pPA3. High-frequency(10-25-MHz) wavepropagation in argonat Mao et al. [J. Acoust.Soc. Am. 93, 2379 (1993)] have revived pressuresup to 10 MPn, C-H. Chiangand L. J. Bond (Ctr. for interestin the subjectof the dynamicsof vaporbubbles, including the Acoust., Mech. and Mater., Univ. of Colorado, Campus Box 427, issueof "double"resonances. Some earlier work on this topic will be Boulder, CO 80309-0427) summarized,and a possibleapplication will be discussed. Acousticwave propagation in gaseousargon has been investigated usinga high-powerultrasonic gated-tone-burst transmission system. Re- sultsof measurementsof compressionwave absorption and velocityin 2:15 argonat frequencies10 to 25 MHz, at staticpressures up to 10 MPa, at temperaturesof 21 to 23 øC,and at highpower (above critical intensity 2pPA6. Rectified diffusion and single-bubble sonoluminescence. 16.97 W/m 2 at 10 MHz and 10 MPa) are presented.For small- Ritva Lofstedt, Bradley P. Barber, and Seth Putterman (Phys. Dept., amplitudewaves at pressuresup to 2 MPa, the resultingdata are in Univ. of California, Los Angeles,CA 90024) goodagreement with that predictedusing ideal gas equations and fun- damentalthermophysical gas constants. At staticpressures higher than The remarkablylow solubilityof air in water may be essentialto the 4 MPa and for higher-powersettings, distortion of the waveformis observationof stablesingle-bubble sonoluminescence (SL) in this sys- observed.Excess attenuation, in additionto classicalabsorption, is also tem.In otherliquids, the massexchange during a singlecycle appears to foundat higherpower settings. With a 10-MHzfundamental frequency, be sufficientto quenchsingle-bubble SL. To gaininsight into thisissue, significantsecond harmonic generation is observed.The data arc com- ( I ) a theory is developedthat unifiesmass diffusion and the Rayleigh- paredwith existing theories for finite-amplitudewaves in fluids.Current Plessetequation, and (2) laserscattering is usedas a probeof thetime theories[F. Dunn et al., IEEE Ultrason.Syrup., 527-532 ( 1981); A. L. changeof bubbleparameters due to massdiffusion. [Work supported by Thuras et al., J. Acoust.Soc. Am. 6, 173-180 (1935)] for harmonic the U.S. DOE Divisionof AdvancedEnergy Projectsand Divisionof generationand attenuationare shownnot to predictthe observedex- Engineeringand Geophysics(Theory); R. L. is an AT&T fellow.]

1793 J. Acoust.Soc. Am., Vol. 94, No. 3, Pt. 2, Sept. 1993 126th Meeting:Acoustical Society of America 1793 2'.30 old is 2.0, whichis in the upperrange of diagnosticultrasound. The resultsalso show that the cavitationdepends strongly on the sizeof the 2pPA7. Mode-locked sono]lumin•ceocein a seAtledsystem. Robot polystyreneparticles added in the water. [Work supportedby NIH Hiller and Bradley P. Barber (Phys. Dept., Univ. of California, Los through (}rant No. R01 CA39374.] Angeles,CA 90024)

The meanswhereby synchronoussingle-bubble sonoluminescence 3:15 can be achievedin a scaledsystem will be discussed.This techniqueis 2pPAI0. Effect of microbubbleson self-slmilar waterborne shocks. importantfor the studyof gasesand liquidsother than air and water B. Edward McDonald (Naval Res. Lab., Washington,DC 20375) and also to maintain a constantpartial pressureduring an extended experimentalrun. For temporalstability, sonoluminescence and an os- Similarity solutionsdeveloped from the equationsof nonlinear cillatorcan be mode-locked.Also the sonoluminescencingresonator can acoustics[P. H. Rogers,J. Acoust.Soc. Am. 62, 1412-1419(1977); B. be mode-locked to itself. Measurements that make use of these tech- E. McDonald and J. Ambrosiano, J. Acoust. Soc. Am. 84, 1497-1503 niqueswill be presented.[Work supportedby the U.S. DOE Divisionof (1988)] haveadequately accounted for the rangedependence of over- AdvancedEnergy Projccts.] pressuresin the propagationof underwaterspherical shocks, while giv- ingonly fair to poorpredictions for relaxationtime constants at large 2.•5 rangesfrom the source.The relaxationtime discrepancyscems to sug- gest an anomalouslylarge nonlincarity coefficientat great distances 2pPA8. Commentson the effect of an acousticfield on the shape from the source.The effectof minute quantitiesof entrainedair on the oscillationsof levirated drops and bubbles. Thomas J. Asaki and shocksimilarity solution for water is investigated.It is well knownthat Philip L. Marston (Phys.Dept., WashingtonState Univ., Pullman, microbubblescan greatlyincrease the nonlinearitycoefficient of waterat WA 99164-2814) ambientconditions. At high ,however, bubbles may collapse to the pointof beingdynamically unimportant. The equationof statefor Acousticlevitation has been usedas a methodfor measuringthe wateris modifiedto accountfor ambientmicrobubble populations, and frequencyand dissipative properties of shapeoscillation modes of drops the resultingequations solved for self-similarshock profiles. Using air and bubbles[P. L. Marstonand R. E. Apfel, J. Acoust.Soc. Am. 67, voidfraction as a fit parameter,observed relaxation time dataare ana- 27-37 (1980); T. J. Asaki et at, J. Acoust. Soc. Am. 93, 706-713 lyzed to yield the levelsof entrainedair that may havebeen present in ( 1993)]. One of the problemsin the interpretationof such measure- variousunderwater explosive experiments. mentsis the effectof the leviratingfield. Some of the relevantissues for slightlydeformed drops or bubbles,where the equilibriumshape is sphe- 3:30 roidal and R is the radiusof the sphereof the samevolume, are exam- ined. The interactionof shapeoscillations with the external acoustic 2pPAI1. An electrical-discharge, steam-bubble aennstic flowis approximatedfor a spheroidat the velocityantinode of a stand- source•thenry and experiment. Allen H. Olson and Stephen P. ing wavein the long-wavelengthlimit (kR-,O) with the resultthat the Sutton (Naval Command, Control and Ocean Surveillance Ctr., effectiverestoring for the quadrupolemode is increased.The cur- RDT&E Div., Code 711, 271 Catalina Blvd., San Diego, CA vatureof the effectivepotential well is increased.The analysismakes use 92152-5000) of the known solutionfor the potentialflow past an incompressible spheroidin the kR•O limit. [Work supportedby ONR.] Electricalenergy stored in a high-voltagecapacitor bank is rapidly discharged into seawater. Smooth spherical electrodesare used to achievenearly uniform heatingof the seawaterin the inner-electrode 3.•0 gap.This allowsthe water to be superheated,in the liquid state,without 2pPA9. Detection and generation of transient aenustic electricalbreakdown. As the high-pressure,high-temperature liquid ex- microcavitafionat 4.3-MHz center frequency. Qihong Xu, Xiaoyu pandsagainst the surroundinghydrostatic load, the phasetransition to Zheng,and Robert E. Apfei (Ctr. for Ultrasoniesand Sonies, P.O. Box steamoccurs. The rapid volumegrowth of the steambubble then gives 2159, Yale Station, Yale Univ., New Haven, CT 06520) riseto a very broadband,high-frequency acoustic pulse. Experimental dataare presentedfor 1.9-em-diamelectrodes separated by 1.0cm in 20 To studythe potentialbioeffects caused by applicationsof medical f• cm seawater. The electrical resistance is shown to be a function of the diagnosticultrasound, a highly focusedtransducer with centerfre- energydelivered to the water. A fully three-dimensionalconduction quencyat 4.3 MHz was usedto generatemierocavitation in water modelis presentedthat takesthe electrodegeometry and knownphys- seededwith polystyreneparticles, and the cavitationwas detected by a ical propertiesof seawateras input. The computationproceeds in con- modifiedactive detection system JR. A. Roy et aL, J. Acoust.Soc. Am. stantenergy steps, with spatialvariation in temperature,electrical con- 87, 2451-2458 ( 1990}]. The resultsshow that the cavitationthreshold is ductivity, and electricpotential updated at the end of each step.The about 4.0 MPa in water seededwith polystyreneparticles of 0.1 pm modelaccurately predicts the observedelectrical resistance and the on- diameter.The mechanicalindex corresponding to the cavitationthresh- set of steam formation.

1794 J. Acoust.Soc. Am., Vol. 94, No. 3, Pt. 2, Sept. 1993 126th Meeting:Acoustical Socieb/of America 1794 TUESDAY AFTERNOON, 5 OCTOBER 1993 CENTURY-SPRUCEROOM, 1:25TO 4:45 P.M.

Session2pSA

Structural Acoustics and Vibration: Characterization of Viscoelastie Materials II

Wayne T. Reader, Cochair VectorResearch Company, Inc., 2101 EastJefferson Street, Rockville, Maryland 20852

Bruce Hartmann, Cochair NavalSurface Warfare Center, 10901 New HampshireAvenue, Silver Spring, Maryland 20903-5000

Chair's Introduction--l:25

Invited Papers

1:30

2pSAI. An overviewof fractional-ordercalculus applied to viscoelasticity.Ronald L. BagIcy (StructuresDiv., Wright Lab., Wright-PattersonAFB, OH 45433) Overthe past 80 yr, an initiallyobscure branch of calculushas gained some attention as a compact,mathematically convenient descriptionof linearviscoelasticity. Rieman and Liouville developed the classical definitions of fractional-orderintegration and differentiation.These definitions are fading-memory,linear operators well-suited for describingrelaxation, dispersion, and atten- uationeffects. Early in this century,several authors suggested ad hocfractional-order differentials to describeviscoelastic effects. ScottBlair firstsuggested the Riemanand Liouville operators in theearly 1940s. Several investigators have subsequently echoed ScottBlair's suggestion. More recently,the fractional-ordercalculus viscoelasticity formulation has been expanded to include dynamicsand finite-element formulations. Most recently, the formulation has led to thedevelopment of the thermorheologically complexmodel, a generalizationof the thermorheologically simple material model, and the model has been related to molecular bondenergy decay and fractals.Other recentlydeveloped engineering applications of fractionalcalculus include corrosion, aeroelasticity,and feedbackcontrol.

2:00

2pSA2.A newshift factor for thecharacterization of the dynamic properties of viscoelasticmaterials. Ahid D. Nashif ( Roush Anatrol, Inc., 10895 Indeco Dr., Cincinnati, OH 45241) Duringthe courseof characterizingthe dynamicproperties of a varietyof viscoelasticmaterials, over the last 10 yr, the Arrheniusequation was found to bevalid for describingthe shift factor over the glassy, transition, and rubbery regions of the material.Based on this observation,the work describedwas initiated to definethe activationtemperature in termsof the dynamic behaviorof viscoelasticmaterials. It will beshown, both empirically and analytically, that the activationtemperature is a unique functionof thedynamic behavior of viscoelasticmaterials, which can be accurately determined once the properties of thematerial havebeen measured for anyfrequency but over a widetemperature range. Two advantages exist for usingthis unique expression to describethe shift factorinstead of the previouslyused ones. The firstis that it eliminatesthe cumbersomeand sometimes questionableways of curve-fittingthe data. The second, which is more important, is thatby using this unique function to reduce thedata results in a smoothset of pointswithout discontinuities; otherwise, the measured data are questionable, and their validity should be investigated.

2:30

2pSA3.Standard viscoelastic material. R.E. Wetton,J. C. Duncan,and G. M. Foster (PolymerLabs. Ltd., The Technology Ctr., EpinalWay, LoughboroughLEI 1 0QE, UK) Whereasthe moduli of elasticsolids and the viscositiesof simplemolecular liquids are well-defined,such that many can bc usedas standards,the sameis not true of viscoelasticmaterials. The propertiesof the latter are by definitionboth frequencyand temperaturedependent. In thispaper some candidate materials and the results obtained over a wide(-100 to +100øC) temperaturerange and a fairlywide measurement frequency range (0.01-100 Hz) are considered.In orderto extendthis frequencyrange, particularly into the kHz range,the time-temperature superposition ideas of Williams,Landel, and Ferry are

1795 J. Acoust.Soc. Am., Vol. 94, No. 3, Pt. 2, Sept. 1993 126th Meeting:Acoustical Society of America 1795 used.This necessitatesthe materialconforming to this treatmentby virtueof possessinga temperature-independent relaxation spectrum,to a goodapproximation. In order to haverelatively high damping at ambient,the polymer has to havea Tgaround 0 øC,and, to be thermorheologicallysimple, it hasto be predominantlysingle phase. The bestcandidate materials have been found to be random copolymersof butadieneand acrylonitrile.

Contributed Papers

3.•0 Kelvin-Voigt model,guided by a scalarexpression, matched experimen- tal attenuationover the limitedtransducer frequency band and provided 2pSA4. Characterizationof candidatestandard polymers. Wayne T. a viscoelasticdamping coefficient,which is a measureof viscosity.Ul- Reader,N. ScottEmery, and Lois S. Pena (Vector Res.Co., Inc., 2101 trasonicnondestructive evaluation was usedon a sampleof inert pro- E. JeffersonSt., Ste. 700, Rockville, MD 20852) pellantat the 51hand 1lth monthsafter casting.A matchedpair of 50 Investigatorsactively engaged in the measurementof themoduli and kHz transducers,wavelength in the material of 3.2 cm, were usedin 120 lossfactors of viscoelasticpolymers are well awareof the diversityof tests.The preliminaryexperimental results indicate a decreasingatten- resultsobtained by differentmeasurement techniques---even though the uationand associatedviscoelastic damping coefficienl as time increases. specimensare fabricatedto be identical.To alleviatethis perennial prob- Further testingwill be usedto ascertainan empiricalrelationship be- lem, the ASA hassponsored working group S2WG79 to identifyseveral tweenattenuation, viscoelastie damping coefficient, and Young'smod- polymersfor use in calibrationof the multitude of apparatusesbeing ulus over time, and their relationshipto the safelife for motors. usedto characterizedynamic toodull and lossfactors. Criteria usedto selectcandidate polymers include ready availability, property stability, 3:45 bondabilityto mountingblocks, versatility to eoverwide frequency and temperatureranges, manufacturing repeatability, and, mostimportant, 2pSA7. An optimized finite-difference scheme for high-loss rheologlcalsimplicity. Three candidatepolymers have beenproposed viscoelasticmaterials. Mark A. Hayher and J. Robert Fricke (Dept. and distributed for initial evaluation. Evaluations of how these candi- of Ocean Eng., Rm. 5-218, 77 MassachusettsAve., Cambridge, MA datesperformed on a PolymerLaboratories DMTA will bc presented, 02139) and their suitabilityfor standardmaterials as determinedby the selec- tion criteria will be addressed. In an effort to attenuatehelical wave energyin cylindricalshells and reduceits couplingto the surroundingfluid, variousconstrained layer shell designsare being investigated.The shell skins being considered 3:15 have an effectiveloss factor •t of order unity. As part of this effort, an efficienttime-domain finite-difference scheme is being developedwith 2pSAS. Efficiency of viscoelasticmaterials in the vibration reduction the ultimateobjective of constructing3-D modelsof suchshells. Opti- of thin rectangularplates. R. Lapointeand L. Cheng (Mech. Eng. mizationof relaxationtime spectrafor !ow-•/materials,done by Blanch Dept., Universit6Laval, QurbecGIK 7P4, Canada) et al. [TechnicalReport, Rice University,Dept. of Geologyand Geo- The problemof reducingstructural vibration with viscoelasficma- phys. (1993}], is extendedto high ;/by matchingboth the real and terialswhile addingthe leastextra weightpossible has always been of imaginaryparts of the complexmodulus with experimentaldata. To greatinterest, especially in the aeronauticfield. To studythis, the sys- improvescheme accuracy further, the matchingis done again after tem consistingof a thin rectangularplate coveredby (uneonstrained) diseretizationto minimizethe effectsof numericaldispersion and dissi- sectionsof viscoelasticmaterial that are also rectangularwill be used. pation. Data has been matchedfor a material with •/=0.5 over one The minimizationof the vibrationlevel of the plate when subjectto frequencyoctave using a Crank-Nicholson schemewith two relaxation external forces using a determined of coveragewill then be times.The generalapplicability, accuracy, and efficiency of thisnumer- treated,with specialattention given to the frequency-and temperature- ical optimizationprocess are subjectsof continuingresearch. Compar- dependentcharacteristics of the viscoelasticmaterials. The mathemati- isonbetween numerical simulation and analyticalsolutions are givenfor cal modelof the systemis first developedfollowing the Love-Kirehoff wavepropagation in a constrainedlayer fiat plate. [Work supportedby plate theory and a polynomial Rayleigh-Ritz approximation. The ONR.] searchfor the minimallevel, using the simulatedannealing technique, is

then initiated.Numerical results will be presentedand opportunitiesfor 4:00 usingthese results for more complexsystems will be discussed.

"ROUND TABLE" DISCUSSION: Moderators:Wayne T. Reader and Bruce Hartmann 2pSA6. Measurement of changes in the bulk material properties of solid rocket motor propellant. Rosario Nici (Dept. of Astronautics, The objectiveof this "Round Table" discussionperiod is to involve USAF Aead., Colo?adoSprings, CO 80840) and Leonard J. Bond the speakersand the audiencesof the two sessions"Characterization of (Univ. of Colorado, Boulder, CO 80309-0427) viscoelasticmaterials I and If" in an opendiscussion of topicsimportant to researchersconcerned with the characterizationand applicationsof Solidrocket motor propellant's bulk viscoelasticmaterial properties viscoelasticmaterials. Suggested discussion topics include, but are cer- changewith ageand service history. Safety considerations preclude the tainly not limited to: measurementtechniques and apparatuses,crite- useof propellantafter an estimatedservice life. An ultrasonicmethod rion for the selectionof standardpolymers, time/temperature shift al- that characterizesthe materialby trackingattenuation and velocity,as gorithms,determination of static toodull, ideotifieationof new research a functionof frequency,over time is presented.No record of service areas,and clarificationof issuesraised in paperspresented during the history was assumed.A simple numerical simulation,based on the two sessions.

1796 J. Acoust.Soc. Am.,VoL 94, No. 3, Pt. 2, Sept. 1993 126thMeeting: Acoustical Society of America 1796 TUESDAY AFTERNOON, 5 OCTOBER 1993 MAJESTIC BALLROOM, 1:00 TO 3:30 P.M.

Session2pSP

SpeechCommunication: Topics in SpeechRecognition

loan Bachenko, Chair .4T&T Bell Laboratories,600 Mountain•1oenue, Murray Hill, NewJersey 07974

ContributedPapers

1:00 Eng., Univ. of Waterloo, Waterloo, ON N2L 3GI, Canada) 2pSPI. Use of explicit duration models in speechrecognition. CynthiaFong and Mari Ostendorf (ECS Dept., BostonUniv., 44 The formulation of the hidden Markov model (HMM) has been CummingtonSt., Boston,MA 02215) successfullyused in automaticspeech recognition for almosttwo de- cades. In the standard formulation, the individual statesin the HMM Althoughresearchers have observed that automaticspeech recogni- are eachassociated with a generallydistinct but stationarystochastic tionerrors are often associated with improbableduration patterns, cur- process.This makes the standard HMM inadequatefor representingthe rent recognitionsystems take little advantageof knowndurationai cues. nonstationaryproperty of the many speechsegments intended to be In additionto usingsimplistic models of duration,recognizers put very describedby the HMM-state statistics.A generalizedHMM has been little weighton durationalprobabilities (because of the highdimension- developedto overcomethis inadequacy by introducingstate-dependent ality of the featurevectors typically used). This work exploresthe ben- polynomialregression functions on time that serveas the time-varying efitsthat can be gainedin speaker-independentcontinuous speech rec- meansin the HMM's Gaussianoutput distributions[e.g., L. Deng, ognition from more accurate duration modeling and automatically SignalProcess. 27, 65-78 (1992)]. Recently,Aksmanovic and Deng estimatinga durationscore weight. In the contextof the stochastic extendedthe above model so that the state-dependentnonstationary segmentmodel, segment durations are modeledusing gamma distribu- processcontains multiple tracks of the polynomialfunctions. This new tionsconditioned on phonetic,lexical, and phrasalcontext, as well as parametricclass of nonstationary-stateHMMs has beenimplemented speakingrate. Robustparameter estimation, a potentialproblem with and evaluated.Experiments on fittingmodels to speechdata, on limited- the large numberof differentconditioning factors, is achievedusing vocabularyword recognition,and on phoneticclassification demon- automaticclustering techniques with a maximumlikelihood criterion. A strated advantagesof the nonstationary-stateHMMs over the tradi- by-productof the clusteringprocedure is a betterunderstanding of the tionalstationary-state HMMs. Detailsof the modelimplementation and relativeimportance of the conditioningfactors. Speech recognition ex- of the experimentalresults will bedescribed. In particular,the focuswill perimentson the resourcemanagement task show that simplecontext- be on comparisonsbetween uses of single-trackand multiple-trackre- independentgamma distributions give similar results to nonparametric gressionfunctions defined within the HMM states,and on comparisons relativefrequency models, and that error can be reducedby more than amonguses of varyingorders of the state-dependentpolynomial regres- 10% by conditioningmodels on such factorsas prepausalposition, sion functions. speakingrate, and lexicalstress.

1:15 1:45 2pSP2. A corpus-basedmodel of interstrese timing and structure. Joan Bachenko and William A. (3ale (AT&T Bell Labs., 600 2pSP4. Duration modelingwith hidden Markov models. L. F. M. Mountain Ave., Murray Hill, NJ 07974-0536) ten Bosch,X. Wang,and L. C. W. Pols (Inst. for PhoneticSci., Univ. of Amsterdam, Hcrengracht 338, 1016 CG Amsterdam, The Studiesof interstressintervals tend to be moresuggestive than con- Netherlands } clusivebecause they rely on relativelyfew speechsamples. The study reportedhere is basedon observationstaken from 32 000 intervalsin the In hiddenMarkov modeling(HMM) of speechsignals, the statistics read speechof 106 speakers.A phonerecognizer was usedto labelthe of speechcharacteristics are representedby HMM parametersafter the onsettimes of each phone;intervals were identifiedas the spanbetween HMM training.This procedureis purelystatistical. This studyconcerns stressedvowel onsetsand each interval was classedaccording to its the incorporationof explicitknowledge into the HMM training.There- structure (the number of consonantsand reduced vowels it contained) fore one specificparameter, i.e., segmentduration, was selected.In as well as duration.The data showedstrong regularities in the depen- orderto studythe relationbetween duration and HMM modeling,three denceof timeon classification.A modelmixing duration, interval struc- typesof durationPDFs (DPDFs) are distinguished:(A) the DPDF ture, and prior probabilitieswas then constructed and testedon phone definedby the segmenteddatabase used (the actual durationhisto- lattices;the latticeswere generated by the phonerecognizer for speech gram); (B) the DPDF definedby the trainedMarkov model(i.e., by from the resourcemanagement task. When durations were fixed but the transitionmatrix), and (C} the DPDF basedon the HMM segmen- interval structurevaried, prior probabilitiespruned incorrect answers tation. While PDF (A) is based on data and PDF (B} is based on the significantlybetter than chance;the mixed model'simprovement was trained model, PDF (C) combinesboth features and is based on the inconclusive.However, when both durationsand interval structurewere availableset of observationsequences. First, an explicitrelation is for- varied,the mixedmodel was clearly superior. The resultsindicate that mulatedbetween topology of the PLU, the three DPDFs, and the so- interval duration and structuremight be a link betweenspeech and calledPad6 expansion. By usingthe generatingfunction of the PDPT, it grammarin humanand machinespeech recognition. is possibleto relatetopological properties of PLUs on the onehand and

1:30 algebraic properties of the DPDF on the other. Second, relations be- tween those PDFs are presentedby usingtwo databasescontaining 2pSP3. Speech recognition using hidden Markov models with identicaltexts, bat read aloudwith a normaland fast speakingrate. This multiple-track polynomial regression functions as nonstationary procedureallows a comparisonbetween variations in the phoneticseg- states. M. Aksmanovicand L. Deng (Dept. of Elec. and Cornput. ment duration and the HMM parameters.

1797 J. Acoust. Soc. Am., Vol. 94, No. 3, Pt. 2, Sept. 1993 126th Meeting: Acoustical Society of America 1797 2:00 [J.'t Hart et aL, A PerceptualStudJ, of lntonatior•,4n Experimental- phoneticStudy to SpeechMelody (Cambridge U.P., Cambridge,1990)] 21•P5. High-resolutionand efficientmultiple-string hylmtbesization is used.The setupof the algorithmis basedon (A} the extractionof two usinginterword models. Wu Chou,Tatsuo Matsuoka, Biing-Hwang time-varyingfeatures (pitch, and a featurecalled vowel strength), fol- Juang,and Chin-Hui Lee (AT&T Bell Labs.,600 MountainAve., lowed by (B) a searchfor characteristicmovements over time in the Murray Hill, NJ 07974) resultingfeature set, (C) a decisionprocedure similar to a lineardis- A new accuratestring hypothesization algorithm to find multiple- eriminantanalysis, and (D) the useof an intonationgrammar. Without stringhypotheses for speechrecognition is proposed.The algorithm using(D}, a classificationrate of 81% is attainedby usingthe database differsfrom the conventionalN-best search algorithms in that it allows of 249 semispontaneoussentences, spoken by morethan 40 maleand the useof the samelong-term language (bigram) models and the same femalevoices. Invoking the grammar[step (D)], at least 6% of the setof subwordmodels, including the interword models, to performboth remaining19% errorscan be resolvedby disambiguatingphonetic can- forward tree searchand backwardtree-trellis stack decoding. The pro- didates.The approachtoward the automaticrecognition of pitchmove- posed.4*-based backward tree-trellis stack decoding can handle inter- mentsis essentiallydifferent from the approachfollowed in speechseg- word unitsat the word boundaries,including the word boundariesof ment recognitionsystems based on hidden Markov modeling.This one-phonewords. Therefore, the interwordcontext dependency is ex- differencewill be discussed.Although the algorithmis developedfor actlypreserved in bothforward and backward multiple-string hypoth- Dutch speechmaterial and for the labelsas definedin the IPO intona- esessearch. The searchefficiency is maximizedby applyingthe same tion labelingsystem, the methodis generallyapplicable to other lan- high-resolutionacoustic and language models in bothsearch directions. guagesand to other (consistent)intonation labeling systems. When the searchheuristics are used,the proposedapproach provides a more accuratestring model matchingthan that of the conventional time-synchronousbeam search decoder. The proposedalgorithm was 2pSPS. Artificial conversationalspeech signal generationmethod for testedon 24 000 connecteddigit stringsrecorded over the telephone measuring characteristics of devices operated by speech signals. networkand collectedfrom ten regionsacross the United States.Using a set of intetmord subword unit models, the test results showed that Hiromi Nagabuchi,Kanako Satoh,and Nobuhiko Kitawaki (NTT Labs.,Midori-cho, Musashino-shi, Tokyo, 180 Japan) 62.4%string errors can be corrected if thesecond-best string hypothesis can be usedto replacethe wrong strings.The string error rate was A methodfor generatingan artificialconversational speech signal as decreasedfrom 2.75% (657) to 1.0% (247) usingthe top two string theinput test signal in measuringthe characteristics of devices operated hypotheses. by speechsignals, such as speechdetectors, voice switches, and echo controllersis proposed.A state transitionmodel among talkspurt, 2:15-2:30 Break pause,double-talk, and mutualsilence in conversationalspeech signals was introduced to simulate the statistical characteristics of these states in real conversationalspeech signals. This modelassumed that the cu- 2:30 mulativedistribution of the durationtime in eachstate is exponential. 21•P6. Context-dependentacoustic subword modeling for connected During talkspurtintervals, an artificial voice was generatedusing a digit recognition. Chin-Hui Lee, Wu Chou, Biing-Hwang Juang, speechsynthesizer that controlledthe spectrumand sourcecharacter- LawrenceR. Rabiner,and Jay G. Wiipon (AT&T Bell Labs., 600 isticsindependently. This artificialsignal generation method can gener- Mountain Ave., Murray Hill, NJ 07974) ate a signalwith givencharacteristics by changingthe valuesof system parameters,such as the averageduration time of eachstate, transition Accurateand robustconnected digit recognitionis essentialfor a probabilityfrom one stateto another,and LPC (linear predictivecod- widerange of telecommunicationservices. Based on trainingand testing ing) parametersthat expressshort-term spectrum variation. The effec- usingonly clean networkdigit data, and usingthe samewhole-word tivenessof this artificial signalwas demonstratedwhen usedto measure model architectureas in the TI/NIST connecteddigit testing,the string 1becharacteristics of a speechdetector. error rate increasedfrom lessthan 1% to more than 5%. The perfor- rnancedegraded even further when evaluatedon data collectedwith 3:15 different network conditions. Most of the observed errors were caused by changingchannel characteristics, highly variabledigit pronuncia- 2pSP9. A speechseparation algorithm that is robust to reverberation. tions,and inadequatemodeling of cross-digitcoarticulation. Results are Philip N. Denhighand HoogyueLuo (Schoolof Eng., Univ. of Sussex, presentedfor a numberof context-dependentwhole-word and subword Falmer, BrightonBNI 9QT, UK) modelingtechniques developed to overcomesome of the aboveprob- An algorithm has been developedthat can segregateoverlapping lems. The most effectiveone is a new acousticsubword modeling ap- voicesby exploitingbarmonicity. It is primarily a monaurai method proach that assumesthat each digit model consistsof three parts, that relieson tracking pitch during the voicedparts of speech,and it namely,head, body, and tail subwordunits. Multiple heads and tails are doesthis successfullyin spiteof the spectralmodifications imposed by also allowed,one for each of the l I possiblepreceding and following room reverberation.The incomingwaveform is divided up into frames digits and the background.Cross-digit coartieulation is modeledby that undergospectral analysis by meansof the FFT. Pitch determina- connectingthe pair of digitsthrough the correspondingtail and head units.Testing on about 12000 digit strings,collected from fiveregions, tion is basedon the subharmonicsummation method, but trackingcon- straintsare imposedthat improveperformance. First, the continuityof this new model architecturereduced the string error rate to under 2%. pitch is exploitedby limiting the searchfor harmonicsto the regions correspondingto the harmonicsof the previouspitch measurement. 2:45 Second,a conditionis imposedwhereby the amplitudeof the harmonics 2pSP7. On the automatic classificationof pitch movements. L.F. cannotchange significantly between frames. The combinationresults in M. ten Bosch (Inst. for PerceptionRes./IPO, P.B. 513, Eindhoven, a "two-dimensionalharmonic sieve" that segregatesvoiced sounds. A The Netherlands) remainingproblem is that of associatinga separatedvoice with the correctspeaker when trackingis lost, for example,after a gap in voicing The designof an algorithmthat elassifiespitch movementsis dis- or after the pitch frequenciescross. For this, a binaural cue is invoked cussed.The algorithmconsists of two steps:(a) a trainingphase, which that relieson the averagedifference of arrival time of the relevant har- is basedon a labeled training corpus of 249 grammatical Dutch sen- monicsof one voice betweentwo microphones.This also provesto be tences, and (b) the recognition phase. The IPO labeling system robust to reverberation.

1798 J. Acoust.Soc. Am., VoL 94, No. 3, Pt. 2, Sept. 1993 126th Meeting:Acoustical Society of Amedca 1798 TUESDAY AFTERNOON, 5 OCTOBER 1993 COLUMBINE ROOM, 12:55TO 3:30 P.M.

Session2pUW

Underwater Acoustics: Seabed Acoustics

F. Michael Pestorius, Chair AppliedResearch Laboratories, University of Texas,Austin, Texas 78713-8029

Chair's Introduction--12:55

ContributedPapers

I:00 During Area CharacterizationTest I (ACT I), conductedin Sep- tember 1992 in 100-fathom water on the West Florida Shelf, acoustic 2pUWI. Effects of "realistic" geoacoustic parameters on transmissionmeasurements were made coveringthe band 50 Hz to 1 frequency-dependentbottom loss. Robert D. Stoll (Lamont-Doherty kHz usingexplosive charges detonated at 90-m depth.The testsite had Earth Observatoryof Columbia Univ., Palisades,NY 10964) a sand-silt-claybottom with a gentleslope of 0.135ø, and up, down, and Recent field studieshave shown that seismicvelocity and attenua- cross-slopetransmission data to ranges of 40 km were collectedon tion gradientsvary rapidly in the sedimentsimmediately below the collocated25-element vertical and horizontal hydrophoneline arrays. seafloor.These variationshave an importanteffect on the frequency- The low seastates and downwardrefracting acoustic conditions preva- dependentbottom loss that is predictedfor wavesentering the bottomat lent during ACT I ensuredthat transmissionloss was controlledby low grazingangles for severalreasons. The more obviousreason is the geometricspreading and bottom interactions.Transmission loss as a variable path length traversedby the shallowdiving wavesthat are functionof range,frequency, and receiverdepth has beendetermined returned to the water column; however,a secondimportant reason and comparedfavorably with predictionsfor both the fiat and sloping appearsto be the conversionof somep-wave energy to s wavesresulting bottom cases.In addition, the multipath temporalstructure and the from the weak couplingbetween the two wave typesthat is causedby verticalarrival structureof the receivedsignals have been analyzed and the high-velocitygradients near the bottom. Comparisonsof bottom have indicated the role of bottom and subbottom characteristics to the losscomputed using the conventionalconstant gradient modelsand propertiesof the receivedsignal. These analyses of the signalstructure variable-gradientmodels based on recentfield measurementsshow sig- have highlightedtransmission mechanisms not readily apparent in nificantdifferences in bottom lossas a function of frequency.The ad- transmissionloss data and haveemphasized the importanceof knowing ditionaleffects of p- to s-waveconversion are alsoillustrated. [Work subbottomstructure to a detailed understandingof shallow water trans- supportedby ONR, Code 11250A.] missionover sandbottoms. [Work supportedby the ARPA Adverse EnvironmentsProgram.] 1:15

2pUW2. Seismoacousticbeamforming with a linear array of 1:45 geoidhoneson the seafloor. J. A. TenCate, T. G. Muir, J. A. Shooter, J. F. Manning (Appl. Res. Labs.,Univ. of Texasat Austin,Austin, 2pUW4. Complex effective depth and mode eigenvaluesfor a layered TX 78713-8029),•.. Kristensen,A. Caiti, and E. Michelozzi elastic waveguide. C. T. Tindie and N. R. Chapman (Defence Res. (SACLANT UnderseaRes. Ctr., 19026 LaSpezia,Italy) Establishment Pacific, FMO Victoria, BC V0S lB0, Canada)

Experimentswere carried out in theStraits of Sicily,Malta Channel The complexeffective depth [Z. Y. Zhang and C. T. Tindle, J. where the seaflooris a relatively fiat silty sedimentsome 150 m deep. A Acoust.Soc. Am. 93, 205-213 ( 1993)] hasbeen investigated for a shal- lineararray of ten verticallygiroballed geophones with elementsepara- low waterwaveguide with a layeredelastic bottom. For multiplelayers, tions of 5 m was laid out on the seafloor. Measurements were made on both the complexeffective depth and the reflectioncoefficient for the seismicfields created by explosiveshots. Similar experiments were per- bottomhave oscillatorystructure as a resultof resonanteffects in the formedin Vestfiord,Norway, where the seaflooris mudover glacial till. layersof the sediment.Under theseconditions and for elasticlayers, The seismicwaves of primaryinterest at thesesites are the dispersive someof thenormal mode eigenvalues can be difficult to find,as a simple Seholtewaves. Group velocitydispersion curves from severaldifferent modecounting procedure is not available.The complexeffective depth shotswere derived using the multiple-filtermethod and show both sites leadsto a formulationof a eigenvalueproblem in termsof a phase to be isotropic.From these curves the phasevelocity as a functionof integral.The phaseintegral is a functionof complexwave number and frequencywas obtained.A beamformingalgorithm was implemented a normalmode exists whenever it is a multipleof •r. A path existsin the that accountedfor the changein seismicvelocity with frequency.This complexplane along which the phaseintegral is real and monotonic. enabledthe array to be beamsteeredon the shotsignals providing array The path passesthrough all eigenvaluesfor both trappedand leaky responsesat variousfrequencies. The resultingdirectivities and sidelobe modes and these can be found systematically. [Work supported by characteristicswere in good qualitativeagreement with array theory. DND.] Sinceseismic velocities were quite low (50-130 m/s), narrow beams wereformed at low frequencies;half-power widths at 18ø at 7 Hz to 13ø at 11 Hz were obtainedwith an array only 50 m in length.[Work 2:00 supportedby DefenseAdvanced Research Projects Agency, Maritime SystemsTechnology Office.] 2pUWS. Influence of geoacousticmodeling on predictability of low-frequency propagation in range-dependent, shallow-water 1:30 environments. R. J. Cederberg, W. L. Siegmann, M. J. Jacobson (Rensselaer Polytech. Inst., Troy, NY 12180-3590), and W.M. 2pUW3. Low.frequencyacoustic transmission at a shallowwater site Carey (Advanced Res. ProjectsAgency, Arlington, VA 22203-1714) in the Gulf of Mexico. Peter G. Cable (BBN Systemsand Technol., Union Station, New London, CT 06320-6147) In a previousstudy of predictabilityof relativeintensity and hori-

1799 d. Acoust.Soc. Am., Vol. 94, No. 3, Pt. 2, Sept. 1993 126thMeeting: Acoustical Society of America 1799 zontal wave numbersby the authors,parabolic approximations were approachhas advantages over averages of multipleruns of deterministic used in range-independentshallow-water waveguides. Uncertainties in modelsover realizations of sedimentvelocities. Features of the average sedimentproperties were found to be the mostsignificant factor limiting solutiontransmission loss and phasechange, preserved by this algo- predictionaccuracy. In this paper, modelsof bottom sound-speedpro- rithm, will be discussed.[Work supportedby ONR/NRL-SSC and filesthat take into accountsediment consolidation are developed,and ONR Young Navy ScientistProgram.] their effectson propagationmodel predictionsin range-dependenten- vironmentsare examined.Environmental parameters correspond to 3.-O0 thosenear the siteof a recentNew JerseyShelf experiment site. Using boreholedensity data and Biot-Stoll theory, a functionalform for po- 2pUWg. Two-dimensionalmodeling of low-angle backscatter from rosityin a homogeneousconsolidated sediment is derived.Correspond- geologicallyrealistic seafloors. R.A. Stephenand S. A. Swift (Dept. ing sound-speedprofiles for different sedimenttypes are then con- of Geol. and Oeophys.,Woods Hole Oeeanogr.Inst., WoodsHole, MA strncted.Predictions from modelsconsisting of consolidatedsediment 02543) layersthroughout the bottomare comparedwith resultsfrom casesfor which sound-speedis comprisedof piecewiselinear segments.In addi- The numerical scatteringchamber has been used to quantitatively tion, bottomsound-speed range dependence was modeledwith discrete predictlow-angle backscatter coefficients for a suiteof seafloormodels. as well as continuouschanges between profiles for variations of the A number of issueshave been addressed:(a) How finely does seafloor geophysicalparameters in this area and no substantialdifference was bathymetryneed to be resolvedin order to predict the backscattered observed.Comparison of experimentaldata with modelpredictions in- field?Corollary issues in this area are (i) at what resolutioncan onego corporatingrange dependenceare discussed.[Work supportedby from a deterministicto a stochasticrepresentation and (ii) how should ONR.] one interpolatebetween bathymetric data points7(b) How important are shear (rigidity) propertiesof the sedimentand basementin a pre- dictive model of seafloorbackscatter? (c) How important is intrinsic 2:15-2:30 Break attenuation(anelasticity) in a predictivemodel of seafloorbackscatter?. (d) How do the magnitudeand mechanismsof backscattervary with 2:30 increasingsediment cover?. (e) How effectiveare isolatedfacets on the seafloorin generatingstrong backscatter7. (f) Can realisticvolume het- 2pUW6. Simple 3-D Gaussianbeam calculationsfor a standardand a erogeneitieswithin the sedimentand basementgenerate comparable modified wedge. Homer Bucker (NCCOSC, RTDE DIV, San Diego, backscatterlevels to realistic seafloorroughness? These issueswill be CA 92152-5001) discussedby comparingbackscatter coefficients for variousseafloor rep- In manypractical Navy acousticsystems, the soundfield is strongly resentations. affectedby three-dimensionalvariations in the oceanbottom. A theory is presentedfor a simple Gaussianbeam propagationmodel that ac- 3:15 counts for full three-dimensional effects of the ocean bottom. The Gaussianbeam formulationis especiallyuseful because it definesthe 2pUW9. Long-rangecontinuous-wave and time-domainsimulations of soundfield in termsof the travel timesand anglesof eigenraysthat are oceanacoustic scatter from a subbottomartelastic corner. Stanley A. neededfor the analysisof acousticsystems. Examples will be shownfor Chin-Bing {Naval Res. Lab., StennisSpace Center, MS 39529-5004), the standardwedge calculation [Deane and Buckingham,J. Acoust. JosephE. Murphy, and Gongqin Li (Univ. of New Orleans, New Soc.Am. 93, 1319-1328 {1993)] and for a wedgemodified by an island Orleans, LA 70148) and a knoll. Recent long-rangeacoustic reconnaissance experiments done in the mid-Atlantic ridge region show strong reverberationfrom many ocean bottomfeatures. Two typesof featurescharacteristic of this region,and possiblecontributors to this reverberation,are seafloorridge corners--- 2pUW7. Parabolic equation average propagation in the presence of rapid range variation in a sedimentlayer. Roger M. Oba (Acoust. "inner" cornersand "outer"corners---formed by two ridgefaces inter- seetingat near-rightangle•. Corners formed by facesintersecting at near Simulation,Code 7181, Naval Res. Lab., StennisSpace Center, MS 39529-5OO4) 90ø are termed "inner" corners and those formed by facesintersecting at near 270• are termed "outer" corners.Via computersimulations, the The routinefor computingthe averagesolution to the generalized effectsof an anelasticseafloor corner on the acousticfield originating parabolic equation JR. M. Oba, J. Acoust. Soc. Am. 90, 2300(A) from a distantsource have beeninvestigated. Both an "inner" corner ( 1991)] in the water worksfor propagationwith sedimentsmodeled by and an "outer" cornerwere usedin the study.The effectsof thin sedi- fluid layers.It can be usedin a "marchingalgorithm" from one range ment layers coveringthe cornerswere also investigated.Simulations stepto another,especially if they are statisticallyindependent. Because were made usingcontinuous-wave (cw) computermodels: the parabolic the algorithmrelies upon analyticforms of matricesfor horizontalprop- equationmodel, FEPE,for long-rangepropagation of the acousticfields agationof vertical modes,a natural limit existswhen (a) the sediment to and from the vicinity of the corners,and the seismoacousticfinite- variation is rapid comparedwith wavelengthand depth, {b) the sedi- element model, SAFE,to determine the scatteredfields from the anelastic ment variationis statisticallyindependent in each range step,and (e) corners. Time-domain calculations were obtained from FFTs of the cw the probabilitydistribution over the velocityprofile ensemblein each fields.Examples will be presentedthat showthe effectsfrom thesetwo rangestep is identical.Its applicationto the casewhere the probability cornertypes. [Work supportedby NRL, ONR, and the ONR Acoustic distributioncan be parametrizedby one variableis demonstrated.This ReverberationSRP.]

1800 J. Acoust.Soc. Am.,VoL 94, No. 3, Pt. 2, Sept. 1993 126th Meeting:Acoustical Society of America 1800 WEDNESDAY MORNING, 6 OCTOBER 1993 LOWER LEVEL PLAZA, 8:00 A.M. TO 3:00 P.M.

EquipmentExhibit

See pages xxxi and xxxii for the list of exhibitors.

WEDNESDAY MORNING, 6 OCTOBER 1993 TERRACE ROOM, 8:45 A.M. TO 12:00 NOON

Session 3aAO

AcousticalOceanography: Acoustical Determination of Ocean Parameters and Processes

Jeffrey A. Nystuen, Chair NOAA-AOML, AcousticsDioision, 4301 RickenbackerCauseway, Miami, Florida 33149

ContributedPapers

8:45 nancefrequency of a bubbleincreases when it is deformedfrom a spher- ical shape, but show that it is also independentof the direction of 3aAOl. Underwater soundproduced by rainfall: Secondarysplashes excitationand increasesmore quickly with aspectratio for cylindrical of aerosols. Jeffrey A. Nystuen (Ocean Acoust. Div./AOML, 4301 than for prolate spheroidalbubbles. The frequencywidth of the reso- Rickenbacker Cswy., Miami, FL 33149) and Herman Medwin nance increaseswith the deformationin both cases,but Q falls more (Naval PostgraduateSchool, Monterey, CA 93943) quicklyfor the cylindricalbubble. Increasing the deformationcauses the Earlier studies have identified three sources of underwater sound scatteringamplitude to decreaseand its angulardistribution to change. productionfrom raindrops:the initial impact,a bubbletrapped under- A remarkable result is that for highly deformed spheroidalbubbles wateras the impactcrater closes (type I), and a bubbletrapped under- there is relativelylittle changefrom the sphericalscattering pattern water by a turbulentjet associatedwith the splashcanopy formation obtainedwith an undeformedbubble. In contrast,highly deformed cy- (type II). For naturalrainfall, type l bubblesare associatedwith small lindrical bubblesshow prominentlobes. [Work supportedby ONR raindrops(0.8-1.1 mm diam), while type II bubblesare associatedwith Technology Directorate (Element 602435N) and by the Naval Re- large raindrops (diameter greater than 2.2 ram). Predictionsfor the searchLaboratory, 6.1 Program (Element 601153N). Technical man- soundgenerated by rainfall consideringthese three soundsource mech- agementprovided by NRL-SSC.] anismshave beenconsistently low, suggestingthat an additionalsource mechanismis present.Experimental data will be presenteddescribing a 9:15 new mechanismof bubbleentrapment--namely, bubbles created during the secondarysplashes of drop aerosolsthrown up during the initial 3aAO3. Estimating vertical and horizontal wave-numbertemperature raindropimpact (type III). For the raindropsizes studied (large rain- spectraof a buoyantthermal plume. JohnOeschger (Univ. of Rhode drops, 3.04.7 mm diam), type IIl bubblesoccurred, on average,more Island, Dept. of Phys., Kingston, RI 02881) and Louis Goodman than onceper impact.These bubbles span sizes, resonance frequencies, (Naval UnderseaWarfare Ctr., Newport, RI 02841) and acousticalenergy emissions comparable to the type II bubbles. Acousticscattering from a buoyantthermal plume described by the Considerationof type III bubblesimproves predictions of the underwa- far-fieldBorn approximationresults in a simplerelationship between the ter soundgenerated by rainfall.These predictions are neededto support scatteredpressure field and the scatteringfield; namely, the two are the inversion of the oceanic ambient sound field to estimated rainfall Fourier transformpairs. For media variability, such as the buoyant rate at seaquantitatively. [Work supportedby ONR and NRL/TOWS.] plume where the spatial variability is larger than the Fresnel radius, wave-front curvature must be included to describeexperimental results adequately.Under conditionswhere Taylor's hypothesis is satisfied(the 9:00 time variability is entirely due to the advectionat a constantvelocity of 3aAO2. Resonance scattering from nonspherical bubbles in water. spatialvariability), the effectsof wave-frontcurvature on the scattering C. Feuilladeand M. F. Werby (Naval Res.Lab., StennisSpace Center, processcan be removed.Data are collectedfor simultaneousmultiple MS 39529-5004) bistaticscattering experiments in commonand antiparallelscattering directionsfor the unstableand turbulent plume. Resultsinclude an Submergedbubbles can be treatedas air-filledinclusions in water estimation of the vertical and horizontal wave-number temperature from whichscattering occurs because of the changeof acousticalim- spectraof the buoyantplume. pedanceat the interfacebetween the two media.The T-matrixexpan- siontechnique allows for the generaldescription of scatteringfrom both 9:30 sphericallyand nonsphericallyshaped bubbles. This methodis usedto study the monopoleacoustical resonances of bubblesdeformed into 3aAO4. Barotropic currents, vorticity, and tides in the northcentral elongatedaxisymmetric objects (specifically, prolate spheroids and cyl- Pacific in summer 1987 determined from long-range acoustic inderswith hemisphericalendcaps). The resultsconfirm that the reso- transmissions. Brian D. Dushaw (A.P.L., Univ. of Washington, 1013

1801 J. Acoust. Sec. Am., Vol. 94, No. 3, Pt. 2, Sept. 1993 126th Meeting: AcousticalSociety of America 1801 NE 40th St., Seattle, WA 98105-6698), Peter F. Worcester, Bruce signature.[Work supportedby ONR through Contract No. N00014- D. Cornuelle (Univ. of California, La Jolla, CA 92093-0213), and 93-I-0049.] Bruce M. Howe (Univ. of Washington,Seattle, WA 98105-6698) 10:15-10:30 Break Large-scaledepth-integrated currents, relative vorticity, and tides were measuredin the northcentralPacific Ocean during summer1987 usinglong-range reciprocal acoustic transmissions between transceivers 10:.30 in a triangleapproximately 1000 km on a side.Tidal harmoniccon- stantsfound from the acousticallydetermined currents agree with those 3aAO7. High-resolution backscatter from the Mid-Atlanfie Ridge. foundfrom currentmeters and with the tidal modelsof Schwiderski[E. Nicholas C. Makris, Jonathan M. Berkson, and Richard Menis (Naval W. Sehwiderski,Mar. Geod. 3, 161-255 (1980)] and Cartwrightet al. Res. Lab., Washington,DC 20375) [D. E. Cartwrightet al, NASA Tech. Mere. 104578(1992)]. Sum High-resolutionbackscatter is charted to respectivescattering sites travel timeswere usedto calculatethe baroclinictide isotachdisplace- on the western flank of the Mid-Atlantic Ridge (MAR) by two-way ment. A significantpart of the derivedinternal is deterministic. travel-timeanalysis and beamforming.Since the rangeresolution of the Currentsare calculatedusing the topographicSverdrup balance with low-frequencyFM acousticdata is on the order of the acousticwave- the Fleet NumericalOceanography Center wind field. The measured length (roughly6 m), a bistatiemapping procedure is employedthat time derivativeof the areal-averagedrelative vorticity is insignificantto accountsfor bathymetricvariation and combinescalculations of eigen- the Sverdrupbalance. Currents and vorticity calculated using the Sver- ray pathsand slant range to preciselylocate scattering sites at rangesup drup balanceare an orderof magnitudesmaller than the observations. to roughly one-half a convergencezone from the source/receiver. The magnitudeand variabilityof the large-scalecurrents and vorticity Right-left ambiguityof the horizontal-line-arraydata is resolvedby determinedfrom the Semtner-Chervineddy-resolving model of ocean takingadvantage of the environmentalsymmetry-breaking properties of circulation[A. J. Semtnerand R. M. Chefvia, J. Geophys.Res. 93, transmissionloss, modeledwith the parabolicequation, as well as by 15 502-15 522 ( 1988)] are similar to the direct measurements.[Work inversionof adjacentquasimonostatic observations. Mapped reverbera- supportedby NSF and ONR-] tion and estimatedscattering strength are then projectedonto high- resolutionbathymetry for comparison.For the samescattering site and observationgeometry, it is found that higher-resolutionsignals often yield higherand more localizedscattering strength maxima. This sug- •tAOS, Determining elastic seafloor parameters in shallow water geststhat discreteand spatiallyintermittent scatterers are importantto using ambient noise. Grant B. Deane, Nicholas M. Carbone, and reverberation in the MAR. Michael J. Buckingham (Marine Phys. Lab., Scripps Inst. of Oceanogr.,9500 Gilman Dr., La Jolla,CA 92093-0238) 10:45

The ambient noise field in shallow water contains information about 3aAOS. Model eigenfunefion perturbations and group speed the seafloor. Measurements of the coherence of ambient noise have been tomography. B. Edward McDonald (Naval Res. Lab., Washington, usedsuccessfully [M. J. Buckinghamand S. A. S. Jones,J. Acoust.Soc. DC 20375) and Arthur B. Baggcroer (MIT, Cambridge,MA 02139) Am. 81, 938-946 (1987)] to infer the critical angle of a variety of fluid basements.This techniquehas beenextended to includethe caseof a Certain problems in acoustic tbermometry of ocean elimate shear-supportingbottom. A theoreticalmodel of the ambientnoise in an (ATOC) require evaluatingthe responseof modal group speedsto isovelocity,shallow water channeloverlying an elasticbasement with perturbationsin the ocean sound-speedprofile. Two different ap- independent,randomly distributedsurface sources will be presented. proacheshave been taken recentlyby researchers,resulting in two per- The modelshows that elasticbasements with shearspeed greater than turbation expressionswhose equivalence is not immediatelyevident. 650 m/s have sufficienteffect on the noisefield to enablethe geoacoustic The first approach,used by Lynch et al. [J. Acoust.Soc. Am. 89, 648 parametersof the bottomto be determined.The two main effectsob- (1991)], resultsin an integralequation involving the frequencyderiva- servedare an asymmetryin the verticaldirectionality and the arrivalof tive of the eigenfunctions.The secondapproach, under current investi- energyat anglesgreater than the critical.[Work supportedby ONR.] gation,yields an integralequation involving the responseof the eigen- functionsto sound-speedperturbations. The two expressionsare shown to be equivalent by means of their projectionsonto the set of modal 10:00 eigenfunctions.These results arc discussedin relation to group travel- time tomography. 3aAO6. Angular dependenceof acoustic backscatter from simulated anisotropic Goff-Jordan seafloor relief. V. Premus and D. 11.4}0 Alexandrou (Dept. of Elec. Eng., Duke Univ., Box 90291, Durham, NC 27708-0291 ) 3aAO9. Effects of perturbationson long-rangepropagation. William A. Kuperman?Michael D. Collins,B. EdwardMcDonald (Naval The angulardependence of 12-kHz acousticbackscatter from sim- Res. Lab., Washington,DC 20375}, and Kevin D. Heaneya) ulatedanisotropic centimeter-scale bottom relief is investigatedfor an- (PlanningSystems, Inc., McLean, VA 22102) glesof incidencebetween 0' and 20ø. Numericalsimulations of back- scatteringstrength as a functionof elevationand azimuthare obtained Resultsof numericalmodeling of long-range(greater than 500-kin) by mergingthe Kirchhoffapproximation with realizationsof seafloor low-frequencyacoustic propagation in the oceanhave been presented topographyderived from the Goff-Jordansurface model. The surface previously.These results were in qualitativeagreement with measure- model has been theoreticallyextrapolated to the small-scaleroughness mentsfor the Heard Island FeasibilityTest and the SLICE89 experi- regimeby connectingthe spatial samplinginterval with the incident ments.To quantifythe differencesbetween experimental and parabolic acousticwavelength and defining the characteristicwave numbers,k n equation(PE) results,time-dependent modal decompositionwas ap- and k,, of the 2-D surfaceroughness spectrum to be O(m-1). The plied to the receivedsignals. This modal tomographygives us an indi- viability of extendingthe (loft-Jordan modelto centimeter-scalerelief is cation of the depth-dependentdifferences between the actual and as- supportedby the recentobservation of power-lawspectra within the sumedsound-speed profiles. This work is extendedto look at the effects spatialfrequency range of 0.01 to 1.0 cycles/era[D. R- Jacksonand K. of smallperturbations in the sound-speedfield (i.e., internalwaves} on B. Briggs,J. Acoust.Soc. Am. 92, 962-977 ( 1992)]. The resultsdem- the arrivalpattern. Internal waves were modeled using a statisticalre- onstratethat backscatteringstrength can be very sensitiveto azimuthal alization of the Garrett-Munk spectrum.Results of the effectsof inter- variationin surfacecorrelation properties. It is also observedthat the nal waveson specificdeep oceanmode functionsand model group spectral roll-off parameterhas an impoRant impact on the minimum velocitiesare presented.a)Present address: Marine PhysicalLabs., degreeof anisotropythat can be identifiedby the backscatteredacoustic ScrippsInst. of Oceanogr.,UCSD, La Jolla, CA 92093.

1802 J. Acoust.Soc. Am., Vol. 94, No. 3, Pt. 2, Sept. 1993 126th Meeting:Acoustical Society of America 1802 11:15 in the analysisof the averagedtime delays,which may indicateglobal warmingtrends due to the greenhouseeffect. The 3-D propagation 3aAO10. Global acousticmapping of oceantemperatures (GAMOT). modelsthrough random media are extremely complicated. Propagation JohnL. Speisbergcr(Dept. of Mctcorol.and the Appl. Res.Lab., 512 of modelequations is governedby a setof matrixdifferential equations, Walker Bldg., Penn State Univ., UniversityPark, PA 16802), Dan whoseelements are obtainedby multidimensionaloscillatory integra- Frye (Woods Hole Oceanogr. Inst., Woods Hole, MA 02543), tion. Analyticaland numericalstudies have beenconducted that show Harley Hurlbutt, Joe McCaffrey (Naval Res. Lab., Stennis Space the feasibilityof computingthe matrix elements1000 timesfaster than Center, MS 39529), Mark Johnson (Univ. of Alaska, Fairbanks, AK was previouslydone. The matrix equationis solvedby well-knownor- 99701), and James O'Brien (Florida State Univ., Tallahassee, FL dinary differentialequation methods. The effectsof frequency,trajec- 32306) tory, sound-speedprofile, bathymetry, and the variancesof internaland Successfulfeasibility experiments for mappingglobal ocean warm- surface waves will be discussed. ing and climatevariability with soundhave been conducted since 1983 11:45 [J. L. Spiesbergeret al., J. Acoust.Soc. Am. 92, 384-396 ( 1992)].The GAMOT groupis developingtwo newhigh-technology instruments for 3aAO12. Sound velocity in the deep sea: Examination of making thesesame measurements in near-realtime at one-eighththe measurement data obtained from a deep submergencevehicle. cost of our previousmeasurements taken from sourcesand receivers Toshio Tsuchiya, Yasutaka Amitani, Hiroshi Ochi (Deep Sea connectedto shorewith cables.One instrumentis a surfacesuspended Technol. Dept., Japan Marine Sci. and Technol. Ctr., 2-15 acousticreceiver (SSAR), whichdangles a hydrophonearray beneatha Natsushima-cho,Yokosuka, 237 Japan), and Toshiaki Kikuchi freelydrifting surface unit. The otherinstrument is a subsurfaceauton- (Natl. DefenseAcad., 1-10 Hashirimizu, Yokosuka,239 Japan) omousmooring equipped with an acousticsource and a new telemetry An accurateequation of soundvelocity in seawateris a veryimpor- schemefor removingtravel time changesdue to mooringwander in real tant factor for oceanacoustic tomography according to acoustictravel time. Climatic temperaturevariability from past and presentexperi- time acrossthe ocean.A soundvelocity equation has been examined in mentsis studiedwith state-of-the-artocean models. A programupdate a laboratoryunder various values of temperature,salinity, and pressure will be presented.[Work is supportedby the .AdvancedResearch by Wilson,DelGrosso, Chen, and Millero. However,as direct measure- ProjectsAgency.] ment in the deep-seaarea is very difficult,these data havebeen very limited. Therefore,recently the soundvelocity was measureddirectly 11:30 more than 50 timesfrom the surfaceto a depth of over 6000 m by a sing-aroundsound velocimeter installed in the manneddeep-sea re- 3aAOll. Error analysis of ocean acoustictomography due to internal searchsubmergence vehicle "SHINKAI 6500" of the Japan Marine waves. J. (}omni and L. Boden (CooperativeInst. for Res. in Scienceand TechnologyCenter. Data wereobtained with temperature, Environmental Sci./NOAA, Campus Box 449, Boulder, CO salinity,and pressurevalues in the westernPacific Ocean area. Then, 80309-0449) the measureddata were comparedwith the calculatedvalues of the A realisticerror analysisof the temperaturevariability of the oceans equationof Wilson, DelGrosso,Chen, and Millero. The comparison as probedby oceanacoustic tomography is presented.Travel-time er- resultindicated a trend: Soundvelocity in the deepsea is greaterthan rorsresulting from fluctuatinginternal and surfacewaves are important valuesof variousequations according to the pressureeffect.

WEDNESDAY MORNING, 6 OCTOBER 1993 SPRUCE ROOM, 9:00 TO 11:15 A.M.

Session 3aEA

EngineeringAcoustics: Acoustic Measurements and Instrumentation

Edward F. Rynne, Chair Naval Command, Control and Ocean Surveillance Center, RDTE Division, Code 711, 496640 Gate Road, Room 19, San Diego,California 92152-6242

ContributedPapers

9:00 high-ordermodes are attenuatedbelow their cutofffrequency in an acousticwaveguide. Rayleigh's second perturbation is presentedas 3sEA1. Rayleigh's horn equation. John T. Post and Elmer L. "Rayleigh'shorn equation." The acoustic impedance at thethroat of the Hixson (Dept. of Elec.and Comput. Eng., Univ. of Texas,Austin, TX horn and soundpressure interior to the horn as predictedfrom Ray- 78712) leigh'stheory are comparedwith laboratorymeasurements. Rayleigh'swork on tapered waveguides isapplied to acoustichorus. The acousticvelocity potential is expandedin a perturbation-typesolu- 9:15 tion andthe firstperturbation is shownto producethe Websterhorn equationon-axis, but predictsprogressive waves to havecurved, or 3aEA2. High-fidelity displacementsensors for acoustic emission bulging,phase fronts. Applicability of Rayleigh'sfirst perturbation is source characterization. C. M. Fortunko, M. A. Hamstad, and D. shownto be identicalto the estimategiven by Piercefor applicabilityof W. Fitting (Natl. Inst. of Standardsand Technol., 325 Broadway, the Websterhorn equationand both of thesereveal that the Webster Boulder, CO 80303) equationcannot predict a "cutoff"frequency. When operatingat the "cutoff"frequency predicted by Webster,any practical hon. is tooshort Acousticemission (AE) sourcecharacterization requires the useof to load an acousticsource, so the performanceis virtually the sameas broadband,typically 20 kHz-2 MHz, "point-contact"sensors. Gener- lettingthe source radiate into free-space; but the horndoes not attenuate ally, AE sensorsbased on the NIST "conical"transducer approach can theprogressive wave below the "cutoff" frequency in thesame way that meetthis requirement.However, because naturally occurring AE events

1803 J. Acoust.Soc. Am., Vol. 94, No. 3, Pt. 2, Sept. 1993 126th Meeting:Acoustical Society of America 1803 are considerablyless energeticthan those produced by artificial AE are compared.With both methods,we can detect cracksas small as 0.1 sources,optimization of the sensorsignal-to-noise performance is of in. Examplesof the resultsobtained for metal and concretebeams will criticalimportance. Using a computermodel, a varietyof sensor-design be shown.[Work supportedby NSF Grant no. MSS-9024224.] approacheshave been studied, with particularemphasis on transducer/ preamplifier/specimencompatibility issues. In this paper, computer- 10:00 modelpredictions are comparedwith the resultsof experiments.The useof differentpiezoelectric transducer materials--PZT-5A, lead met- 3aEAS. Ultrasonic detectionof icing onsetand accretionthickness on aniobate,LiNbO 3, X-cut quartz,and PVDF--is considered.It is shown aircraft. David K. Hsu, Frank $. Margetan,Samuel J. Wormley (Ctr. thatceramic materials exhibiting the highestdielectric constants, 53, for NDE, Iowa State Univ., Ames, IA 50011), and $effrcyA. are bestsuited for most high-performanceAE sensorapplications. In Simpson (J-TeeAssociates, Inc., CedarRapids, IA 52401) addition,the impactof preamplifierinput capacitance,including the A majorenvironmental in aviationis icebuildup on aircraft. Miller effect,and specimenmechanical impedance on the performance The developmentof a detectorfor the onsetof icingand for accretion of a "point-contact"sensor is discussed.In particular,using the com- thicknessmeasurement using ultrasonic waves is described.The detec- puter model, the limitationsof sensorsthat use piezoelectricceramics tion is basedon reflectivitychange at a metal-iceinterface and basedon and single-crystalmaterials are examined.It is shownthat in certain echo-rangingtechniques using pulses of longitudinaland shearwaves. situations,such as very thin metalplates and materials that exhibitvery The detectoris sensitiveto the onsetof icing;ice layers as thin as0.002 low characteristicimpedances, sensors that use piezoelectricceramic in. can bc detected and accurate thickness can be measured from 0.015 and single-crystaltransducers may not be the bestchoice. Therefore, to in. onward.By usingthe ratio of an interfaceecho and an echofrom an addresssuch cases, alternative sensor approaches are needed. internal referencereflector, the quantitativemeasurement results are immuneto changesin transducercoupling conditions. Using a combi- 9:30 nation of longitudinaland shearwaves, the detectorcan alsodifferen- tiatebetween ice and water. Laboratory tests were made for anticipated 3aEA3. Modulation-frequencydependence of the nonlinearsensitivity complications,such as roughor tilted surfaceof ice buildupand accre- of a Briiel & Kj•er 8103 hydrophonein parametric demodulationof tionof glazeversus rime ice. [Work supported by an Army SBIR grant amplitude-modulatedultrasound. Shengke Zeng and Richard B. to J-Tee Associates,Inc.] Beard (Biotaed.Eng. and Sci. Inst., Drexel Univ., Philadelphia,PA 19104) 10:15 The interferencedemodulation by the nonlioearityof hydrophones cannotbe ignoredin parametricdemodulation of amplitude-modulated 3aEA6. Applicationof nonlineardynamics for noise reductionin (AM) ultrasoundin the near-fieldmedia, where the intensityof the measured signatures containing broadband information. Ronald primaryincident waves on hydrophonesis very high. The interference Hughes (Radix Systems,Inc., 6 Taft Ct., Rockville,MD 20850) demodulation,which is causedby thesecond-order sensitivity of a hy- Nonlineardynamics has been of greatacademic interest in recent drophone,N(f), is proportionalto thesquare of theincident pressure years.Its conceptshave been employed as a foundationfor modeling p2[Moffett and Blue, Naval Underwater System Center, Tech. Memo. nonlinearprocesses in diversefields extending from economic trends to 801! 50 ( 1980);Humphrey and Hsu, Proceedingof SpecialistsConfer- medicaldysfunctions. Although the developments of nonlinear dynam- enceon UnderwaterAcoustic Applications (1980)]. It is foundin the ics conceptsin acousticsare sparse,their applicationin acousticshas measurementof parametricdemodulation of AM ultrasoundby a Briiel advantagesover linear techniques in extendingbroadband signatures in & Kj•er 8103 hydrophonethat the N(f) is not only the functionof the high-noiseenvironments. Linear signal analysis approaches are signifi- carrierfrequency f, but alsothe functionof the modulationfrequency cantlylimited when the noise environment is nonstationaryor whenthe F. At a fixedcarrier frequencyf0=2.3 MHz, the interferencedemod- signalduration is short.Furthermore, the applicationof filtersalters the ulationcan be observedat the modulationfrequencies below 6 kHz, and informationcontent of the originalbroadband signals. Nonlinear dy- becomesstronger toward low modulationfrequencies at a distanceof namics methods do not suffer these limitations. Two such methods will 150mm betweenthe transducerand the hydrophone.The interference bedescribed for effectingnoise reduction where the signal-to-noise ratio demodulationby the nonlinearityof the hydrophonecan be distin- is zeroor negativeand where there is no a prioriknowledge of eitherthe guishedfrom parametric demodulation by observingthe directivity pat- signalor the noise.Signals used for demonstrationinclude sinusolds and terndifference between them. N(f, F) is observedin the abovepara- chaoticsequences; additive noise includes uniform and Gaussianran- metricdemodulation to be proportionalto F TM IS. Zheng,Ph.D. domnoise and noise that producesa power spectrum equivalent to that dissertation,Drexel University (1993)]. [Work partiallysupported by of the "clean"sequences. Noise reduction of 15-18dB usingnonlinear Electro-StimCorp.] dynamicswill beshown, and fidelity reproduction ofthe original signal will be demonstrated. 9:45 10:30 3aEA4. Artificial neural nets for acoustic nondestructiveevaluation. PeeterAkerberg, Ben H. Jansen (Dept. of Elec. Eng., Univ. of 3aEA7. On the nonlinearityof exhaustsystem acoustics in firing Houston,Houston, TX 77204-4793), Shall R. Pandya,Zhijing spark-ignitionengines. A. Selamet(Dept. of Mech.Eng. and Appl. Wang, and Robert D. Finch (Univ. of Houston, Houston, TX Mech., Univ. of Michigan,Ann Arbor, MI 48109-2125) 77204-4792) An extensiveamount of literatureis availableon theperformance of Artificialneural networks (ANNs) arebeing used for thedetection automotivesilencers subject to linear acousticdisturbances and no- of cracksin metaland concrete beams and structures. Vibration signals meanor steady-meanflow conditions.The flow throughthe automotive are obtainedfrom thesestructure by impactingwith a small hammer exhaustsystem exhibits, however, a numberof nonlinearphenomena and recordingthe activity of an accelerometerattached to the structure. includinghigh sound pressure levels reaching 180 dB andvarying mean Thesevibration signals are digitized,and the samplesare input to an flow,as well as spatially and temporally changing temperatures. These ANN. Detectionof cracksproceeds in two differentways. For both nonlinearitiesare difficultto treatwith the linearizedacoustic theory methods, the networks are trained on data obtained from intact struc- approachin thefrequency domain. The present study provides experi- tures,but in the caseof the first method,training is haltedonce the mentalresults as well as numerical predictions for a productionvehicle ANN canaccurately predict future samples of thevibration signal from full exhaustsystem (Ford 1.9L Escortengine) and investigates the present and past observations.These ANNs are then fed with data nonlinearities.The study implements a time-domain finite-difference ap- obtainedfrom structures with varying degrees of defects,and the pre- proachto predictthe acoustic performance based on the work of Chap- dictionerror is noted.In thesecond method, training continues after a manet al. [WinterAnnual Meeting of ASME (1982)], whichsolves the smalldefect has been made to thestructure, and the weightsof the nets one-dimensional,variable cross-sectional area, nonlinear balance equa-

1804 J. Acoust.Soc. Am., Vol. 94, No. 3, Pt.2, Sept.1993 126thMeeting: Acoustical Society of America 1804 tionsof mass,momentum, and internalenergy coupled with the equa- domainfor the predictionof the acousticand powerperformance of tion of statefor compressibleflows. Nonlinearities are discussedin view firinginternal combustion engines with full productionexhaust system. of theexperimental data and by comparingthe termsof themomentum balancefrom computationalresults. 11:00 10:45 3•EA9. Determinationof the performanceof soundintensity probes 3aEA8. The effect of vehicle exhaust system components on in standing wave fields. Erling Frederiksen and Jorgcn I. pedormance and noise in firing spark-ignition engine•An Christensen (Dept. of MicrophoneDcvcl., Bdiel & Kj•cr, 2850 experimentalstudy. A. Selamet,M. S. Croy (Dept. of Mech. Eng. N•rum, Denmark) and Appl. Mech., Univ. of Michigan,Ann Arbor, MI 48109-2125), IEC and ANSI standardsthat specifythe performanceof instru- R. A. Kach, and J. M. Novak (Ford Motor Co., Dearborn,MI 48121) mentsfor the measurementof soundintensity are expectedto be re- In vehicleexhaust systems, the soundattenuation and the reduction leasedin the nearfuture. The draftedstandards prescribe the minimum of flow lossesare often competingdemands. The presentexperimental performanceof soundintensity probes in standingwave fields. Gener- studyconsiders a full vehicleexhaust system and investigatesboth the ally, the measurementof soundintensity has the greatestinterest in soundattenuation and the flow performanceof productionconfigura- connectionwith reactivesound fields. Unfortunately, the more reactive tions includingthe catalyst,the resonator,and the muffler.Dynamom- the soundfield, the higherarc the requirementsto tbe instrumentfor the eter experimentshave beenconducted with a firing Ford 1.9-Liter I4 samemeasurement accuracy. As well-definedreactive fields can be pro- Escortengine with speedsranging from 1000 to 5500 rpm. Measure- dueedinside tubes, standing wave tubes have been selected for testingof mentsincluding the flow rates,the temperatures,and the absolutedy- intensityprobes. The standingwave performanceof intensityprobes, namicpressures of the hot exhaustgases at key locations(upstream and equippedwith pressure-sensingmicrophones, has beencalculated and downstreamof everycomponent) with fast-response,water-cooled pi- measured.Results obtained by the two methodswill be shown.A de- ezoresistivetransducers facilitate the calculationof acousticperfor- scriptionwill be given of the calculationmodel and of the specially manceof eachcomponent, as well as the determinationof flow losses designedstanding wave tube that hasa frequency-independentstanding causedby theseelements and their influenceon the engineperformance. wave ratio of 24 dB ( a:0.5 dB) between40 and 500 Hz. This perfor- The presentstudy describes the experimentalaspects of an extensive mancehas beenobtained by terminatingthe test tube with many long effort toward employingnonlinear fluid dynamicmodels in the time and narrow plastictubes.

WEDNESDAY MORNING, 6 OCTOBER 1993 GOLD ROOM, 8:25 TO 11:55 A.M.

Session 3aMU

Musical Acoustics: Mode Studies in Musical Instruments

Uwe J. Hansen, Chair Departmentof Physics,Indiana State University,Terra Haute, Indiana 47809

Chalr's Introductions8:25

Invited Papers

8:30

3aMU1. The physicsof normalmodes. GabrielWeinreich (Randall Lab. of Phys.,Univ. of Michigan,Ann Arbor, MI 48109-1120) Thisis primarilya tutorialpaper to organizeand clarify various concepts whose understanding is required for workwith linearsystems. Among the questions to beaddressed are: What is thedifference between a resonanceand a normalmode? What aboutan antiresonance?How do normalmodes relate to frcc motion?To forcedmotion? Arc there"strong" and "weak" modes? Arc resonancedenominators quadratic in frequency,or linear?What doesit meanfor modesto be "coupled"?In a measured frequencycharacteristic, when are normalmodes represented by peaks,by dips,by both?What informationis carriedby the phase?In searchingfor normalmodes, what is the differencebetween pulse excitation, white noise excitation, and sinusoidal excitation?Arc thereother options of interest?Do dissipativcsystems have normal modes? [Work supported by NSF.]

9:10

3aMU2. The role of finite-elementanalysis in modestudies of musicalinstruments. Oliver E. Rodgers (Mech. Eng. Dept., Univ. of Delaware, Newark, DE 19711 ) Vibrationanalysis using finite-element methods of themechanical systems of musicalinstruments have been and will continue to bean important and powerful tool for researchand development workers studying musical instruments. If properly planned, executed,and inte•reted, a finite-elementcalculation can describe all of the possiblevibration modes, including some that might bemissed in experimentalstudies because of complicationsin exciting and recording systems. It canbe very useful for making studiesof theeffect of singledesign or tuningvariables on mode-frequency placement. The method is especially valuable when the instrumentunder investigation is made of wood,an extremely variable and unpredictable material. (Knowledge of howto adjust thefrequencies of important modes is veryimportant when assembling and fine-tuning most stringed instruments.) Examples of successfuluse and opportunities for furtheruse will be described.

1805 J. Acoust.Soc. Am., Vol. 94, No. 3, Pt. 2, Sept. 1993 126th Meeting:Acoustical Society of America 1805 9:40

•tMU3. Mechanical w'brafionsand radiation fields of guitars. Matthew Brooke (Paul S. Veneklasen& Associates,1711 16th St., SantaMonica, CA 90404) and BernardRichardson (Univ. of WalesCollege of Cardiff,P.O. Box 913, CardiffCF2 3YB, UK)

Someof the researchundertaken by thoCardiff group to try to establishrelationships between the classical guitar's construc- tion and its acousticaloutput are reviewed.Real instrumentshave been studied using techniques such as holographicinterfer- ometry,and the structuralvibrations and associatedradiation fields have been modeledusing finite-element analysis and boandary-elementmethods. Primitive psychoacoustical tests have established that radiatedfrequency components of plucked notesare importantin recognizingindividual instruments. Large amounts of data, collectedover the years,have clearly dem- onstratedthat there are no simplerelationships between the modal propertiesof instrumentsand their estimated"quality." Similar conclusionshave, of course,been drawn by other workersin this field.Recently, the authorshave concentrated more on determiningthe preciserole playedby individualmodes in couplingthe stringsto the body and in radiatingenergy to the surroundingair; it is feltthat thissort of detailis moreindicative of theinstrument's final acoustical action. These investigations emphasizethe importance of theprecise shapes of modes,particularly in thevicinity of thebridge. A discussionof the ways in whichthe luthiercan fine-tune mode shapes and hence maintain control during instrument manufacture is included.

10:10

ß d•lU4.Modal analyaks of noncircularcylinders and bells. ThomasD. Rossing(Phys. Dept., Northern Illinois Univ., DeKalb, IL 60115) and Uwe J. Hansen (Indiana StateUniv., Terre Haute, IN 47809) ß In ovalcylinders, the familiar vibrational modes of a circularcylinder are split into doublets, one new mode having a node in theregion of greatestcurvature and the other having an antinodethere. Since inoreasing the curvature increases the effective stiffnessand thus raises the speed of bendingwaves, the bending wavelengths are generally longer (and the nodes further apart) in theregion of greatercurvature. This phenomenon is the basis of the "two-tone"phenomenon in ancient Chinese bells. The modesplitting in a varietyof noncircularcylinders and bells, observed by means of holographicinterferometry and experimental modaltesting with impact excitation, is described.By usingtwo mirrors,it ispossible to viewsimultaneously the front, end, and top of a vibratingcylinder in holographicinterferograms.

10.•0

3aMU$. Extensionof medalanalysis techniques: Wind instrumentsand radiatedsound fields. Uwe J. Hansen (Dept. of Phys., IndianaState Univ., Terre Haute, IN 47809) and Ingolf Bork (Physikalisch-TechnischeBundesanstalt, 3300 Braunschweig, Germany) The studyof normal modesof a vtbratingstructure using modal analysis involves the phaserelationship between a large numberof coherentsignal pairs obtainedover a predeterminedgeometrical grid coveringthe structure.From a set of transfer functions,resonance frequencies are obtainedand an animatedpicture of the motionat the resonancefrequency is displayedon a computerscreen. Extending this technique to standingand traveling waves in air involvesusing an excitation source as reference andforming transfer functions between that referencesource and sound pressure level measurements at predetermined locations in the soundfield. The techniquewill be illustratedwith animationsof air modesin a fluteand with animationsof soundfields radiatedby a pianoat severalfrequencies [I. Bork,Acustica 75, 154-167(1991)].

ContributedPapers

11:10 11:25

8aMU6. Brass instrument bell wbrations and coupling to air modes. •!U7. Tracking the dynamics of musical instruments based on a PeterL. Hockje,Colby A. Payne,and David N. Kjar (Dept. of Phys., high-resolutiontime-frequency representation. William J. Pielemeier Univ. of Northern Iowa, Cedar Falls, IA 50614-0150} and Gregory H. Wakefield (EECS Dept., Univ. of Michigan, 1301 Beal Ave., Ann Arbor, MI 48109) The vibrationsof brassinstrument bodies are important to musi- cians.Three proposed mechanisms by whichplayers might detect these Attacks and other phenomenathat involverapid amplitudeand vibrationsare radiation,mechanical coupling to handsand mouth,and frequencyvariations over time present a difficultproblem in the studyof alterationof the acousticresponse of the instrumentbore as felt by the the dynamicsof musicalinstrument modes. Fourier-series-based meth- lips. The first mechanismhas beendemonstrated by other researchers uds provide adequatetime resolution under the conditionsof signal [e.g.,B. Lawsonand W. Lawson,J. Acoust.SOc. Am. 77, 1913-1916 periodicitybut performancedeteriorates rapidly with grossinharmonic- (1985)]. The mechanicalcoupling is strong,but this mechanismhas ity or large amplitude and frequency transients.Short-time Fourier minimal musical significance.For the third mechanism,the coupling transform (STFT) methods are most robust to these variations but between the instrument shell vibrational modes and the crnss-seetional providelimited resolutionin time and frequency.In a previouspaper, modesof the air in the bore is dependenton their relativesymmetries. an alternativetime-frequency representation that achievesbetter reso- In the narrow main bore only plane wavespropagate; in theory these lution than STFT methods,yet remainsrobust to conditionsdegrading shouldcouple only to cylindrica!lysymmetric shell modes.Trombone Fourierseries analysis, was presented [Pielemeier et ai., 1. Acoust.$oc. bell vibrationalmode patterus, identified by holographicinterferometry, Am. 92, 2430(A) (1992)]. The presentpaper develops estimators for exhibit symmetriessimilar to thosein churchbells, with nodal circles modal parametersof musicalinstruments based on this alternativetime- and nodalmeridians. However, they may be indexedby the singlenum- frequencyrepresentation. The performanceof theseestimators is ana- ber m of the nodal meridianplanes. For m > 0, the frequenciesfm are lyzed and comparedwith that of Fourier seriesand STFT methodsfor approximatelydescribed by a simplifiedChladni's law of the form fm severalmusical eases, including the attack transientsof trumpet, vibra- =C(m} p. For a typical trombonebell, C=209 Hz and p=l.l, while phone,and flute notes.In general,it is found that the proposedestima- fo=277 Hz. tors provide a more accurateportrait of the spectraldynamics of the

1806 d. Acoust.Soc. Am., VoL 94, No. 3, Pt. 2, Sept. 1993 126th Meeting:Acoustical Society of Amedca 1806 musicalsignal than is possibleusing estimators based on the othertwo below20 000 Hz, aswell asstress maps of the reedstructure, etc. The representations. simulationis flexibleenough to allow for the inclusionof any typeof ligature,embouchure, air columnpressure spectrum, mouthpiece, and 11:40 variationsin reedmaterial properties and biologyduring any stageof the life cycleof the reed.This allowsfor mostquestions of practical 3aMU8. The perfect clarinet reed? Vibrational modesof realistic importancein reedscience to beexamined (including those of historical clarinetreeds. DonaldCasadonte (Dept. of Music,Ohio StateUniv., reedshapes). Specifically, the problem of reedresonance IS. C. Thomp- Columbus, OH 43210) son, J. Acoust.SOc. Am. 66, 1299-1307 (1979)] is investigated.It is Using resultsobtained from prior investigationsinto the biology, shown that a good reed is one "tuned" to maximize statisticallythe chemistry,and physicsof the clarinet reed [D. Casadonte,J. Acoust. poweroutput from the overtonesof the air column.This tuning is Soc.Am. 90, 2351(A) (1991}], a realisticcomputer simulation using graduallylost as the reedages. Finally, the reverseprocedure of design- the ANSYS finite-elementprogram has been developed. Using this sim- ing a reed shapeand material that will maximizethe resonancefor a ulation,modal frequencies and shapeswere isolatedfor thosemodes typicalclarinet air columnis studied.

WEDNESDAY MORNING, 6 OCTOBER 1993 DENVER ROOM, 8:15 TO 11:45 A.M.

Session 3aNS

Noise: Characterizationof EnvironmentalNoise Impact

HenningE. yon Gierke, Chair 1325Meadow Lane, YellowSprings, Ohio 45387

Chair's lntroduction•8:15

Invited Papers

8:20

3aNSI. Airport noise:The problemand somesolutions and frustrations. Paul F• Tauer (Mayor, City of Aurora, Colorado, 1470 S. Havana, Ste. 808, Aurora, CO 80012)

Citizensof nearbycommunities, usually with little or no directcontrol over airport operations, bear the bruntof airportnoise. Minimal concernfor the impactof this noisehas been shown by the airlines,the airports,and the F.A.A. Politicalpressure and legalaction have both been used in attemptsto forcethe partiesresponsible to addressthe problem.The authorhas worked for severalyears on theseissues in his capacityas former Council Member and current Mayor of a city of 235 000 residentsthat bordersboth the soon-to-closeStapleton Airport and the new Denver InternationalAirport, and as Presidentof the National Organizationto Insurea Sound-controlledEnvironment (NOISE). A significantproject to reducethe impactof airportnoise was the StapletonNoise Insulation Program, which involved the expenditureof $20,000,000to sound-insulatehomes in Aurora,CO. Recentlegislation regarding Stage IIl aircraftwill reducenoise at the source,but doesnot adequatelyaddress noise impact. Thus, politicalconflict, prolonged litigation, and airport-capacitylimitations will continue.There is a solution:communication and cooperation.

8:45

3aNS2. Communityannoyance by aircraft no'se. JamesM. Fields (10407 Royal Rd., SilverSpring, MD 20903)

Rigorouslydesigned social surveys, not publiccomplaint actions, provide the mostdirect availableevidence about the impact of environmentalnoise on residents.The balanceof the availablesocial survey evidence indicates that while personalattitudes affect noiseannoyance, demographic characteristics and ambient noiselevels do not affect annoyancewith audible sounds.A continuouslygraded annoyance reaction to noisedoes not providea strongscientific basis for choosing"highly annoyed"rather than any other degreeof annoyanceas an acceptabilitycriterion. A rigoroussynthesis of annoyancesurvey results must screen out erroneousdata, useobjective methods for selectingdata sets,systematically adjust for importantdifferences in nominalnoise measurementconditions, weight data points by their precision,have a firm empirical basisfor relating diverseannoyance measures,and satisfactorily evaluate the likelyprecision of the resultingsynthesis curve. A theoreticallysound justification for the form of a dichotomousdose/response curve must include a theoryabout the distributionof measuredreactions to noise.Existing dose/responsecurves continue to makeuseful contributions to noisepolicy. Additional work will be neededbefore a synthesisof communitydose/response relationships can be developedthat meetsthe previouslymentioned criteria.

9:10

3oN•. Current statns of sl•p disturbanceres•areh and developmentof a criterion for aircraft noi• •xOosnre. Lawrence S. Finegold (USAF ArmstrongLab., AL/OEBN, 2610 SeventhSt., Wright-PattersonAFB, OH 45433) Therecurrently exists no generallyaccepted criterion for an acceptablelevel of nighttimesleep disturbance from aircraftnoise. Indeed,there is little agreementconcerning the appropriatescientific definition of sleepdisturbance, the appropriatenoise exposuremetric for this environmentaleffect, or the circumstancesunder which such predictionsneed to be includedin

1807 d. Acoust.Soc. Am., VoL 94, No. 3, Pt. 2, Sept. 1993 126th Meeting:Acoustical Society of America 1807 environmentalimpact analyses. However, with the largebody of scientificevidence on sleepdisturbance due to environmental noisethat hasaccumulated over the past20 yr, it is now possibleto promotean interimsleep disturbance curve for usein the federalenvironmental impact analysis process. This presentationfocuses on the resultsof recentresearch and the implicationsfor environmentalpolicy decisions. Both laboratoryand field research,including research in the United Statesand Europe,are addressed.Development of the sleepdisturbance curve incorporated into the 1992report of the FederalInteragency Committee on Noise (FICON) is also reviewed.

9:.35

3aNS4. Assessment of speech interference from aircraft flyover noise in schools and other communication critical environments.Karl Pearsons (BBN Systemsand Technologies,21120 VanowenSt., CanogaPark, CA 91303) Althoughmost assessments of the effectsof communitynoise impacts on peopleconcentrate on annoyance,it is importantin somespeech-critical settings to assessthe degreeto which noiseinterferes with communicationas well. Speechintelli•ibility metricsare helpfulin suchsituations, even though they requiremore detailedinformation about noise exposure than is captured by cumulativemetrics such as the day-night averagesound level (DNL). Alternatemetrics for assessingspeech inteiligibility and their usesand limitationswill be described.Comparisons will be madebetween such metrics and thosecommonly used to assess environmentalnoise effects on a long-termaverage basis.

10.-00

3aNSS. The presentaircraft noiseevaluation process. Louise Maillett (Federal Aviation Admin. Office of Environment and Energy, 800 IndependenceAve., S.W., Washington,DC 20591)

The legal backgroundand policy decisionsunderlying present U.S. Governmentnoise impact assessmentprocedures are outlined.Collaboration and reviewprocesses to satisfythe mandatesof the variousagencies are discussed,with emphasison the FAA's missionand plans regardingaircraft noiseabatement.

10:25

3aNS6, New languageand processesfor examiningenvironmental noise. NicholasP. Miller (Harris, Miller, Miller, & Hanson, Inc., 429 Marrett Rd., Lexington, MA 02173)

Guidelinesand standardshave been developedthat identify the relationshipbetween noise levels and land uses.These relationshipswere intendedto definewhat land useswere "compatible"with specificlevels of noise,but, in doingso, took into considerationnot only publichealth and welfare,but alsosuch concerns as the rightsof propertyowners, available technology, and feasibility.The inclusionof thesebasically economic concerns meant that the noiseand land-usecompatibility guidelines would not necessarilyprotect people from all the adverseeffects of noiseor, perhapsmore important,even identify when and whereadverse effects might occur. This distinctionbetween land-use compatibility and averseeffects on peoplehas generally been lostor overlooked.It is timeto makethis distinction clear. Case histories where pursuing land-use compatibility did notprotect peoplefrom the adverseeffects of noiseor identifythese adverse effects are discussed. A languageand approach are proposed for clearlydifferentiating between the conceptsof !and-usecompatibility and identificationof disruptiveeffects.

10:S0

3aNS7. Suggestionsfor solutions. KennethMcK. Eldred (Ken Eldred Eng., MeadowCove, East Boothbay,ME 04544-0501) Solutionsto someof the problemsthat inhibit effectivefunctioning of the environmentalimpact evaluationprocess are suggested,including approaches for the useof metricsto improvecommunication with the affectedpublic so that quantitative descriptionsof both single-eventand cumulativenoise are more nearlyrelated to the perceptions;development of guidelinesfor the definitionof projectstudy areas to includeall who are anticipatedto experiencesignificant changes, quantification of individualchanges in noise,as well as the net populationsexposed to variouslevels, that addressconcerns within the entirestudy area;and researchto improveour understandingof noiseannoyance and its alleviationand to extendour noisemodeling capabilityto areasfurther from airportsthen presentlypossible.

ContdbutedPapers

11:15 ordinanceis now sharedbetween the city health and policedepart- ments.Because there is no zoningin the City of Houston,this ordinance 3aNS8. The new City of Houston soundregulation ordinance, C. posessome unique challenges; manufacturing facilities, bars, and night- Moritz (Collaboration in Sci. and Technol., Inc., 15835 Park Ten PI., clubs are often located in residential areas. The motivation for this new Ste. 105, Houston, TX 77084-5131) and H. Huey (Councilwoman, ordinanceand recentexperiences with its enforcementwill be discussed. District A, City of Houston, P.O. Box 1562, Houston, TX 77251)

In Januaryof 1993, the City of Houstonadopted a new sound 11:30 regulationordinance. Previous ordinances did not specifyallowable 3aNS9. Designof a large-seaie,in-home study of noise-indueedsleep soundlevels, only that it was unlawful to make loud or excessivenoises. disturbance. Sanford Fidell, Karl Pearsons,Richard Howe (BBN The city healthdepartment had usedvalues of 75 dBA (daytime) and Systemsand Teehnologles,21120 VanowenSt., Canoga Park, CA 65 dBA (nighttime) to determine if noiseswere excessive.The new 91303), and LawrenceFinegold (USAF, Wright-PattersonAFB, ordinanceestablished allowable A-weighted sound levels of 65 dBA OH 45433-6573) (daytime) and 58 dBA (nighttime) on residentialproperty and 68 dBA (day or nighttime) on nonresidentialproperty. Enforcement under this Pearsous,Barber, and Tabachnick(1990) havedocumented large

1808 J. Acoust.Soc. Am., Vol. 94, No. 3, Pt. 2, Sept. 1993 126thMeeting: Acoustical Society of America 1808 differencesin the findingsof laboratoryand home studies of the ability currentlyconducting an in-homestudy of sleepdisturbance, intended in of noiseto disturbsleep. More recently,preliminary analyses of data part to clarify severalissues not fully resolvedin prior work. These collectedin a large-scale,in-home study of sleepdisturbance [Oilerhead includethe definitionof sleepdisturbance and the temporallinkage et al. (1992)] suggesta lowerprobability of awakeningthan indicated betweennoise exposure and sleepdisturbance. The rationale,design, by a dosage-responserelationship recommended by Federal Intera- gencyCommittee on Noise [FICON (1992)]. The U.S. Air Force is and progressof the Air Force studyare described.

WEDNESDAY MORNING, 6 OCTOBER 1993 SILVER ROOM, 8:25 A.M. TO 12:15 P.M.

Session 3aPA

Physical Acousticsand Education in Acoustics:Frontiers of Physical Acoustics

Seth J. Putterman, Chair PhysicsDepartment, University of California,Los Angeles,California 90024

Chair's Introduetion•8:2S

Invited Papers

8:30

3oPAl. Thermoacousticengines. Gregory W. Swift (CondensedMatter and ThermalPhysics Group, Mail StopK764, Los Alamos Natl. Lab., Los Alamos, NM 87545)

Thermoaconsticengines are energy-conversiondevices that achievesimplicity and reliabilityby use of acoustics.Their efficiencycan be a substantialfraction of the Carnot efficiency.In thermoacousticprime movers,heat flow from a high- temperaturesource to a low-temperaturesink generatesacoustic power. In thermoaconsticrefrigerators, acotrstic power is used to pumpheat from a low-temperaturesource to a high-temperaturesink. Applications of thermoacousticsunder development at severalinstitutions will be shown,possibility including refrigeration, sonar, cryogen liquefaction, and electric-powergeneration. Fundamentalprinciples of thermoacoustieswill be reviewed,and assumptions underlying our present(linear) understandingwill bediscussed. Limitations of our presentunderstanding will be outlined,and their implications for designof practicaldevices will be discussed.

9.-00

3sPA2. Helioseismology:Listening to the insideof the sun. Jurl Toomre (JILA, Univ. of Colorado,Boulder, CO 80309)

The sun is oscillatingin an intricatethough gentle manner. The patternsof motionobserved in the solaratmosphere are complicated,for they result from interference between about 10 ? resonant modes of oscillationof theinterior. The sun possesses bothacoustic p modes,for whichpressure is the restoringforce, and gravityg modes,for whichbuoyancy is the dominantforce. Each resonantmode resides in a cavitybeneath the solarsurface, the depthof which dependsboth on the type of modeand on its geometry.Some cavities are quite shallow,whereas others extend to the very centerof the star. Sincethe frequenciesof the modesare determinedby the stratificationand dynamicsof the portion of the sun where their amplitudesare appreciable, accuratedetermination of the frequenciesby observationsaffords remarkable ways of probingthe insideof the star. During the pastdecade there has been significant progress in bothobservation and theory. The unravellingof informationfrom many modes formsthe basisof the subjectcalled helioseismology. It promisesstudy of the insideof the sun in sufficientdetail to test the premisesof stellarstructure theory, and thushas implications for muchof astrophysics.It canalso provide crucial information aboutthe temperatureand massdistribution within the sunfor testingissues in particlephysics and theoriesof gravitation.

9:30

3sPA3. Physicalacoustics at 500 GHz: 31 octavesabove middle C. Humphrey J. Marls (Dept. of Phys., Brown Univ., Providence, RI 02912)

Experimentsare describedin whichthe techniquesof picosecondoptics are usedto generateand detectultrasonic waves at frequenciesas high as 500 GHz. The methodalso provides exceptionally good spatial and temporalresolution, thereby making possiblepulse-echo acoustic measurements on a broadrange of nanostrueturesof currenttechnical interest. Examples will be givenof resultsthat havebeen obtained by thisapproach, and possiblefuture developments will be discussed.

10.'00-10:15 Break

10:15

3sPA4. •ynchronot•s picosecondsonolumine•ccn•'•. Bradley P, Barber, Robert gliller, Ritva Lof•t•dt, and Seth Putterman {Phys. Dept., Univ. of California,Los Angeles,CA 90024} A strongsound field can (I) trap a bubbleof gasat a velocitynode, (2} maintainthe bubbleagainst diffusioh, and (3} at sufficientintensity cause it to emit flashesof light that haveintensities over 30 mW and widthsless than 50 ps. The flashesare emitted in a clocklikefashion with a jitter that is also lessthan 50 ps. The spectralintensity of the sonoluminescence(SL)

1809 J. Acoust.Soc. Am., Vol. 94, No. 3, Pt. 2, Sept. 1993 126th Meeting:Acoustical Society of America 1809 increasesinto the ultraviolet.The mechanismfor thiseffect is still unknownbut light scatteringexperiments have resolved the bubblemotion--radius versus time--on a scaleof nanosecondsand indicate that the lightis emittedby a supersoniccollapse. The emittedintensity is a strongfunction of ambienttemperature and varies by a factorof 200between I and40 C. Lightscattering measurementsof temperature-dependent SL therefore provide data that can critically test any proposed theory such as imploding shockwaves [C. C. Wu and P. H. Roberts,Phys. Rev. Lett. (May 1993)]. [Work supportedby the US DOE Divisionof AdvancedEnergy Projects, R. L. is supportedby an AT&T fellowship.]

3sPAS. Evolutionof the scanningmicroscopes both for imagingand lithography. C. F. Quate (Edward L. Ginzton Lab., Stanford Univ., Standard, CA 94205)

In recenttimes the atomicforce microscope and other scanning probes have emerged as formidable instruments for imaging insulatingsurfaces. They can be operatedin air, in liquid, and in vacuumand they have had an impact in the fieldsof electrochemistryand in cellularbiology. Here, focuswill be on solidsurfaces where the AFM hasbeen successfully used to image a varietyof surfacesthat are difficultto studywith the opticaland electronmicroscopes. Topography and microroughnessof siliconwafers will be usedto illustratethe utility of this instrument.Surface modification on the atomicscale has been demon- stratedfor a varietyof systems.In a secondapplication the force microscope has been combined with other forms of microscopes. The combinationprovides the operationwith a simplemeans of controllingthe spacingbetween tip and samplethroughout the scanningcycle. This principleis illustratedwith a descriptionof the near-fieldoptical microscope as combinedwith the force mieroseope.This combinationallows one to scanwith the tip space5 nm from the sample.

11:15

$aPA6. Quantitative ultrasonic imaging for tissue characterization. JamesG. Miller, Samuel A. Wickline, Julio E. Perez, Benieo Barzilai, Mark R. Holland, Scott M. Handley, and Burton E. Sobel (Dept. of Phys. and CardiovascularDiv., WashingtonUniv., St. Louis,MO 63130} This presentationwill illustraterelationships between physical acoustics and ultrasonicimaging for medicaldiagnosis. Ul- trasonictissue characterization is designedto complementtwo-dimensional echocardiography by providinginformation in additionto that derivedfrom an assessmentof tissuedimension and motion.The hypothesisis that indicesbased on (frequency- dependent)backscatter and attenuationcan providea noninvasivetool for the early diagnosisof diversedisease processes includingischemia and cardiomyopathy.Differentiation between mature infarct and acutelyischemic myocardium, which might benefitfrom reperfusionby angioplastyor thrombolysis,appears to be feasibleon the basisof the frequencydependence of backscatter,which is lowerin zonesof infarctthan in acutelyischemic or normalmyocardium. Two-dimensional images are formedfrom scansmade with the directionof propagationof ultrasoundat varyingangles relative to the localfiber orientation of the myocardium.Backscatter and attenuationvary substantiallywith the angleof insonificationrelative to myofibers.This researchis designedto lay the groundworkfor exploitingthe anisotropyof myocardialultrasonic properties to achieveimproved understandingof cardiacmechanical properties (elasticity and compliance)in normaland diseasedhearts. [Work supportedby NIH HL40302, HL17646, HL42950.]

ContributedPapers

11:45 broadbandto narrow-bandnoise during the transientperiod. These light emissionsand acousticemissions will be presentedand possible 3sPA7. Some light emission features of single bubble correlationdiscussed. [Work supportedby ONR.] aonolumineseence. Scan M. Cordry (Dept. of Phys., Univ. of Mississippi,University, MS 38677), LawrenceA. Crum, and Ronald 12:00 A. Roy (Universityof Washington,Seattle, WA 98105} 3aPA8. Similitudein thermnaeousties.Jeffrey R. Olsonand Gregory Bubblescreated via electrolysiswere allowed to risethough water in W. Swift (CondensedMatter and Thermal PhysicsGroup, Los a quiet acousticlevitation vessel. The soundfield was then activated, Alamos Natl. Lab., Los Alamos, NM 87545) forcingseveral bubbles to convergeand coalescenear a pressureantin- ode. Light emissionmeasurements were then takenwith a Hamamatsu The principleof similitudehas been appliedto thermoacoustics. photomultipliertube and singlephoton counteras a state of single Usingsimilitude reduces the numberof variablesnecessary to describe bubble sonoluminescence(SBSL) evolved. The measurements reveal an experiment,which can greatlyreduce experimentation time. In ad- brief periodsfluctuations in light emissionintensity followed by long dition, it providesinsight into the buildingof modelswith identical periodsof stable(i.e., nonfluctuating)emission. The time scalesfor the performancecharacteristics. Such models would duplicate even unan- fluctuations are on the order of half a second. Previous measurements of ticipatednonlinear behavior. Th•s allowsone to build testprototypes light emissionhave indicatedthat SBSL exhibits remarkably long-lived, that operate at conditions whigh arc more caaily accessiblethan the stable behavior [Gaitan et aL, J. Acoust. Soc. Am. 91, 3166 (1992); B. desiredfinal product.For example,a prototypethat operatesat modest P. Barber and S. J. Putterman, Nature 352, 318 (1991)]. These mea- pressuresusing heavy gas such as argoncould model equipment that is surements,however, imply a transientregime that the bubblemust pass intended to operate at high pressureusing light gas such as helium. through while seekinga final positionof stability. The highestlight Similitudehas been verified using a largethermoacoustic engine oper- emissionintensities are seenin the transientregime. These transient atingwith helium,neon, and argon,and hasbeen found to be obeyed light emissionshould provide important information concerningthe almostperfectly, even for nonlineareffects whose origin is not under- mechanismsthrough which SBSL developsits remarkable stability. stood.Therefore it is believedthis principlecan be appliedto make Further, acoustic emissionsfrom SBSL were observed to evolve from meaningfulpredictions using simpler, cheaper test models.

1810 J. Acoust.Soc. Am., VoL 94, No. 3, Pt. 2, Sept. 1993 126th Meeting:Acoustical Society of America 1810 WEDNESDAY MORNING, 6 OCTOBER 1993 VAIL ROOM, 8:25 A.M. TO 12:00 NOON

Session 3aPP

Psychologicaland PhysiologicalAcoustics: Cochlear Physiology, Hearing Impairment, and•Measurement of Auditory Function

JaneOpie, Chair PsychoacousticsLaboratory, Department of Speechand HearingScience, Arizona State University, Tempe, Arizona 85287

C'nalr's Introduction--8:25

ContributedPapers

8:30 Marjorie R. Leek (Army Audiol. and SpeechCtr., Walter ReedArmy Med. Ctr., Washington, DC 20307-5001) 3aPP1. Direct evidence for automatic gain control in the cochlea. J. J. Zwislockiand M. Chatterjee (Inst. for SensoryRes. and Dept. of Abnormal frequencyresolution associated with sensorinenralhear- Bioeng. and Neurosci., SyracuseUniv., Syracuse,N¾ 13244-5290} ing impairmentproduces a smearingof spectraldetail in the internal representationof complexacoustic stimuli. As a result, listenerswith Compressionof the input/outputfunctions of auditorynerve fibers hearingloss may have difficultylocating spectral peaks that provide wasascribed to automaticgain control by Roseand his associates many importantcues to speechunderstanding. This studyexamined the rela- yearsago. It was ascribedto synapticprocesses [C. D. Geislerand S. tionshipbetween frequency separation of peaksin a complexsound and Greenberg,J. Acoust.Soc. Am. 80, 1352-1363(1986)]. But compres- the degreeof spectralcontrast preserved in normaland impairedaudi- sion is known to take place in the cochlea,as has beendocumented at tory systems.Five hearing-impairedsubjects (HI) and five normal- the basilar membraneand hair cell levels. By comparingmeasured hearingsubjects { NH) discriminateda fiat-spectrum bandpass stimulus waveformdistortion and the sizeof the secondharmonic to thosepre- from a stimuluscontaining a sinusoidalripple acrossits frequency dictedfrom the input/output functionsof Hensen'scells, it is demon- range.The peak-to-valleyamplitude (in dB) necessaryfor detectionof stratedthat the cochlear compression is due to automaticgain control at the ripple was measuredfor ripple frequenciesranging from I to 9 leastup to a soundpressure level of 70 dB in Mongoliangerbils. Strong cycles/oct.Auditory filter characteristicsin notched-noisewere mea- compressionhas been found at levelsas low as 20 dB SPL. Since the suredat ! and 3 kHz in orderto assessthe relationshipbetween fre- responsemagnitude of Hensen'scells has beenshown by the present quencyresolution and the ability to detectspectral contrast in complex authorsand othersto be directlyproportional to that of the outer hair spectra.There wereclear differences between groups in both auditory cells,this demonstrationshould be applicableto the hair cellsthem- filter characteristicsand spectralcontrast detection. Auditory filters selves.The almostcomplete lack of waveformdistortion was present tendedto be both broaderand more asymmetricfor HI listenersthan independentof frequencydistance from CF and could not have been forNH listeners.Mean ripple amplitudes at threshold were approxi- causedby spectralfiltering. [Work supportedby NIDCD Grant No. mately 4 dB lower for the NH group than the HI group at all ripple DC00074.] frequencies.However, excitation patterns based on auditory filter char- acteristicsand thresholdstimuli specificto individuallisteners exhibited 8:45 levelsof peak-to-valleycontrast that were nearly identicalacross listen- ers. This suggeststhat increasedripple detection thresholdsof the 3aPP2. Intracellular transfer functions in the apieal cochlear turn: hearing-impairedlisteners were due to spectralsmearing resulting from Implications for the pitch code. Monita Chatterice and Jozef J. impairedfrequency resolution. [Work supportedby NIDCD Grant No. Zwislocki (Inst. for Sensory Res., Merrill Ln., SyracuseUniv., DC00626.] Syracuse,NY 13244-5290)

lntra- and extracellular ac transfer functions were recorded in the 500-Hz to I-kHz regionof the Mongoliangerbil cochlea. In agreement 9:15 with previousresults obtained in the 2-kHz location,the bestfrequency 3aPP4. Formant transition discrimination at varying frequency decreasedwith increasingSPL, the shiftranging from !/2 to 1 oct.The regionsamong normal hearing youngand elderly adults as a function phasetransfer function also exhibiteda shift from low to high SPLs of noise,frequency region, and transitiondirection. Jane F. MacNell amountingto about 180 deg. Damageto the preparationresulted in (Dept. of Psychol.,Univ. of Calgary, 2500 University Dr., N. W., smallerresponses, lowered EP, a reductionin the peakshift, as well as Calgary, AB T2N IN4, Canada) a disappearanceof the phaseshift at high SPLs. The normal transfer functionsdemonstrate a conspicuoushigh-frequency notch and second- This study investigatedthe perceptualabilities of young (18-28 ary maximumat moderateand higher intensities.The findingthat, in years) and elderly (65-75 years}adults to discriminatesuprathreshold the rangebetween 500 Hz and 2.5 kHz, the BF is intensity-dependent, short duration dynamic frequencytransitions. Influences of frequency indicatesthat the placeof maximumexcitation cannot be an adequate region ( i to 3 kHz), transitiondirection (upward or downwardglid- code for pitch. It has beensuggested previously with respectto the ing), offsetfrequencies (converging or diverging),and background con- 2-kHz location,that the one intensity-independentfeature of the trans- dition (quiet or noise) were examined.Signals were 60-mstransitions fer functionsis the high-frequencycutoff. This seemsto be approxi- classifiedaccording to whether or not: they divergedto differingoffset matelytrue for the apicalturn of the gerbilalso. [Work supportedby frequencies,converged on a common terminal frequency;and had an NIDCD.] upwardor downwardtrajectory. Young adultsdisplayed smaller just- noticeable differences (jnds) relative to the elderly, and the elderly

9.'00 showedgreater effects for frequencyregion, noise, and transitiondirec- tion. Signalscentered at 3 kHz were considerablymore difficult for the 3aPP3. The influence of frequency resolution on the detection of elderly to distinguisheven though hearingsensitivity levels were com- spectralcontrast by hearing-impairedlistenera. Van Summersand parableacross both groupsat this region.However, amongboth age

1811 J. Acoust.Soc. Am., Vol. 94, No. 3, Pt. 2, Sept. 1993 126th Meeting:Acoustical Society of America 1811 groupsdiverging signals produced smaller jnds than did converging cues.One thereforeexpects that individualswith high-frequencyhear- signals.The resultsof the study showedthat elderly subjectswith com- ing losswill fail at elevationtasks, though they might succeedat FOB parableaudiological profiles to youngadults, or a mild sensorineural tasks.Listeners with bilateral sensorineuralhearing loss, moderate in hearingloss, have greaterdifficulty distinguishing dynamic sounds, es- the speechrange and severeat high frequencies,were given source peciallyin backgroundnoise. identificationtasks in both elevation(three sourcesspanning 30 deg) and FOB geometries.The stimuli were white noisebursts, ranging in

9:30 level from 42 to 90 dB SPL. A controlexperiment showed that the listenerscould successfullyidentify sourcesin the left-overhead-right 3aPPS. Stream segregationin normal-hearingand cochlear-impaired plane.Results for the sagittalplane showed that all listenersperformed listeners. 3. H. Grose, J. W. Hall, and L. Mendoza (Div. significantlyless well than normalcontrols. In the FOB task, perfor- Otolaryngol./Head & Neck Surgery, Univ. North Carolina, Chapel mancewas well abovechance, though listeners characteristically lacked Hill, NC 27599-7070) either a front sensation or else a back sensation. In the elevation task, performancewas, with a few exceptions,near chancefor all listeners Cueblear-impairedand normal-hearinglisteners were comparedon and all levels.[Work supportedby the NIDCD, DC00181.] two tasksintended to assessauditory stream segregation. One taskmea- suredgap discriminationbetween two tonesthat werepresented either in isolationor were embeddedinto a sequentialstream of tones.For 10-.30 tonepairs distally spaced in frequency,performance was poor when the toneswere presentedin isolationbut improvedwhen they were drawn 3aPPS. Vowel discrimination after multichannel compression. E. into separateauditory streams, presumably because temporal judgments William Yund and Thomas R. Crain (VA Med. Ctr., 150 Muir Rd., could now be made within a stream. Both groupsof listenersgave Martinez, CA 94553) similarpatterns of resultsalthough some differences were apparent. The The effectof full-rangemultichannel compression (MCC) on vowel secondtask was a melodyrecognition procedure [J. A. P.M. de Laat discrimination was studied in hearing-impairedand normal-hearing andR. Plump,]. Acoust.Soc. Am. 78, 1574-1577(1985)] and involved subjects.For normal-hearingsubjects MCC wasfit to four hypothetical identifyinga 4-note target melody embeddedbetween two competing fiat losses,with thresholdsranging from 60 to 90 dB SPL, and one melodiesas a functionof the proximityand temporalsynchrony of the hypotheticalsloped loss, with thresholdsnormal at 500 Hz and 90 dB competingmelodies. In bothgroups, marked individual differences were observed. Results from both tasks will be discussed in terms of the SPL at 4 kHz. Each hearing-impairedsubject was testedwith the fiat MCC systemsas well as one fit to thesubject's own hearing loss profile. effectsof cochlearimpairment on auditorygrouping skills. [Work sup- Compressionratios variedfrom 1.75 to 7.00, in the flat MCC, and the portedby the NIDCD R01-DC01507.] numberof channelsvaried from 2 to 31. Robinson-Hantingtoncom- pression[C. E. Robinsonand D. A. Huntington,J. Acoust.Sue. Am. 9:45 •4, 314 (1973)] hada 10-mstime window in all channels.Unprocessed stimuliand frequency-equalizedlinear amplificationwere controlcon- 3aPP6. Modulation detection interference in subjects with a mild, ditions. The expecteddeleterious effects of MCC on vowel discrimina- high-frequencyhearing loss. Jane M. Opic and Sid P. Bacon tion are clear for the most severecompression systems, but preliminary (Psyehoacoust.Lab., Dept. of Speechand Hear. Sei., Arizona State resultsindicate that they fall off rapidly as the numberof channelsand Univ., Tempe, AZ 85287-1908) compressionratios decrease. Complete results and their implicationsfor Modulation detection interference (MDI) was measured in three the applicationof MCC in hearingaids will be discussed.[Work sup- normal-bearingsubjects and in threesubjects with mild, high-frequency portedby Departmentof VeteransAffairs.] sensorineuralhearing impairment. Subjects detected 10-Hz amplitude modulationof a signalcarrier in quietand in the presenceof a masker carrierthat wasunmodulated or amplitudemodulated (depth of 10o%} 10:45 from 2 to 40 Hz. The carrier frequencieswere 984 and 3952 Hz; either 3aPP9. The roles of parametric demodulation, rectifying couldserve as the masker,while the otherserved as the signal.Thus, for demodulation, and coherent demodulation in human the hearing-impairedsubjects, one eartier wasin the regionof hearing amplitude-modulatedultrasonic hearing. SbengkeZeng and Richard loss.In experimentI, both the signaland maskerwere presentedat B. Beard (Biomed.Eng. and Sci.Inst., Drexel Univ., Philadelphia,PA equalsound pressure levels (SPLs). In experiment2, the effectof sen- 19104) sation level (SL) was considered.In both experiments,there was gen- erally little differencebetween the two groupswhen the signal eartier The frequencypattern of the humanauditory sensation in response wasin a regionof normalhearing. However, the hearing-impairedsub- to amplitude-modulated{AM) ultrasonicstimulation is observedto be jects demonstratedmore MDI than did the normal-hearingsubjects proportionalto the frequencyspectrum of the squareof the modulation when the signalwas presentedwithin the regionof hearingloss. This functions[Zeng and Beard,J. Acoust.SOc. Am. 93, 2332 (A} (1993)]. suggeststhat evenmildly hearing-impairedsubjects may havedifficulty In contrast,the frequencypattern of rectifyingdemodulation is propor- processingcomplex, time-varying stimuli. Further, it appearsthat this tional to the frequencyspectrum of the absolutevalues of the modula- may not be solely attributableto audibility but may be mediatedby tion functions;and the frequencypattern of coherentdemodulation is other factors.[Work supportedby NIDCD.] the spectrumof the modulationfunctions. The distinctdiscrepancies in frequencypatterns between the auditorysensation in humanultrasonic 10:00-10:15 Break hearingand the abovetwo physicaldemodulations indicate that recti- fying demodulationand coherentdemodulation are irrelevant to human ultrasonichearing. When the human subject'scooblear region is stim- 10:15 ulatedby an AM ultrasonicmode ( 1+cos 2•rFt)cos2rrft, the subject 3aPP7. Localization uf soundsources in the mediansagittal plane by can sensethe fundamentalmodulation frequency F and the weaker listenerswith high-frequencyhearing loss. Timothy J. Vander Velde, secondharmonic 2F, wheref is the carrierfrequency. The amplitude Brad Rakerd (Dept. of Audiol. and SpeechSei., Michigan StateUniv., ratio of the intensitythreshold for sensingthe firstharmonic to that for EastLansing, MI 48824), and William Morris Hartmann (Michigan sensingthe secondharmonic is 0.37 at F= 1 kHz, 0.57 at 250 Hz, and StateUniv., East Lansing,MI 48824) 0.68 at 3 kHz. Comparedwith the sameratio in parametricdemodula- tion, whichis 0.9, and in the demodulationcaused by the quadratic Sourcesin the mediansagittal plane are localizedon the basisof property,which is 0.25, parametricdemodulation is consideredto have spectral cues. The elevation of sourcestoward the front is determined a joint influencein conjunctionwith the quadraticproperty on human from cuesat high frequency(7 kHz and above). The distinctionbe- AM ultrasonichearing [Zeng, Ph.D. dissertation,Drexel Univ. (1993)]. tweenfront, overhead,and back (FOB} potentiallyinvolves broadband [Work partiallysupported by E!ectro-StimCorp.]

1812 d. Acoust.Soc. Am., VoL 94, No. 3, Pt. 2, Sept. 1993 126thMeeting: Acoustical Society of America 1812 11..00 Effectsof click repetitionrates on acousticreflex thresholdswere investigatedin 11female subjects (total 22 ears)within the age-rangeof 3aPP10. Effects of repetition rate, phase, and sex on the auditory 20 to 26 years.Acoustic reflexes were elicited in responseto ipsilatera] braga.stemresponse 'n normalhearing subjects. T. K. Parthasarathy (Dept. of Speech PathoL and Audiol., Southern Illinois Univ., condensationclicks of 100-•s durationat repetitionrates of 50, 100, Edwardsville, IL 62026 and Central Inst. for the Deaf, St. Louis, MO 150,200, 250,and 300/s.The probetone frequency was 226 Hz andthe 63110) intensitywas 85 dB SPL. Acousticreflex thresholds were defined at the lowestintensity at which a minimumof 0.02-ml changein admittance The effectsof clickrepetition rate and phase on waveI andV latency was evidenton at leasttwo of three trials.The thresholdsbecame sig- of the auditorybrain-stem response (ABR) wereevaluated in ten male nificantlybetter with increasein the repetitionrates. The average and femalenormal hearing subjects. Clicks were presented monaurally thresholdadvantage for the 300/s-clickrate overthe 50/s rate was22.5 via an insertearphone at 70 dB nHL, usingeither a condensation(C), a rarefaction(R), or a alternating(Alt) stimuli at two rates, 11.1 and dB and that of the 100/s rate over the 50/s rate was 12.5dB. Although 61. l/s. Femaleshad shorterabsolute (V) and interpeaklatencies (I-V) suchadvantage with increasein stimulusrepetition rates has been most than the males.These sex-relatedlatency differenceswere phaseinde- commonlyreferred to as temporalintegration, a more appropriateterm pendent. Furthermore, the stimulus phase effect on ABR latencies (I for this phenomenonmay be rate integration.Since the firing ratesof and V) were insignificant.Increasing the repetition rate produced auditory neuronsare known to increasewith increasein stimulusinten- greaterwave I and V latencyshifts for C and Alt clicks than the R sity, it is conceivablethat stimuli presentedat higherrepetition rates are clicks. Resultsseem to suggestsignificant rate-phase interaction effects perceivedas being louder. [Work supportedby BloomsburgUniversity on ABR latencies(I and V). However, the phase-sexand the rate-sex Grants for Researchand CreativeProjects and StateSystem of Higher interactioneffects on ABR latencies(! and V) were insignificant. EducationMinority Faculty DevelopmentFund, Pennsylvania.]

11:15

3aPPII. Effect of click-repetitionrate on acousticreflex growth. 11:45 Vishakha W. Rawonl (Commun. Disord. & Special Educ., 3aPPI3. Effectsof vigilanceon corticalprocessing. D.M. Daly (Box BloomsburgUniv., Bloomsburg,PA 17815) 210855, Dallas, TX 75211 ) Effectsof click-repetitionrate on acousticreflex growth were studied in I 1 youngfemale subjects (total 22 cars). The probetone frequency Normal personssignificantly deprived of sleepshow impaired vigi- was 226 Hz and the intensitywas 85 dB SPL. Followingthe determi- lancewith slowingof motor responses,errors in cognitiveprocessing, nationof ipsilateralacoustic reflex thresholds in responseto condensa- and defectsin recall. Pupillometry measuresautonomic correlates of tion clicksat repetitionrate of 50, 100, 150, 200, 250 and 300/s, reflex vigilance.Effects of sustainedand of fluctuatingvigilance on cortical amplitudeswere measuredat levels5 and 10 dB abovethe thresholds. For each of the measurements data were obtained across three trials. In processingusing standard sets of syntheticacoustic stimuli are reported. 10 of the ears evaluated,data were alsoobtained at 95 dB peSPL for [Daly eta!., J. Neurophysiol.44(1), 200-222 (1980)]. A 60-yr-old eachof the repetitionrate that revealedthat acousticreflex amplitudes womanhad lifelongdifficulty awakening, and if not awakenedmight increasewith increasein repetitionrates. A significanteffect of repeti- sleep14 h continuously.A single7 am 30-ragdose of methylphenidate tion rate and sensationlevel and a significantinteraction was apparent aided arousal; once awake she could remain alert. In 2-h sessionsof for the amplitudesobtained at 5- and 10-dBsensation level (SL}. For unmedicatedcontinuous testing she classified stimuli consistently [p(x 2 all the repetitionrates 10 dB SL yieldedhigher amplitudes than those > G2)0.0001]and appropriately(pO.001, re: 32 normaladults). Her obtainedat 5 dB SL exceptat the 50/s rate whereincrease in sensation performanceafter1 « h wasas consistent asthe best controls. A 54-yr- level did not produceany significantincrease in amplitudes.Detailed old man had sinceadolescence slept less than 3 h per night (typically analyseswill be presentedand the resultswill be discussedwith refer- 2-5 pro). Unlike other reportedphilagrypniacs, for 30 yr he has also enceto rateintegration in theacoustic reflex pathway. [Work supported nappedfor an hour in late morning.Despite diminished sleep require- by BloomsburgUniversity Grants for Researchand CreativeProjects ments, he does not remain alert while awake. Performance with FM and StateSystem of Higher EducationMinority Faculty Development transientsin CVs fluctuatedwidely (p<0.01 to p<0.0001), but re- Fund, Pennsylvania.] mainedconsistent with relativelyCF vowels(p <0.0001). His perfor- manceimproved temporarily with caffeinated(but not decaffeinated) 11:30 coffee.These results are consistentwith evidencethat vigilancemodu- 3aPPI2. Rate integration in click-evoked acoustic reflex thresholds. lates cortical auditory processing;they suggestthat like capacityfor Vishakha W. Rawcol (Commun. Disord. & Special Educ., sleep,individual capacity to remainalert may alsovary in a Gaussian BloomsburgUniv., Bloomsburg,PA 17815} distribution.

1813 J. Acoust. Soc. Am., Vol. 94, No. 3, Pt. 2, Sept. 1993 126th Meeting: AcousticalSociety of America 1813 WEDNESDAY MORNING, 6 OCTOBER 1993 CENTURY ROOM, 8:00 A.M. TO 12:30 P.M.

Session 3aSA

Structural Acoustics and Vibration: Inhomogeneous Structures and Active Control

Jerry H. Ginsberg,Cochair Schoolof MechanicalEngineering, Georgia Institute of Technology,Atlanta, Georgia30332

Chris R. Fuller, Cochair Departmentof MechanicalEngineering, Virginia Polytechnic Institute and State University,Blacksburg, Virginia 24061

Chalr's Introduction--8:00

Invited Paper

8.•5

3aSAI. Reciprocity theorem for oscillationsof inhomogeneouselastic structuresin a Hquid---Modified reciprocity theorem and applications.Leonid M. Lyamshev (N. N. AndreevAcoustical Institute, Shvernik str. 4, 117036Moscow, Russia) The oscillatoryvibrations of inhomogeneouselastic structures are considered.In particular,two problemsinvolving plates and shellswith attachedribs excitedby forcesand momentsare discussed.The formulationuses the Green'sfunction for the wave equationof soundpropagation in a liquid,and the equationsof motionof platesand shellscoupled with thoseof flexuraland torsionalvibrations of ribs. An integral relationshipconnecting the solutionsof two serf-conjugatedboundary problems of inhomogeneousplates and shellsoscillations theory is obtained.This relationshipis the reciprocitytheorem that is a precise mathematicalformulation of the well-knownRayleigh reciprocity principle for oscillatingmechanical systems. If a liquid is movingand thereis a shearflow outsideor insideof a shell (plate} then this relationshipis the modifiedreciprocity theorem for inhomogeneouselastic structures oscillations in a flow that is the generalizationof the Rayleighprinciple. Applications of the reciprocitytheorems are discussed.Flexural wavesreflection, scattering, and radiation by elastic ribs in plates are considered. Nonspecularreflections and resonancephenomena are observed.These are similarto nonspecularreflection, sound scattering, and radiationby elasticbodies in a liquid and are connectedwith interactionsof flexuralwaves in a plate with flexuraland rotational waves in fibs.

ContributedPapers

8'.30 In a complexstructure in whichthe substructuresare fairly periodic thephenomenon of localization(5 la Anderson)and delocalizafion may 3aSA2. Approximate traveling wave solution for impulsively arisewhen the periodicityis disturbed.In this paper, the localization perturbedcircular membrane. Alan Powell (Dept. of Mech. Eng., and alelocalizationthat may manifest in the responseof a beaded (taut } Univ. of Houston, Houston, TX 77204-4792) string are discussed.It is arguedthat this phenomenonis related to the It is instructive to transform the normal modes solution for a circu- phenomenonof passand stop bands that arise in a beadedstring in lax membrane(radius R) suddenlydisphced f0 at the boundaryinto an which baysare fairly identical.A bay is the portionof a stringbetween approximatepurely periodic traveling waveform • = adjacentbeads. When the identityof the baysis disturbed,localization X.4, r/f•-•cos[(n-- •}•r(r/R •- ct/R) -- •r/4], wherec=wave speed and delocalizationoccur at frequenciesthat lie in passand stopbands, (althoughstrictly good for n•, 1, r/R • 1). The seriesevidently has pe- respectively.The disturbancemay be in the form of changingfraction- riod T=8R/c. Individual mode periods T/3,T/7, T/11 .... accountfor ally and randomlythe spatialextents of the hays.Both localizationand the notablecharacteristic symmetry of the waveformabout the centerof alelocalizationmay play a significantrole in the responsebehavior of the periodsT and asymmetryabout the quarterpoints. The --•r/2 focal periodicstructures. phaseshift (finite Hilbert transform)and the simplesign reversal ( shift) at the boundaryare readily deduced.The resultalso appliesto idealsupersonic jets, •z• pressureperturbation, ct• (axial distance) 9:00 M•-- 1.For cell length (axial period) one may take s•t = 8R•M 2-- 1 3aSA4. Vibration damping of large structures induced by attached forthe series, orsp = ]R• 1for the first term. The two-dimensional areall resonant s•uetureg. •1. gtraaber8 and D. l•½it (David Taylor casets unambiguoussst=4(semiwidth) M•f-•--'•. Of course,the exact Res. Ctr., Bethesda,MD 20084-5000) solutionisnot .pe4fiodie atall, the major discrepancy beingin first term approximation(] vs 1.307...),so a betterapproximation is to transform It is well known that the observedvibratory behavior of large and just terms n>2: the characteristicpatiodie waveform wmains a domi- complicatedstructures usually indicates much more damping than can nant feature. be accountedfor by the inherentdissipation in the structuralmaterial. Severalinvestigators have pointed out that greatlyincreased damping may result from vibratory power dissipatedby the numeroussmall resonantsubstructures usually attached to the largemain structure;C. Soizecalled them the "structuralfuzzy" [J. Acoust.Soc. Am. 92, 2365 3aSA3. Localization and deloealizafion in the responseof a beaded (A) ( 1992)].This paperpresents a simplifiedprocedure for estimating string. G. Maidanik and J. Dickey (CDNSWC, Bethesda, MD the effect of these substructureswhen they have many resonancesat 20O84-500) frequenciesnear the excitationfrequency. In this case,the increased

1814 J. Acoust.Soc. Am., Vol. 94, No. 3, Pt.2, Sept.1993 126thMeeting: Acoustical Society of America 1814 dampingof the largestructure depends mainly on the total effective alongthe lengthof the plate.The functionalform of thisdistribution is massof all the substructuresresonating within a frequencyband (say a describedusing a spectralFourier series. whose ascending orders rep- half-octave)centered at the excitationfrequency, and is relativelyinde- resentsuccessive stages in refinementof the scaleto which a model pendentof the specificamount of dissipationin the individualsubstroc- describesinertial effects. The excitationapplied to the plate is takenas tures. The effect of the substructureson the frequencyresponse and a concentrated harmonic force. With the excitation held fixed, the in- vibrationpattern of the main structurecan also be accountedfor in flueneeof eachspectral component of inertialdistribution on the surface simplefashion. The influenceof nonuniformspatial distributions of the responseand radiatedpower are assessed.Evaluations carried out for a attachedsubstrates on the estimatesis alsodiscussed in termsof specific rangeof frequenciesshed light on how smallscale inertial hetcrogene- examples.[Work suppoRedby ONR.] itiescan influencemacroscopic radiation features.

9:15 10:00

3aSAS. Application of the Wiener-Hopf technique to the scattering 3aSA8. The exterior acousticmodes of structures. Notlie Curry and of structural acoustic waves from discontinuities in fluid-loaded Kenneth A. Cunefare (The George W. Woodruff Schoolof Mech. cylindricalshells. StevenL. Means (Graduate Programin Acoust., Eng., GeorgiaInst. of Technol.,Atlanta, GA 30332-0405) Appl. Sei. Bldg., PennState Univ., UniversityPark, PA 16801) The useof a modal-styleapproach for the analysisof the exterior Severaltypes of structuralacoustic waves are knownto propagate radiation characteristicsof structurescontinues to receiveincreasing on fluid-loadedcylindrical shells. When propagatingin the axial direc- attention.This approachgenerally seeks to find a set of orthogonal tion they can be describedby a dispersionrelation D(kx,o•)=0. When functions,or acousticmodes, that diagonalizea radiationoperator in thesewaves are incidenton a shelldiscontinuity, here considered larger the exterior domain of an extended radiator. These acoustic modes are than the radiusand smallerthan the wavelength,energy is scattered foundthrough an eigenfunction/eigenvectoranalysis or singularvalue back along the cylinderaxis and into the surroundingmedium. To decompositionanalysis of the radiationoperator. The eigenvalueor characterizethis phenomenon,the shell is consideredto be locally re- singularvalue associatedwith a given mode is directly proportionalto activefrom -- •o to 0, and rigid from 0 to •o along the x axis. A wave the radiationefficiency of that mode.Here, tbe frequencydependency of of knowntype is incidentfrom x= -- •o and excitesa reflectedwave and the acousticmodes of a baffledbeam is examined.Further, the depen- acousticwaves originating from the vicinityx=0. Pertinentasymptotic dencyof the radiationefficiencies and modeshapes on the numberof resultsare obtainedincluding the reflectioncoefficient of the reflected degreesof freedompermitted in the derivationof the radiationoperator waveand the far-fieldacoustic radiation pattern of the scalteredwave. is investigated.11 is demonstrated that the accuracy of the acoustic [Work supportedby ONR and by the William E. Leonhardendowment modal representationdepends on the numberof degreesof freedom to PennsylvaniaState University.] permittedin the derivationof the radiationoperator. The mostefficient acousticmodes are leastsensitive to increasingdegrees of freedom.The leastefficient acoustic modes are mostsensitive to changesin degreesof 9'.3O freedom.This behaviorhas significantimpact on applicationsof the 3aSA6. Accuratefinite elementmethods for fluid-loadedplates. Karl exterioracoustic modal approach that seekto exploitthe leastefficient Grush (Div. of Appl. Mech., Dept. of Mech. Eng., StanfordUniv., modes. Stanford,CA 94305-4040) and Peter M. Pinsky (Stanford Univ.,

Stanford, CA 94305-4020) 10:15 The designand analysisof new finite element methodsfor the 3aSA9. Focusing of sound power flow for sound incident on a steady-stateresponse of fluid-loadedReissner-Mindlin plates is pre- structure in water. Robert Hickling (Natl. Ctr. for Phys. Acoust., sented.In this study,new methodsare developedthat are moreaccurate Univ. of Mississippi,University, MS 38677) than standardfinite elementmethods in their ability to representwave propagationfor coupledproblems in structuralacoustics. Generalized Computationof sound-powerflow for soundwaves incident on a Galerkin least-squares(GGLS) finite elementmethods have been em- solidsphere in water showsvarious degrees of focusingalong the axis ployedpreviously to enhancethe accuracyof the finiteelement approx- and in the wake of the spheredepending on the materialproperties of imation for the uncoupledstructural problem [K. Grosh and P. M, the sphere.This contrastswith a rigid immovablesphere that has no Pinsky,in Proc.Second Int. Conf.Math. and Numer.dspects of Wave sound-powerflow insideand a shadowzone in the wake. Visualizations Propagatior•edited by R. Kleinmanet al. (June 1993)] and the uncou- are presentedthat showthe focusingeffect as a functionof frequencyfor pled acousticproblem [I. Harari and T. J. R. Hughes,Comput. Meth- a number of different materials. ods Appl. Mech. Eng. 87 (1991)]. Complexwave-number dispersion analysisis usedboth to designthe new methodsand characterizetheir 10:30 accuracy.Results comparing the finiteelement dispersion relations to the analyticdispersion relations for the fluid-loadedReissner-Mindlin 3aSAI0. A comicrison of strnetural intensity formulations. Yong platedemonstrate the enhancedaccuracy of thesenew GGLS methods Zhangand J. Adin Mann, lII (Dept. of Aerosp.Eng. and Eng. Mech., over the standardGalerkin finite elementimplementation. Iowa State Univ., Ames, IA 50011 )

Much pastresearch concerning structural intensity has focused on 9.'45 the structuralintensity formulation and measurementmethods. For the structuralintensity in a thin plate,different formulas were derived based 3aSA7. A spectraldescription for the effectsof multiple point masses on differentassumptions. Pavie's structural intensity formula [G. Parle, in fluid-loadedplates. Kenneth A, Canefare, Jerry H. Ginsberg,and J. Sound Vib. 49(2), 221-230 (1970)] was basedon classicalplate John Babish (The George W. Woodruff School of Mech. Eng., theory,which is describedby Lagrange'sequation of motion.A more GeorgiaInst. of Technol.,Atlanta, GA 30332-0405) generalderivation was perfumed by Romanoeta]. [Proceedingsof the The wave-number-basedformulation of the surfacevariational prin- International Congresson Intensity Techniques,CETIM, 137-142 cipledescribes the surfacepressure and displacement as a comparatively ( 1990)], which wasbased on three-dimensionalelasticity. In this paper, smallset of interactingwaves. It enablesone to poscquestions of para- a structuralintensity formula is derivedby simplifyingRomano's struc- metricsensitivity from a globalperspective. A two-dimensionalproblem tural intensityformula usingMindlin's assumptionfor thin plate theory of an elasticplate in an infinitebaffle with pinnedboundary conditions that considers the rotary inertia and shear effect. The differencesbe- is considered.A seriesof line massesattached to the plate, at regular tween the formulationswill be discussed.From plate velocitymeasure- and irregularspacings is considered.The specificmass distribution is mentsfor an aluminumplate at singlefrequencies, the structuralinten- replacedin theSVP formulation by an arbitrarycontinuous distribution sity is calculatedbased on the above-mentionedintensity formulas. In

1815 J. Acoust.Soc. Am., VoL 94, No. 3, Pt. 2, Sept. 1993 126th Meeting:Acoustical Society of America 1815 addition,the input mechanicalforce function is estimated.Results show putedstatistics that help assessthe impactof observationerror. How- that the input powerfrom structuralintensity and the input mechanical ever,discussions in the acousticsliterature typically fail to addressthis force match well with the experimentalresults. issue.The presentworkmodels feedforward active control as a regres- sion of complex-valuedvariables, and showshow to apply two basic regressiondiagnostics: the F-test and the t-test.Also discussedare the 10:45 physicalsignificant of the "costfunction" being minimized by the re- 3aSAII. The characteristicsof the radiated noise from open grid and grassion,and the assumptionsthat mustbe maderegarding the variance baseulebridges. J. M. Cuschieri (Ctr. for Acoust. and Vib., Dept. of of the measur•nenterror. The techniquesare demonstratedby numer- OceanEng., Florida Atlantic Univ., Boca Raton, FL 33431) ically simulatinga simplesystem in which radiationfrom an axisym- metriccylindrical shell is controlledby oscillatingforces applied on the When vehiclestravel acrossthe grid sectionof an open grid or shell surface.[Work supportedby David Taylor Model Basin and baseulebridge, noise is generatedwhich for most type of grid configu- ONR.] rationshas a very strongtonal characteristicin the frequencyrange between150 and 250 Hz. To investigatethe mechanismby which this 11:30 noiseis generated,and identifypossible noise mitigation procedureg a series of measurements of both sound and vibration levels have been 3aSAI4. Feedforward control with the higher-barmonic, performedon 12 basculebridges with differenttypes of grid. The grid time-averaged, gradient (H-TAG) descent algorithm. Dorene typescan generallyhe classifiedinto threeconfigurations, two of which Kewley, Robert L. Clark (Dept. of Mech. Eng. and Mater. Sei., Duke are of a rectangularor squareshape, while the third configurationhas Univ., Durham, NC 27708-0300), and Steve C. Southward (Lord diagonalmembers and is generallyreferred to as four-waygrid. For the Corp., Cary, NC 27511) rectangular-shapedgrids, both the vibration and the soundspectra ex- hibiteda dominantpeak at a frequencythat scaledwith the speedof the A noveladaptive filter structurehas been proposed for the controlof vehicleand a typical length of the grid spacing.For the four-way grid, systemscharacterized by higher harmonicresponse. The control ap- the spectrumdid not showa very strongpeak, but was more broadly proachhas beendesignated the higher-harmonictime-averaged, gradi- distributedin frequency.The generaloverall sound level was not much ent (H-TAG} descentalgorithm. In the H-TAG algorithm, a single differentfrom one bridgegrid type to another.The grid is an open frequencyreference input is all that is requiredto implementthe con- structureand its radiationefficiency in the 200-Hz regionis very low. troller. The remainingharmonics are generatedinternally based upon This makesthe tire a potentiallysignificant source of noise.[Work simpletrigonometric relationships. In addition,the algorithmis ideal sponsoredby FDOT.] for structurescharacterized by slowlytime-varying parameters since no systemidentification is requiredto implementthe algorithm.Results from simulationsand experimentsindicate that the proposedapproach 11.'00 offersa uniquemethod of achievingsignificant levels of attenuationin the harmonicvibration or acousticresponse of structures. 3aSAI2. Active control of sound power using acoustic bas's functions. Koorosh Naghshineh (Acoustics and Radar Technol. Lab., SRI International, 333 Ravenswood Ave., Menlo Park, CA 11'.45 94025) and Gary H. Koopmann (Penn StateUniv., UniversityPark, 3aSAI5. Active structural acoustic control with broadband PA 16802) disturbancesand real time structural wave-numborsensing. Julien P. An improvedmethod of active structuralacoustics control is pre- MailLardand ChrisR. Fuller (Vib. and Acoust.Labs., Dept. of Mech. sentedthat is basedon the minimizationof the total power radiated Eng., Virginia Polytech. Inst. and State Univ., Blacksburg, VA from any structureexpressed in termsof a truncatedseries sum. Each 24061-0238) term of this sum is relalzxl to the couplingbetween the orthogonal The presentwork givesfurther developmentsand experimentaltest- eigenveetorsof the radiation impedancematrix (referred to as "basis ing of a new time domainstructural sensing technique for predicting functions"} and the structural surfacevelocity vector. The basisfunc- wave-numberinformation and acousticradiation from vibrating struc- tions act as surfacevelocity filters. These acousticbasis funetious are tures. Most structure-borneactive soundcontrol approachesnow tend foundto be weakfunetious of frequencybut their correspondingweight- to eliminatethe useof microphoneslocated in the far fieldby developing ing coefficientsincrease monotonically with frequency.The minimiza- sensorsdirectly mountedon the structure.In order to reducethe con- tion of the radiated power is shownto result in a structuralsurface trol authority and complexityrequired to minimize soundradiation, velocityvector that couplespoorly to thoseacoustic basis functions that thesesensors should be designedto provideerror informationthat is accountfor high efficiencysound radiation. This strategyis demon- solelyrelated to the radiatingpart of the structuralvibrations, i.e., the stratednumerically for a clamped-clampedbaffled beam in air. An un- supersonicwave-number components. The approachdiscussed in this expectedbenefit of the controlstrategy described is that it providesa paperis basedon estimatingsupersonic wave-number components cou- rationalprocedure for selectingthe numberand placementof actuators pled to acousticradiation in prescribeddirections. The spatialwave- and sensorson a structurefor effectivecontrol. This developmentis numbertransform is performedin real time usinga setof pointstruc- significantsince this procedure doe not requirea prioriknowledge of the tural sensorswith an array of filtersand associatedsignal processing. dynamicsof the structure. Experimentalresults on planar radiatorsshow that only a few point sensorsare required to provide accurateradiation information over a 11:15 broad frequencyrange. The useof the sensingapproach is then exper- imentally demonstrated in the time domain LMS active control of $aSAI3. A regression-based approach for s•nulating feedforward broadbandsound radiated from a vibrating plate. [Work supportedby active noise control, with regression diagnostics for assessing the ONR.I impact of measurement noise. C. E. Ruekmart (Aenust. Technol.

Dept., David Taylor Model Basin, Bethesda,MD 20084-5000) and 12.'00 ChrisR. Fuller (VirginiaPolytech. Inst. andState Univ., Blacksburg, VA 24061) 3aSAI6. Design of feedforward ASAC systemsby eigenfunction assignment. Ricardo A. Burdisso and Chris R. Fuller (Vib. and Current numerical techniquesfor simulatingfeedforward a•tive Acoust. Labs., Dept. of Mech. Eng., Virginia Polytech.Inst. and State noisecontrol in the frequencydomain are mathematicallyequivalent to Univ., Blacksburg,VA 24061-0238) the techniquesrequired for linearleast-squares regression. Measurement error in the controlsystem error sensorsplays a role analogousto that The traditionaldesign approach of feedforwardcontrol sys•rus in- of observationerror in a statisticalregression. In thestatistics literature, volyes the selection of number and location of the actuators and sensors regressionsare alwaysaccompanied by regressiondiagnostics, i.e., corn- basedon somephysical understanding of the system.This empirical

1816 J. Acoust.Soc. Am.,VoL 94, No. 3, Pt. 2, Sept. 1993 126thMeeting: Acoustical Society of America 1816 methodologyyields satisfactory results for simplestructures and sinu- Sommerfeldt (Graduate Program in Acoust., Penn State Univ., soidalinputs. However, such an heuristicapproach can easilyresult in University Park, PA 16802) an inefficientcontrol system with unnecessarylarge numberof control channelsfor complexstructures and morerealistic disturbances. In this Adaptivecontrol of the bendingwave field in a finite beamis sim- wok an efficientformulation is presentedfor the optimumdesign of ulatedusing a classicalEuler-Bernoulli analytical model and a dual- actuatorsand sensorsfor structurally radiated sound reduction.The techniqueis basedon the modificationof the eigenstructuresuch that actuator filtered-x feedforwardcontroller. Three different inteosity- the systemresponds with the weakestset of modalradiators. The tech- basederror signal strategies are comparedfor multiplelocations on the niqueis applicableto both narrowbandand broadbandexcitations. The beamin andout of the nearfield of the actuators.The goalis to actively formulationis demonstratedfor controllingthe odd-odd modesof a minimizethe propagatingbending wave power where the five-element simplysuppoRed plate drivenby a point forcelocated at the centerof errorsensor array may be located in thenear field of theactuators. Since the plate.The radiationdue to the firstthree odd-odd modes is reduced the error array must be effectivein the near field, the idea of simulta- with a single-input, single-output(SISO) controller.The controlactu- neouslyminimizing all five accelerometersignals was rejected.Reults ator and error sensorare implementedwith piezoelectric(PZT) ceram- from usingan instantaneousintensity error estimatewere ineffective due icsand polyvinylidenefluoride (PVDF) films,respectively. It is shown to the nonlincarityin the adaptivecontrol error gradient.Results from that the optimum actuator and sensorconfiguration yields excellent minimizingthe intensity(rather than intensity-squared)were accept- globalsound reduction. [Work supportedby ONR.] ableand consistent with the experimentalresults of Sommerfeldt[Som- merfeldteta/., J. Acoust.Soe. Am. 93, 2370 (A) ( 1993}]. A newerror 12:15 methodbased on an intensitytransfer function plant also produced 3aSAI7. Adaptiveconffol of bendingwave intensityin a finite beam. acceptablesimulation results. [Work supported by the GEM Fellowship David C. Swanson,Cassandra Gentry, Sabih I. Hayek, and Scott D. Program.]

WEDNESDAY MORNING, 6 OCTOBER 1993 MAJESTIC BALLROOM, 9:00 TO 11:40 A.M.

Session 3aSP

SpeechCommunication: Tribute to Franklin S. Cooper

Katherine S. Harris, Chair Haskins Laboratories, 270 Crown Street, New Haven, Connecticut 06511

Chalr's Introduction---9:00

Invited Papers

9:05

3aSPI. Technologyfor people. Mark Haggard (MRC Inst. of Hear. Res.,University Park, Nottingham NG7 2RD, UK) Successfulapplication of scienceand technology to improvehuman welfare, as seen in the careerof FrankCooper, requires a sensitiveawareness of humanneeds and limitations. This talk illustrateshow the drivefor scientificunderstanding has interacted withconcern for humanwelfare in producingtwo typesof instrument(auditory warnings and auditory diagnostic or screening devices)in whichthe MedicalResearch Council of the UK hasmade major investments in recentyears. Successful development requiresa goodgrasp of engineeringprinciples, well-judged investment in enablingtechnologies, correct description of the need to be met, and evaluation of the real life usefulnessof the devices.

9:30

3aSP2. Reading,reading machines, and communicationsresearch. Alvin M. Liborman (Haskins Lab., 270 Crown St., New Haven, CT 06511 )

What knowledgeor habitof mindmust would-be readers command that mastery of speechwill nothave taught them? Surely, that is the firstquestion one must answer if one is to understandthe readingprocess and the ills that attendit. Yet the question could hardly be accommodated,let aloneanswered, within the theoryof speechthat wasalmost universally accepted when Frank Cooperentered the field.It thereforecounts as a majorachievement of his researchthat otherswere able to gain from it a critical insightinto the relationbetween the biologicallyprimary processesof speechand the biologicallysecondary processes of reading, and thus to seemore clearly the difficultiesthat besetthe progressionsfrom the one to the other.

9:55

3aSP3. Speechsynthesis by rule, text-to-speech,and aids for parsonswith disabilities. Hector Raul Jaykin (SpeechTechnol. Lab., Panasonic Technol., Inc., 3õgõ State St., Santa Barbara, CA 03

Speechsynthesis by ruleand its subsequentdevelopment into text-to-speech have progressed into both science and technology for useby the generalpopulation, particularly by persooswith disabilities.This paperbriefly reviews the advancesin speech synthesisby rule and text-to-speechand thenfocuses on a newdevelopment--the use of text-to-speechin a speechtraining system for deaf children.The methoduses the acousticparameters that a text-to-speechsystem supplies to its formantsynthesizer and

1817 J. Acoust. Soc. Am., VoL 94, No. 3, Pt. 2, Sept. 1993 126th Meeting: AcousticalSociety of America 1817 convertsthem to pseudoarticulatoryparameters equivalent to parametersmeasured from instrumentsmonitoring the child's production.For example,the relativefrequencies of the nasalpole and nasal zero are convertedto a "nasalizationindex" equivalentto the outputof a nasalsensor. The methodenables a studentto typeany utteranceshe/he wants to learnand see a representationof the articulationof that utterancethat correspondsto the feedbackreceived from instruments.Preliminary testingof the useof the methodwill be reported.

10:20

3aSP4. Design of auditory prosthesesto aid speechenmmunication. Sigfrid D. Soli and Robert V. Shannon (House Ear Inst., 2100 W. 3rd St., Los Angeles,CA 91024)

Researchon the treatment of heating impairment and deafnesshas, in recent years, increasinglyfocused on auditory prosthesesthat canaid speechcommunication in bothquiet and noise.For theseprostheses to be mosteffective, several research goalsmust be achieved.First, the residualcapacity of the impairedauditory system must be determined.Next, the essential acousticinformation for speechrecognition must be characterizedand re•oded to exploitthe residualauditory capacity. Finally, algorithmsand circuits that can extract and process this information are required.Efforts toward these goals in hearingaids and in cocMearand brainstemimplants will be described.The binauraldirectional hearing capacity of individualswith sensorineural hearingimpairment has defined the main focusof this hearingaid researchbecause of its potentialto improvespeech commu- nicationin noise.In this implantresearch, the channelcapacity and channelinteractions of the electricallystimulated auditory systemhave receivedmajor attentionbecause of the effectsof theseinteractions on speechcoding for multi-electrodeimplants. Methodsfor characterizingthe residualcapacity of an individual,techniques for usingresidual capacity to aid speechcommu- nication,and resultsfrom perceptualtests obtained with real-time,laboratory-based processors will be discussed.

10:4.5

3aSPS. Imaging techniquesfor the larynx and vocal tract. Hajime Hirose (Faculty of Medicine, Kitasato Univ., 1-15-1 Kitasato, Sagamihara,228 Japan)

A recentlydeveloped method of digitallyimaging vocal fold vibrationwas applied for the analysisof the natureof diplopho- nia, whichis definedas the simultaneousproduction by the voiceof two separatetones. In the presentsystem, a speciallydesigned tele-endoscopeis attached to a single-lensreflex camera that housesa solid-statesensor at the positionof the film plate.when the shutteris released,an imagescan is madeunder computer control, and imagesignals are storedin the imagememory. The image can be reproducedand displayedfor later analysis.In the caseof diplophonia,it wasrevealed that there is an asymmetryin the vibratoryfrequency of the left and right vocalfolds associated with quasiperiodicvariation in the speechwaveform. As for the imagingtechnique for the vocal tract, a preliminaryresult of observationof the inner structureof the tongueusing tagging snapshotMRI will be presented.

ContributedPapers

11:10 11:25

3aSP6. Tracking the gliding tongue and lips: Articulatory under•hont 3aSP7. The stability of a temporal distinction:Vowel length in Thai. or perceptualovershoot or ..2 Leigh Lisker (Haskins Labs., 270 Arthur S. Abramson (Haskins Labs., 270 Crown St., New Haven, CT Crown St., New Haven, CT 06511-6695 and Univ. of Pennsylvania, 06511-6695 and Univ. of Connecticut, Storrs, CT 06269-1145) Philadelphia,PA 19104) This is part of a larger effort to test the robustnessover speaking stylesof acousticproperties that underliephonologieal contrasts. So At the last ASA meetingit was shownthat for a set of synthetic muchof the knowledgecomes from the studyof citationforms that one vowel-glide-vowelsequences varying in F2 trajectoriesa rangeof fre- might wonderwhether in runningspeech the presenceof much top- quenciescan equally well serveas mid segmentsin patternsidentified as down information and other contextual cues does not lead to the im- English/iwi/and/uyu/. Many of thesemid segments,when lengthed poverishmentof someof the bottom-upphonetic information. A good and presentedin isolation,resemble the highfront roundedvowd LY],so candidatefor possibleinstability is relativeduration as a meansof dis- that when shortand intervocalicone might expectthem to be heardas tinguishingphoneroes. The Thai language,in both productionand per- the glide [q], at leastby phoneticallytrained listeners. However, per- ception,uses relative duration to distinguishits "short" and "long" ceptualdata suggestthat intended[q] in/i/--/i/is heardas/w/, while vowels. In this study vowel durations were measuredunder three con- in/u/--/u/it is/y/. Assumingthe syllabificatious/iSwi/and/uSyu/, ditions. (1) Eight minimal pairs of words were recorded in carrier onemight then expect an initial [q] to beheard as/w/in [qi] andas/y/ sentencesby four native speakersat two rates, normal and fast. {2) in [qu]. Test data indicateotherwise. Unlike/iwi/and/uyu/,/wi/and Casualunrehearsed conversations were recordedby two couples.{3) /yu/ show no overlap of F2 values in their initial steady-state Many wordsand short expressionstaken from eachperson's part of a segraents•tbere is instead a range of F2 values for which listeners conversationwere read aloud by that person. The data show that the report both not-/wi/and not-/yu/. Thus for English/w,y/the steady- quantitydistinction in Thai is ratherstable. The overlapin the pooled stateand transitional intervals have different perceptual initially data from running speechlargely disappearsonce certain contextual and mediaBy. [Work supportedby NIH Grant No. HD-01994 to factorsare taken into account.[Work supportedby NIH Grant HD- HaskinsLaboratories.] 01994 to HaskinsLabs.]

1818 J. Acoust.Soc. Am.,VoL 94, No. 3, Pt. 2, Sept. 1993 126thMeeting: Acoustical Society of America 1818 WEDNESDAY MORNING, 6 OCTOBER 1993 COLUMBINE ROOM, 8:00 A.M. TO 12:00 NOON

Session 3aUW

Underwater Acoustics: Shallow Water Noise I

Kenneth E. Gilbert, Chair AppliedResearch Laboratory, Pennsyloania State University.P.O. Box 30, State College,Pennsylvania 16804

Chair's Introduction-•8:00

Invited Papers

8:05

3aUWI. Shallow-waternoise•A review. RobertJ. Urick ( 11701Berwick Rd., SilverSpring, MD 20904) Like mostaspects of underwatersound, the noise in thesea received its first quantitative attention during World War II, when a team under the venerable acoustician V. O. Knudsen made measurements in the shallow coastal waters off Southern California and Florida--ostensiblyfor the purposesof acousticmines and harborprotection . At that time too, the pernicious snappingshrimp of thewarm shallow tropic waters of thePacific were investigated. One of theprincipal features of shallowwater noiseis its variability--fromplace to placeand time to time. Yet it may be saidthat thereare only three major noisesources in shallowwater: ships and other man-made activities at moderatelyclose ranges, biologics, and the windor waves.Strangely, when the first two of theseare absent,the noiselevels in shallowwater at frequenciesabove I kHz or so are the sameas in deepwater; the so-called"Knudsen" curves have long been used in deepwater. At lowerfrequencies, many shallow locations are oftenmore quietthan deepwater because of the absenceof deep-goingfavorable transmission paths. When environmental conditions can be estimated,one's knowledge of shallow-waternoise should be goodenough to permit a predictionof the expectablenoise level at an arbitrary location--at leastas goodas one'sprediction capability of transmissionloss out to usefulranges. [Work supported by the AppliedResearch Laboratory, The PennsylvaniaState University, and the Officeof Naval Researeh.]

8:30

3aUW2. Man-madenoise in shallowwater. StephenK. Mitchell (Appl. Res. Labs.,University of Texas,Austin, TX 78713) In manyimportant shallow water areas, merchant shipping, fishing, or seismicexploration activities are a prominentfeature. In suchregions, the ambientnoise levels in the frequencyrange from approximately10 Hz to 1 kHz are generallydominated by soundsrelated to theseactivities. Ambient noiselevels arc generallymuch higher than thosetypical of deep oceanregions; omnidirectionaland beamlevels show considerable temporal variability as noisesources move and changetheir activities.Noise data from measurementsin shallowwater regions will be summarized.In addition,the interactionbetween source characteristics, shippingdensities and trafficpatterns, propagation characteristics, and ambientnoise statistics will be discussed.[This work is supportedby the Officeof Naval Research,Code 234, underblock RL3B.]

8:55

3al.Fr/3. Biologicalsources of noisein coastalwaters. Peter L. Tyack and TerraneeHowaid (Woods Hole Oceanogr.Inst., Woods Hole, MA 02543)

Underwaterbiological sounds are transientevents. Durations range from microsecondsto tensof seconds,frequencies from < 10 Hz to > 100 kHz, and sourcepressure levels up to > 220 dB re: I pPa at Im. While eachsound is producedby one individual,many sounds occur in chorusesthat may involvethousands of simultaneoussources. Some crustaceans produce loud impulsivenoise in the 2-20 kHz range.These animals are commonenough in manyshallow areas to dominatethe ambientnear 10 kHz. Eveningfish choruses seasonally dominate the ambientin many shallowwaters in the 100-1000Hz frequencyrange. While whalesand dolphinsare lessnumerous than the animalslisted above, many species produce sounds of sufficientintensity to affectthe ambient.For example,during their winter breedingseason fin whalesproduce series of 20-Hz pulseslasting I s at sourcelevels of 180 dB re: I pPa at Im. Dolphin echolocationclicks may reachsource pressure levels > 220 dB with spectral peaks50-150 kHz. Dolphinsare alsoskilled mimics of manmadesounds, which may lead to unpredictedinterference.

9:20

$aUW4. Acousticradiation from breakingwaves. Li Ding and David M. Farmer (Inst. of OceanSci., P.O. Box 6000, Sidney, BC VgL 4B2, Canada}

Observationsof the sound from breaking surface waves using a smallhydrophone array illustrate the temporal and spatial characteristicsof this soundsource and its dependenceon the surfacewave field. Such observations provide a sourcedescription that mighthave application in ambientnoise model development. By trackingthe propagationspeed of the breakingevent its wavescale is inferred;other measured properties include breaking length, duration, and spatial separation. Analysis indicates that the dependenceof breakingprobability on the fourth momentof the wavespectrum is consistentwith a linear model.The measuredspeeds of breakingevents imply that their scaleis lessthan the dominantwind-wave scale. Group structureof wave

1819 J. Acoust. Soc. Am., Vol. 94, No. 3, Pt. 2, Sept. 1993 126th Meeting: AcousticalSociety of America 1819 breaking,in whichthere is a tendencyfor wavesto breakrepetitively at twicethe waveperiod and spacedone wavelength apart, alsooccurs but is more readily identifiableat lower wind speeds.

9:45-10:00 Break

ContributedPapers

!0:00 10:45

3aUW5. The source pressure field arising from wave-wave 3aUW8. Model calculation for deviation of ambient noise statistics interactions in shallow-water environments. A. C. Kibblewhite and from signal statisticsin shallowwater. JacobGeorge (Naval Res. C. Y. Wu (Dept. of Phys.,Univ. of Auckland,Private Bag, Auckland, Lab., Code7176, StennisSpace Center, MS 39529} New Zealand} It hasbeen reported that cumulativedistribution functions (CDFs) Theoretical treatment of the noise source induced by wave-wave of a signalin shallowwater obeynormal distributions,while thoseof interactionshave beentraditionally based upon the assumptionof an ambientnoise deviate from this, in both casesindependent of depth[$. infinitelydeep ocean. Growing interestin the applicationof the wave- George,J. Acoust.Soc. Am. 92, 2304A ( 1992)].One cause of intensity inducedpressure field as an acousticsource in the determinationof the fluctuationsis internal waves,studied by path integral and moment sub-bottomgeoacoustic structure in shallow-waterareas calls for a methodsin deepwater [B. J. Useinskiet al., J. Aeonst.Soc. Am. 74, studyof the influenceof waterdepth on the physicalprocesses involved. 1474 (1983)]. In shallow water, internal waves have been shown to This paperpresents some results based on suchan extension.It shows behaveas solutions[J. Zhou and X. Zhaug, J. Acoust.Soc. Am. 90, how the depth-dependentsurface-wave dispersion relation and porosity 2042 (1991}]. For the time spansconsidered in the CDFs mentioned in the upper layerseffect the spectralproperties of the resultingULF above(25-320 s) intensityfluctuations caused by surfacewaves cannot noisefield in shallow-waterenvironments. [Work supportedby ONR.] be ignored.Results of a model calculationdesigned to contrastthe effectsof a stablesignal source below the surfacewith the effectsof ambientnoise sources moving with the surfacewill be presented.DVork 10:15 supportedby ONR.] 3aUW6. Measurements of the azimutlml distributions of very low-frequency noise with high resolution in a shallow water site in 11:00 the Mediterranean. Bruce K. Newhall (Appl. Phys. Lab., Johns HopkinsUniv., JohnsHopkins Rd., Laurel, MD 20723-6099) 3aUW9. A modified complex starting field for shipping traffic noise modeling. ChristopherJ. Burkhalter (Naval Res. Lab., Code 7181, An extremelylong horizontal towed array was used to perform StennisSpace Center, MS 39529-5004} high-resolutionnoise measurements at very low frequencies.The direc- tional measurementsin one shallowsite are comparedwith more ex- In current ambientnoise modeling efforts, commercial shipping is tensivemeasurements in deepwater. The verylow-frequency noise at all considereda major contributorto overall noiselevels and is modeled sitesis highly anisotropicdue to the high azimuthalresolution of the accordingly.The propagationof shippingnoise from the manysources discretemerchant shipping sources that dominateunderwater noise at to the receiveris effectedby useof any of a numberof high-fidelity thesefrequencies. The deepwater measurements were performed at sites acousticmodels. Almost all of thesemodels require an initialcondition in three oceans,covering an extremerange of shippingdensity condi- in the form of a verticalpressure field that is steppedout numericallyin tions, however,the shapesof the azimuthal distributionsof the noise range.This startingfield usuallytakes one of severalforms: a simpleor levelsare relativelyinsensitive to shippingdensity. The shallowwater modifiedGaussian distribution around a sourcedepth, a normalmode noise exhibits azimuthal spreadingnot apparent in the deep water. starter, a simple image (acoustic dipole} starter, or a Pade- From the loudestsources this spreadingmay partly obscurethe spa- approximatedparabolic equation starting field. The implicationsof a tially quiet regionsthat are otherwisepresent in directionsbetween loud nearsurface source are discussed,as well as effectsof low- versushigh- ships.Although they have differentshape parameters, both the shallow anglepropagation models and the effectsof complexreflection from the and deepwater data fall betweenWeibull and gammadistributions, and necessarilyturbulent surface.Additionally, the use of the Gaussiandis- are well fit by generalizedgamma distributions. The effectsof multipath tributionas a sufficientstarting approximate is analyzedfor long-range, fadingare diminishedby the spatialaveraging across the long aperture. deep-waterresults. [Work supportedby ONR and NRL.] Low-resolutionnoise distributions, obtained from subaperturesof the array, are dominatedmore by multipathfading, and approachgamma 11:15 distributions. 3aUW10. Description of a noise model for shallow water: RANDI-11I. J. ErnestBreeding, Jr. (Naval Res. Lab., StennisSpace Center, MS 39529-5004}, Marshall Bradley, Melanie Hebert, and 3aUW7. Modeling of echoesfrom extended targets in shallow water. Wait McBride (Planning Systems,Slidell, LA 70458) T. Baas,M. Rosario,W. Chang,and R. Deavenport (Naval Undersea Warfare Ctr., New London, CT 06320) Version III of the researchambient noise directionality (RANDI- III) noisemodel is describedand illustrated.The objectiveof the model Echoesare generatedand comparedfor extendedtargets in a shal- is to make predictionsof the ambientnoise at low to mid frequencies low water environmentusing the total target-mediumbroadband fre- (10 to severalhundred Hz) for highly variableenvironmental condi- quencyresponse function and the frequencyrepresentation of the trans- tions typical of shallowwater and coastalareas. The receivercan be mired signal.The two-way medium responseis calculatedusing a eithera horizontalor verticalline array. Shippingand local wind are hybrid SAFARI/generic sonar model (GSM) environmentalmodel. assumedto be the dominantsources of noise.Ships are treatedas dis- The target frequencyresponse is found nsinga model of distributed crete sourcesof noise.The ship noiseis propagatedto the elementsof targetsand elasticspheres. The combinationof the targetand medium the receiverusing a wide-anglefinite elementparabolic equation. The frequencyresponses gives the full frequencyresponse, or form function, contributionsfrom all shipsare addedcoherently. The environmental for the target, mediumsystem. The productof the total form function and shippinginformation are automaticallyextracted from severalda- with the frequencyspectrum of the incident signal is computedand on tabases.[Research supported by The Officeof Naval Research,Program inverse1•1•-[ is performedto predictthe receivedsignal, or echo,from Element 62435N with technicalmanagement provided by the Naval the object.[Work supportedby ONR Code 231.] ResearchLaboratory, Stennis Space Center, MS.]

1820 J. Acoust.Soc. Am.,VoL 94, No. 3, Pt. 2, Sept. 1993 126th Meeting:Acoustical Society of America 1820 11:80 managementprovided by the Naval ResearchLaboratory, Stennis SpaceCenter, MS.] 3aUWII. Ambient noise predictionsfrom deep to shallow water. J.

Ernest Breeding,Jr. (Naval Res. Lab., StcnnisSpace Center, MS 11:45 39529-5004), Marshall Bradley, and Melanie Hebert (Planning Systems,Inc., Slidell,LA 70458) 3aUW12. A ray-model theory on spatial correlation and vertical directivity of surface-generatedambient noise in shallow water. The RANDI-III noisemodel is used to make predictionsof the RenheZhang, Yi He, BaixianZhu, and DinghuaGuan (State Key omni noiselevel, horizontal noisefield, and the vertical noisefield for Lab. of Acoust., Chinese Acad. of Sci., Beijing 100080, People's realworld examples of broadand narrow transects from deep to shallow Republicof China) water.For comparison,some noise predictions are alsomade with the The ambientnoise in shallowwater is morecomplicated than that in ANDES-II noise model. This is of interest since these two noise models the deep sea, and it has greatergeographical and seasonalvariations are fundamentallydifferent in severalways, including the methodsused sincethere is a strongbottom interaction.A theoreticalmodel of am- to propagatenoise and the approachesused to treat ship sources.It is bient seanoise including surface-noise sources and a stratifiedmedium foundthat at the deeperwater portions of the transects,the RANDI-III ocean is discussed.The noise sourcesare assumedto be statistically and ANDES-II predictionsof the omni noiselevels and the horizontal independentdirectional point sourcesdistributed over the seasurface. noise fields can be similar. However, the RANDI-III and ANDES-II The effectsof the surface-sourcefeature, velocity profile, and bottom predictionsof the verticalnoise field at thesesame water depthsare propertyon ambientnoise are studied.In general,the ray theoryis quitedifferent. At theshallow water sites the predictions of noiseare not suitablefor calculatingthe contributionof near-fieldsources, whereas possiblewith ANDES-II. Examplesillustrating the differencesand sim- the normal-modetheory is appropriatefor far-fieldsources. In this ilaritiesof the RANDI-III and ANDES-II predictions,as well as the paper,a ray-modetheory suitable for near-and far-fieldsources is de- RANDI-III predictedvariations in the noisealong the transectsfrom veloped.The conciseformulas for calculatingthe intensities,spatial deepto shallowwater will be presented.[Research supported by The correlation,and vertical directivity of ambientnoise are presentand Office of Naval Research,Program Element 62435N with technical somenumerical simulations are given.

WEDNESDAY MORNING, 6 OCTOBER 1993 BILTMORE ROOM, 9:00 A.M.

Meeting of AccreditedStandards Committee S2 on Mechanical Vibration and Shock

to be held jointly with the

U.S. TechnicalAdvisory Group (TAG) Meeting for ISOfrC 108 MechanicalVibration and Shock

S. I. Hayek, Chairman S2 AppliedResearch Laboratory, Penn State University,P.O. Box 30, StateCollege, Pennsylvania 16801

D. F. Muster,Chairman, U.S. TechnicalAdvisory Group (TAG) for ISO/TC 108, MechanicalVibration and Shock 4615 O'Meara Drive, Houston, Texas 77035

StandardsCommittee S2 on MechanicalVibration and Shock.Working group chairs will presentreports of their recentprogress on writingand processing various shock and vibration standards. There will be a reporton the interfaceof S2 activitieswith those of ISO/TC 108 (the TechnicalAdvisory Group for ISO/TC 108consists of membersof S2,S3, and other persons not necessarily membersof thosecommittees) including a report on the currentactivities of ISO/TC 108, and plansfor the next meeting.

SCOPE OF S2: Standards,specifications, methods of measurementand test, and terminology in the fieldsof mechanicalvibration and shock,and condition monitoring and diagnostics of machines,but excludingthose aspects which pertain to biologicalsafety, tolerance, and comfort.

1821 J. Acoust.Soc. Am., Vol. 94, No. 3, Pt. 2, Sept. 1993 126th Meeting:Acoustical Society of America 1821 WEDNESDAY Al•ERNOON, 6 OCTOBER 1993 TERRACE ROOM, 12:55 TO 2:15 P.M.

Session3pAB

Animal Binacoustics:Acoustical Monitoring of Animal Populations

$ohn R. Potter, Chair ScrippsInstitution of Oceanography,9500 GilmanDrive, La Jolla, California92093-0238

Chalr's Introduction--12:55

ContributedPapers

1:00 Lab., ScrippsInst. of Oceanogr.,San Diego, CA 92152-6400)

3pAB1. Tracking zooplankton at sea with a three-dimensional Over the past severalyears, the Marine PhysicalLaboratory has acoustical imaging system. Duncan McGehee and Jules S. Jaffe designed,built, and deployedinnovative, large-aperture sensor systems (Marine Phys.Lab., ScrippsInst. of Oceanogr.,Univ. of California,San in order to measurethe low-frequencyproperties of the oceanacoustic Diego, La Jolla, CA 92093-0205) field. In many of theseexperiments, baleen whale vocalizationshave been a significantfeature of the infrasonicsound field. For example, The AcousticalImaging Group in the Marine PhysicalLaboratory, finbackwhale (Balaenopteraphysalus) sounds have been recorded by a ScrippsInstitution of Oceanography,has developed a real time, high- 120-element,900-m, vertical line array of hydrophones.Finback whale resolutionthree-dimensional acoustical imaging system for use in the soundswere also recordedby a 12-element,165-m, vertical array of ocean.The system,called Fish TV (FTV) is designedfor the observa- "TRIFAR" elements(i.e., each element recordssimultaneously the tion of macrozooplanktonand small fish. FTV cansynoptically examine threecomponents of acousticparticle velocity and pressure).In addi- a 16ø by 16ø volume of seawaterwith a l-Hz frame rate. The sonarhas tion, blue whale (Balaenopteramusculus) signals were the overwhelm- recentlybeen used at seain two configurations.In the firstexperiment, ing featureof a data set recordedby someneutrally buoyant, freely the sonarwas mounted40 m deep,looking laterally from the research drifting, acousticparticle motion/acousticpressure sensors. Finally, platformR/P FLIP. A videocamera provided ground-truthing. In the new-designocean bottom seismometers (OBS) have recordedboth fin- secondexperiment, the sonarwas attached to a PhantomDS4 remotely back and blue whale signals.Where possible,these measurements are operatedvehicle and deployed,again with videoground-truthing. Re- usedto estimateboth the positionand the actual time signatureof the suitsindicate that the systemcan be usedboth to track animalsin three sourceby removingthe effectsof multipatharrivals. dimensionsand to estimatetheir density.

1:45 1:15 3pAB4. Detection of salt-marsh mosquitoswarms in remote mangrove 3pAB2. Application and comparisohof neural nets for marine swamps.Richard W. Mankin (Agric. Res. Service,Insect Attractants, mammal call classification. lohn R. Potter (MPL 0238, Scripps Inst. Behavior, and Basic Biology Lab., P.O. Box 14565, Crainesvillc,FL of Oceanogr.,Univ. of California,San Diego, 9500 Gilman Dr., La 32604) Jolla, CA 92093-0238) and David Mellinger (Cornell Laboratory of Ornithology, Ithaca, NY 14882) Swarmsof.4edes taeniorhynchus mosquitos produce sounds that can be detectedfrom 10-50 m at 25-35 dB (re: 20 pPa) in a quiet environ- Recentwork has successfullyapplied a linear matchedfilter to calls ment. The loudness of the swarms is above the 21-dB acoustical back- madeby Bowheadwhales recorded off the coastof Alaskain frequency- groundbetween frequencies of 0.6 and 3.4 kHz in an isolatedsalt marsh, time (spectrogramspace) to detectand classifymarine mammalcalls. but below the 40-60 dB backgroundof a typical urban environment. This methodrelies on an empiricalmatrix weightingfor the matched- Individual.4e. taeniorhynchushave wingbeat frequencies (+standard filter coefficients.A neuralnet, trainedon spectrogramestimates as the error} of 4414-21 Hz and 7034- 17 at 24øC, detectablefrom 3 cm at featurevector space, offers two advantagesover this approach;(a) the 22-25 dB in an anechoicchamber. In the marsh, femalesbeat their equivalentweighting matrix is determinedby trainingand may coverage wingsat 400-500 Hz and malesat > 800 Hz, dependingon their size to a more optimal solution and (b) the responseof a neural net is and the temperature.Because of their low wingbeatsound intensities, nonlinear and can embody more sophisticatedresponses. A simple the only individual•4e. taeniorhynchusmosquitoes that can be detected three-layerfeedforward neural net is ideally suitedto this application are thoseflying within 2-5 cm of the microphone.These frequency and and has been implementedon 204 calls, of which 163 were usedfor loudnessmeasurements suggest that it is technologicallyfeasible to con- trainingand 31 kept as "unseen"test data. The neutralnet wasconfig- struet an acousticaldevice for remotesurveillance ofAe. taeniorhynchus ured to identify both whale calls and other mammal interference.The swarms or individuals attracted to a bait. Further studies to correlate successrate includingfailures in both estimateson training data was detectionof wingbeatsounds with numbersof mosquitoescaptured at a 88%. The combined false-positiveand false-negativewhale detection bait are in progress. errors on unseendata was only 7%, which comparesvery favorably with any other known method.The neural net approachis compared with the matchedfilter and the role of the hidden neuronsand equiva- lent weightingmatrix are discussed.[Work supportedby the Officeof 3pABS. Acoustic features of tonal "grunt" calls in baboons. Michael Naval Research.] J. Owren, ChristopherD. Linker, and Matthew P. Rowe (Dept. of Psychol., Univ. of Colorado, Campus Box 173, P.O. Box 173364, 1:30 Denver, CO 80217-3364)

3pAB3. Fortuitous underwater acoustic measurements of baleen The acousticfeatures of "grunt" calls recordedfrom free-ranging whale vocalizationaby large aperture arrays. G. L. D'Spain, J. A. baboons(Papin ursinus)in Botswanawere investigated.Analysis pa- Hildebrand, M. A. McDonald, and W. $. Hodgkiss (Marine Phys. rameterstypical of thoseused to analyzehuman speech were employed

1822 J. Acoust.Soc. Am., Vol. 94, No. 3, Pt. 2, Sept. 1993 126thMeeting: Acoustical Society of America 1822 and thesesounds were found to closelyresemble speech vowels in sev- typicallyfound between 0 and 5 kHz, in a pattern resemblingthat of the eral respects.They were brief (approximately97 ms) andhighly tonal vowel "schwa." Variation due to individual caller and behavioral con- with a stablefundamental frequency (approximately 122 Hz.) Like text are discussed,as well as the implicationsof thesefindings for rela- adult human males,baboons are estimatedto have a vocal tract length tionshipsbetween nonhuman primate vocalcommunication and human of 17 cm (g}ottis to lips) and this concordancewas reflectedin the formant structureof the grunts. Three formants (range 2 to 7) were speech.

WEDNESDAY AFTERNOON, 6 OCTOBER 1993 SILVER ROOM, 1:00 TO 3:20 P.M.

Session3pPA

Physical Acoustics:Observing Scattering with Time-FrequencyRepresentations

Charles F. Gaumond, Chair AcousticsDivision, Physical Acoustics Branch, Naval ResearchLaboratory, Washington, DC 20375-5000

Chair's Introduction--l:00

Invited Papers

1:05

3pPAI. Time-frequencydescription of signals•A review. Leon Cohen (Dept. of Phys.,Hunter Collegeand GraduateCenter of CUNY, New York, NY 10021)

The frequencycontent of manynatural and man-madesignals changes drastically with time andstandard Fourier analysis doesnot fully describesuch highly nonstationary signals. Among such signals are speech,sonar and radar,optical images, and biologicaland geophysicalsignals, In the past 10 yearsthere have been dramatic strides made in our abilityto understandand processsuch signals. The basicidea is to developa methodthat describes the intensity of a signaljointly in timeand frequency. This wouldgive the frequency content at eachinstant of timeand hence describe how the spectrum is changingin time.A review is presentedof the ideasand methodsthat havebeen developed to describea time-varyingspectrum and theirapplication is illustratedwith concreteexamples from a widevariety of fields.

1:35

3pPA2. Decompositionof scatteredwaves from an isolatedelastic object with time-frequencyrepresentation. Nai-chyuan Yen (Phys. Acoust. Branch, Naval Res. Lab., Washington,DC 20375-5320) In observingthe scatteringphenomena from an isolatedelastic object, one wouldlike to understandthe compositionof the scatteredwaves so the characteristicstructure of the scatterercan be estimated.This paperreviews such an inversescattering problemin termsof wavepacket decomposition. Particularly, the focusis on a heuristicapproach that hasbeen developed from the studyof acousticscattering. The basicscheme of thisapproach is to examinethe coherenceproperty of the wavesignature of the scatteredwaves and to computeits energydistribution in a joint timeand frequency representation. Also shown is howto applysignal synthesis techniques to determinethe dominantcomponents, namely wave packets, expressed as the naturalframe (basis),the buildingblock for the formulationof the scatteredwave. The magnitudeand the phaseof eachwave packet arc evaluatedby algorithmsthat treatthem as theindependent nonorthogonal components from a setof linearequations. Examples of the responseof the scatteredwaves from shelltype elasticobjects arc usedto illustratethe physicalimplication of this decompositionmethod in resolvingtbe inverse scattering problem. It is concludedthat thewave packet decomposition by means of the naturalframe (basis) can be considered as a generalizedGabor and/or wavelettransform. Their relationshipsare discussed throughthe fundamentalsof linear functionalanalysis.

ContributedPapers

2:05 differenttime and ka resolution;(ii) measurementsof the leaky Lamb- wave decayrates from the smoothedWDF for differentka regions 3pPA3. Time-frequencyspectrograms of impulsescattering by shells: showinggood agreement with ray theorybased on complexpartial-wave Quantitative comparisons with ray theory for Lamb wave indexpoles; and (iii) evaluationof a derivedquantity, the localtempo- contributions.D.H. Hughes (815 Main St., Boonville,MO 65233) ral varianceof the WDF as a functionof frequency,showing how the and P. L. Marston (Washington State Univ., Pullman, WA temporalspread changes near a resonance[D. H. Hughesand P. L. 99164-2814) Marston, J. Acoust.Soc. Am. 94, 499-505 ( 1993)]. The temporalvari- The Wignet distribution function (WDF) and quantitiesderived ance at resonancewas in generalagreement with the ray theory predic- from it wereused to investigatehigh-frequency scattering processes for tions for the dominant scattering contribution. Structure in the a sphericalshell in water [D. H. Hughes,Ph.D. thesis,Wash. State smoothedWDF was also investigatedfor the prompt backward wave Univ. (1992)]. The investigationincludes: (i) displayof Gaussian contributionthat causesa prominentscattering enhancement at high smoothedWDF for ka as large as 500 with smoothingfunctions of frequencies.[Work supportedby ONR.]

1823 J. Acoust.Soc. Am., Vol. 94, No. 3, Pt. 2, Sept. 1993 126th Meeting:Acoustical Society of America 1823 2:20 wave behaviorto Rayleighwave behavioras the shell becomesa solid cylinder;,(g) cancellationof the monopoleand dipolemodes for fre- 3pPA4. The predictionof echoesfrom underwaterstructures in the quenciesless than ka=3 occurringat thicknessh/a=O.05; (h) the time-frequencydomain. G. Gannaurd (Naval SurfaceWarfare Ctr., polesof the normalmode series solution coinciding with the highlights White Oak Detachment,RI4, Silver Spring, MD 20903-5640) and seenin the frequencydomain. H. Strifors (Natl. DefenseRes. Establishment,Sundbyberg, Sweden)

An earlier study [J. Aenust.Soc. Am. 93, 2412 (A) (1993)] of 2:50 echoesfrom submergedelastic shdls in the combinedtime-frequency (t-f) domainis continued.Wigher and pseudo-Wignerdistributions as 3pPA6. Time-frequency representationof scattering from a target in well as time-windowedFourier transformsare used[cf. L. Cohen,Proc. a boundedmedium. Angie Sarkissian,Charles F. Gaumond (Naval IEEE 77, 941 (1989)]. Thesedistributions extract from the echoesthe Res. Lab., Washington,DC 20375-$350), and Timothy J. Yoder time evolutionof the target resonancesthat may be presentin the fre- (SFA, Inc., Landover, MD 20785) quencyband of operation.Selecting suitable carrier frequencies for the incidentpulses and appropriatespectral windows, it is possibleto pro- Time-frequencyrepresentations applied to target scatteringenable duce (t-f) displayslinking resonance features to specifictarget charac- one to observetarget characteristicsthat arc of particular interest in teristics.It becomesclear that this type of display is helpful in the inversescattering problems. In this work suchrepresentations are ex- processingof the echoes,and in the identificationof the scatterer's tendedto targetsplaced in a shallowwater environmentwhere target materialproperties and geometricalshape. Broader/narrower time win- characteristicsas well as shallowwater characteristicsappear in the dowscontrol the amountof detail in the resulting(t-f) plots,which can time-frequencydomain. The Gabor transformationis applied to scat- be adjustedat will. This is illustratedwith examplesexhibiting results in tering from an elasticshell placed in a boundedmedium to displaythe a colorizedthree-dimensional format as beautifulas practicaland in- combinationof the waveguideeffects (shallow water propagation)and formative. These examplesinclude the useof various realistic incident the targeteffects (elastic wave propagation).The useof suchrepresen- pulses,targets, and viewingwindows that highlightthe target-ID capa- tations for classificationpurposes is discussed. bility of the approach. 3.•5 2:35 3pPA7. Adaptive wavelet analysis of transient signals in structural 3pPA5. Time, frequency, and thickness analysis of mannstatic acoustics.P. R. Stepanishen(Dept. of OceanEng., Univ. of Rhode scatteringfrom an infinite steel cylindrical shell immersedin water. Island, Kingston,RI 02881), Q. Huynh, and T. Greene (Naval Timothy J. Yoder (SFA, Inc., 1401 McCormick Dr., Landover, MD UnderseaWarfare Ctr., Newport,RI 02841) 20785), Louis R. Dragonctte, and Charles Gaumond (Naval Res. Linear and quadratictime-frequency transforms are usedto inves- Lab., Washington,DC 20375) tigate and characterizetransient signals from severalwave propagation The monnstaticscattering for an infinite cylindrical steel shell is problemsin structuralacoustics. The transformsinclude: the short-time analyzedfor frequenciesup to ka= 10.0. The shellthickness is varied spectrum,Wignet type representations,and waveletmethods. Advan- from h/a=O.001 to h/a=0.999. The time, frequency,and thickness tages and disadvantagesof the various representationswithin the dependenceof the scatteringis graphicallyanalyzed to determinethe presentcontext are presented.Particular emphasisis placedon using physicalprocess(es) responsible for the scattering.This analysisreveals the wavelet packet method of Coifman to analyze and characterize the followingprocesses: (a) The Lamb wavecircumnavigating the cyl- complextransient signals from variousstructural-acoustic transmission inder; (b) a 180-degphase shift in the specularscattering as the shell pathswith dispersivecharacteristics. Adaptive proceduresare usedto becomesthick; (c) the coincidencefrequency of the flexuralwaves with determineoptimal time-frequencylocalization by usingthe best basis the radiation medium; (d) a drastic decreasein the "•' of the modes functionsfor the classof dispersivesignals of interest.Various features supportingthe flexural wavescaused when the circumnavigatingflex- and parameterextraction methods based on the local maxima of the ural wavesbegin to radiate efficiently;(el the onset of the creeping wavelettransform at eachscale are presentedfor severalcomplex tran- waves as the shell becomes thick; (f) the transition of flexural/Lamb sientdispersive signals. [Work supportedby ONR.]

WEDNESDAY AFTERNOON, 6 OCTOBER 1993 COLUMBINE ROOM, 1:25 TO 3:30 P.M.

Session3pUW

Underwater Acoustics: Shallow Water Noise II

Kenneth E. Gilbert, Chair AppliedResearch Laboratory, Pennsyluania State University,P.O. Box 3• State College,Pennsylvania 16804

Chair's Introductio•l:25

Invited Papers

1:30

3pUWl. Ambient noise in shallow seas: Propagationissnes. Ira Dyer (Dept. of Ocean Eng., MIT, 77 MassachusettsAve., Cambridge,MA 02139)

Whateverthe sourceof ambientnoise in a shallowsea, propagation to a distantreceiver shapes in a major way its spectral character,its temporalproperties, and its coherenceor spatialdistribution functions. Any one ambientnoise mechanism is generallyan incoherentsuperposition of a largenumber of similarelemental sources. Thus propagation modeling for ambient

1824 J. Acoust.Soc. Am., VoL 94, No. 3, Pt. 2, Sept.1993 126thMeeting: Acoustical Society of America 1824 noisemust address the multiple source question, and as well the modeling can take advantage of simplificationsoften afforded by multiplepath averaging. In thiscontext, the main confounding elements of shallowsea propagation including, but notlimited to, downwardrefraction, sloping bottoms, sediment interaction, rough bottom scattering, and watercolumn fluctuations are re- viewed.In suchcomplicated propagation channels the noiseis modifiedin importantdetail, although much of its character remainsbroadly recognizable. 1:55

3pUW2.Spatial structure of ambientnoi•e in shallowwater. Michael J. Buckingham(Marine Phys. Lab., Scdpps Inst. of Oceanog.,La Jolla, CA 92093-0213) Apartfrom the nature of thesources, ambient noise in shallowwater is distinguishedfrom that in deepwater through the proximityof thebottom. As withacoustic propagation, the bottom introduces a modal structure into the noise, evident through noiseeigenrays with discrete grazing angles that are characteristic of the modes. There is alsoa continuousnoise component, associatedwith overheadsources. Since it is largelycontrolled by the bottom,the modalstructure is characterizedby the geoacousticproperties, including the stratification,of the sediment.As the modalstructure determines the directionality,or equivalentlythe spatial coherence in thevertical, it shouldbe possible, through measurements with vertically aligned hydro- phones,to establishthe bottom properties through measurements of the noise field in thewater column. For example, the sound speedof a fluid sedimentclose to the water-seafloorinterface can be estimatedfrom observationsof the verticalnoise coherence overthe frequency range 500 Hz to I kHz (M. J.Buckingham and S. A. S.Jones, $. Acoust.Soc. Am. 81, 938-946 ( 1987)].This inversiontechnique can be extendedto the caseof a shearsupporting bottom and, at sufficientlylow frequency,may yield informationon thesub-bottom structure. [Research supported by ONR.]

2:20-2:30 Break

2:30-3:30

PANEL DISCUSSION: PanelMembers.' I. Dyer, M. J. Buckingham

WEDNESDAY AFTERNOON, 6 OCTOBER 1993 BOETTCHER CONCERT HALL, DENVER CENTER FOR THE PERFORMING ARTS, 3:30 P.M. TO 4:30 P.M.

Performance/Lecture

Voicesof Peopleand Machines

Ingo Titze, Presenter Recordingand ResearchCtr., DenverCenter for thePerforming Arts, 1245 Champa Street, Denver, Colorado 80204 and WendellJohnson Speechand Hearing Ctr., Universityof Iowa, Iowa City, Iowa 52242

WEDNESDAY AFTERNOON, 6 OCTOBER 1993 BOETTCHER CONCERT HALL, DENVER CENTER FOR THE PERFORMING ARTS, 4:30 P.M.

Plenary Session:Business Meeting and Awards Ceremony

Richard H. Lyon, Chair President,Acoustical Society of America

BusinessMeeting

Presentation of Awards

Pioneers of Underwater Acoustics Medal to Homer P. Bucker

Silver Medal in AcousticalOceanography to ClarenceS. Clay

Silver Medal in PhysicalAcoustics and EngineeringAcoustics to StevenL. Garrett

1825 J. Acoust.Soc. Am., Vol. 94, No. 3, Pt. 2, Sept. 1993 126th Meeting:Acoustical Society of America 1825 THURSDAY MORNING, 7 OCTOBER 1993 GRAND BALLROOM A, 8:30 TO 11:25 A.M.

Session 4aAA

Architectural Acousticsand EngineeringAcoustics: Teleconferencing Facilities

David L. Adams, Cochair David L. Adams Associates,Inc., 1701 Boulder Street, Denver, Colorado 80211

James E. West, Cochair AcousticsResearch Department, AT&T Bell Laboratories,Murray Hill, New Jersey07974

Chair's Introduction---8:30

Invited Papers

8:35

4aAAI. Acousticecho cancellation for stereophonicteleconferencing. M. Mohan Sondhi,Dennis R. Morgan, and JosephL. Hall (Acoust. Res. Dept., AT&T Bell Labs., Murray Hill, NJ 07974-0636)

In long-distancetelephony, echoes arise due to impedancemismatches at variouspoints in the telephonecircuit. Adaptive line echo cancelorshave been usedsuccessfully for over a decadeto combatthis problem.Echoes also arise in teleconferencing,due to acousticcoupling between microphone and loudspeakerin eachconference room. This problemis similarto the line echo problem;however, the echopaths are muchlonger and muchmore variable in this case.In this papera further complicationthat arisesif stereophonictransmission is usedfor teleconferencingis discussed:There is an inherentnonuniqueness in estimatingthe echopaths. It appearsthat the only way to resolvethis nonuniquenessis by somehowdecorrelating the signalsin the two stereo channels.Several methods of decorrelationare discussedand how they affectadaptive echo caneoilerperformance as well as stereophonicperception is shown.

9:00

4aAA2. New systemsfor intereommunications•Synergy of acousticsand telecommunications. •ark ^. Holden (JaffeHolden ScarbroughAcoust., Inc., 114A WashingtonSt., Norwalk, CT 06854) Properroom acoustics for audioteleconferencing and videoteleconferencing facilities has been, at best,a matterof guesswork. In this paper, room acoustictreatments are varied in material and locationwithin a typical conferenceroom and the results studiedusing binaural analysis techniques. The relationshipbetween room acoustics,speech intelligibility, speech interference, and mechanicalnoise levels in regardto teleconferencingsystems will be exploredin a quantitativemanner, including the effects of "echocancelling" technology.

9:25

4aAA3. A new approachfor measurementtelephone systems and teleconferencingapplications. H. W. Gierlich (HEAD Acoust. GmbH, Kaiserstr. 100, 5120 Herzogenrath3, Germany)

New telephoneand teleconferencesystems show increasingly nonlinear time variant behavior.Measurement results of such systemsare highlycorrelated to the measurementprocedure used especially for conformancetests and measurements according to severalstandards. It is highly desirableto achievecomparable measurement results in differentlabs. Theseresults should correlatewell to the subjectiveimpression the user has when telephoningwith the measureddevice. To achievethe desired performance,a suitabletest signal must have voice signal properties. On the otherhand, measurements have to be carriedout in a very shortperiod of time in order to guaranteequasistationary behavior during the time of measurement.To achievethis, a "compositesource signal" was developed. The signalconsists of a voicedsound on 50 ms at the initial phase.This voicedsound is followedby a measurementsignal, a pseudorandomnoise sequence. To get a modulationtypical for speech,the signalis followedby 100-mspause. Variations of the signalare describedfor differentmeasurement applications. Measurement results derived from differentsystems, including various signal processing techniques, are presented.

9:50

4aAA4. Architectural acousticsdesign parameters for teleconferencingfacilities. Dennis A. Paoletti (Paoletti Associates,Inc., 40 Gold St., San Francisco, CA 94133)

Audio and videoteleconferencing equipment and room facilitieshave emerged as one of the fastestgrowing areas of com- municationand businesstechnology. The acousticenvironment is an extremelyimportant component in (determining)the successof theteleconferencing experience. Additionally, other environmental factors such as: architectural space planning, design aesthetics,color, thermal, lighting, operations, etc. must also be considered. This paper will presenta summaryof thesignificant acousticalparameters and key environmentalfactors that impactthe designand functionaluse of audioand videoteleconfer- encingfacilities, whether teleconferencing equipment is portableor permanentlybuilt-in. (This paper acknowledges the work of

1828 J. Acoust.Soc. Am.,Vol. 94, No. 3, Pt. 2, Sept. 1993 126th Meeting:Acoustical Society of America 1826 MichaelSullivan, Kurt Graffy,and JohnWhitcomb, audiovisual consultants and teleconferencingsystems designers at Paoletti Associates,Inc. )

10:15

4aAAS.Audio for videoteleconferencing. David A. Berkley (Acoust.Res. Dept., AT&T Bell Labs.,600 MountainAve., Murray Hill, NJ 07974-0636)

Videoteleconferencing, especially that supported by inexpensivelow-bit rate connections, isan exploding area. It isclear that thereare severetrade-offs to be madeas bit-rateis lowered.However, although everyone agrees that audiois a vital part of audio/videoteleconferencing, little is understoodabout what trade-offs are involved in optimizingthe audio and the relationship betweenthe audioand videoon a specifictype of conferencelink. The relationshipbetween audio and videotransmission delay, cameratracking errors and lag, audio bandwidth and other related issues are discussed. Implementation of experiments,based on the HuMaNet [D. A. Berkleyand J. L. Flanagan,AT&T Tech.J. 69, 87-97 (1990)] platform,is alsodescribed.

ContributedPapers

10:40 thedevice simultaneously. The firstsignal was a bias,which temporarily causedthe telephoneto operatein a well-definedmanner. Bias signals 4aAA6. Acousticaspects related to the performanceof teleconference usedin this work includednoise, noise bursts, and speechfragments. facilities. Bradley P. Basnett (TeleconferencingDept. 4Y44, The secondsignal was used for the actualmeasurement. It wasapplied Bell-Northern ResearchLtd., P.O. Box 3511 Station "C," Ottawa, ON at a low level relative to the bias, so the effect of the bias was not KIY 4H7, Canada) disturbed.The measurementsignal used was a seriesof very fast sine Room acousticdesign and electroacousticsystem integration are sweeps,processed using an enhancedtime delay spectrometryalgo- paramountto the performance,and thereforeeffectiveness, of telecon- rithm. This method was chosen to enable simulated free-field measure- ferencingfacilities. Some key elements that needto be consideredduring mentof the telephonein an ordinaryroom. The measurementsetup will the designand implementationstages are (a) the effectsof roomacous- be described,and measurementresults will be shownand explained. ticson transmitted,received, and in-roomspeech communications; (b) Benefits and limitations of the method will be discussed. the effectof transmissionbandwidth on intelligibilityand audioquality 11:10 in the teleconferencesuite; (c) the naturalhesSof interaction over a telephonenetwork; (d) the impactof acousticand electroacousticde- 4aAAS. A new artificial ear for telephonemeasurements. Winfried vicesin a visual communicationsmedium; (e) room ambient noiseand Krebber,Stefan B/Jhmc [Inst. for Commun.Eng., AachenUniv. of potentialnoise sources. These elements are examinedin light of the Technol. (RWTH), MelatenerStr. 23, D-52056 Aachen,Germany], recentdesign, implementation, and operationof 12 teleconference(au- and Hans W. Gierlich (HEAD AcousticsGmbH, Herzogenrath, dio and video) suites.Details of designchoices and acousticmeasure 4 Germany) mentsof theseteleconference suites will be presented. Opiniontests show the importanceof the acousticalleakage between the handsetand the humanear for the subjectivespeech transmission 10:55 quality of telephonesets. Artificial ears, which are now used for tele- 4aAA7. A binary method for measuring the electroacoustic phonemeasurements, do not allow measurementswith variableleakage. characteristics of hands-free telephones. John R. Bareham Usingan artificialear formedas an individualhuman ear doesnot lead (Consultant in Electroacoust.,20 Rogers Ave., Marlborough, MA to reproducibleresults. Both problemsare avoided by this new ear. It 01752) has a simplifiedshape, which is determinedby only a few geometrical parameters.Thus the transmissioncharacteristics can be describedby a Hands-freetelephones often are designedwith performancefeatures mathematicalmodel. Nevertheless it approximatesa humanear, refer4 that makeit difficultto obtainmeaningful electroacoustic measurements ring to the dependenceof the leakageand the transmissioncharacter- usingsimple methods. Compressors, limiters, threshold detectors, noise isticson the force appliedto the handset.Measurements using the at4 guards,and other more complexspeech-sensitive functions change the tificial car arc reproducible and show high conformity with telephone'selectroacoustic characteristics depending on the type and measurementsof handsetsat humanears. Implemented in an artificial levelof signalapplied to it. To realisticallyaccount for suchvariables, head,the ear can alsobe usedto measurehands-free telephones. The electroacousticcharacteristics of several hands-freetelephones were directional characteristics of the artificial ear in a free sound field show measuredusing a binarymethod, in which two signalswere appliedto all main structures of monaural outer ear transfer functions.

1827 J. Acoust. Soc. Am., Vol. 94, No. 3, Pt. 2, Sept. 1993 126th Meeting: Acoustical Society of America 1827 THURSDAY MORNING, 7 OCTOBER 1993 GRAND BALLROOM D/E, 8:25 TO 11:45 A.M.

Session 4aAB

Animal ,Acoustical Oceanography,and Underwater Acoustics: Effects of Noise on Marine Mammals I

W. John Richardson, Chair LGL Limited, 22 FisherStreet, P.O. Box 280, King City, OntarioLOG 1KO, Canada

Chair's Introduction---8:25

Invited Papers

8:30

4aAB1. Behavioraland hearingresponses of pianipedsto rocket launchnoise and sonicboom. Brent S. Stewart (Hubbs-Sea World Res. Inst., 1700South Shores Rd., San Diego, CA 92109) Loud launchnoise and sonicbooms from somemilitary space vehicle launches from VandenbergAir ForceBase impact pinnipedson the mainlandand at SanMiguel Island, California, and may cause stampedes, temporary threshold shift or, less likely,permanent hearing damage. Maximum fast A-weighted (MFXA) soundlevels approximately 4.8 milesdownrange during the launchof threeTitan IV rocketswere 93.2, 92.7, and 93.0 dB; averagesound exposure levels were between 98.9 and 101dB. Harbor sealsfled into the water in responsebut manyreturned to land within severalhours. A sonicboom was recorded at San MiguelIsland during one launch. Its peakfiat sound-pressurelevel was 129.5 dB andmaximum fast A-weighted sound level was 86.2dB; virtually all of theenergy was below 500 Hz. Pinnipedbehavioral responses were mild andbrief. Predicted overpressures for focusedsonic booms from the Titan IV rocketare substantially greater ( >•150 dB). Noninvasivehearing tests using ABR and OAE techniquesare beingused to determineif pinnipedssuffer temporary threshold shifts or permanenthearing damage from exposureto thosesonic booms.

8:45

4aAB2. Walrus responseto offshoredrilling operations. Jay Brueggeman (EbascoEnvironmental, 10900 N.E. 8th St., Bellevue, WA 98004)

Walrus responseto drilling operationsin the ChukchiSea was evaluated between 25 Juneand 19 October,1989. Aerial and vesselobservations of walruses were conducted at threeprospects in conjunctionwith acousticmeasurements of the operations. Walrusresponse was evaluated before, during, and after they passedthe drillsiterelative to varioussound sources. Over 350 groupscomprising approximately 4500 walruseswere observed in the prospects.Walrus response was greatest during ice management,when the icebreakercrisscrossed the prospect.Animals moved deeper into the packice, where the noiselevel from theicebreaker was an estimated15-25 dB aboveambient (97 dB). Onceice management stopped or becamemore focused at the drillsite,walruses began to reoccupyformerly used areas. Under these circumstances, walruses displayed some behavioral responsesthat rapidly decreased beyond 0.46 km (0.25nmi) from the icebreaker. Walruses showed little response toother drilling operations.These results show that walruses reacted to icebreakeractivities, but responses varied according to theintensity of ice management.This variability offers opportunities to incorporate precautions to minimizedisturbance to walrusesduring future drilling operations.

9:00

4aAB3. Experimentswith an acousticharassment system to limit seal movements.Bruce Mate (Hatfield Marine Sci. Ctr., Oregon State Univ., Newport, OR 97365) To controlthe distributionof sealsaround salmon hatcheries, pond tests were conducted using swept frequencies between 2 and20 kHz. Thisdid not affect salmonid movements or reproduction.Aperiodic 12- or 17-kHzpulses of varyingduration were effectiveat levelsof 187dB re: I pPain reducingseal abundance near several hatcheries and pen aquaculture facilities. A few larger(possibly older) seals habituated or wereless sensitive, and foraged with modified techniques. For sealions, the same systemproduced a dramaticinitial startle response but was otherwise totally ineffective. Many marine mammals react to moving soundsources even if loudstationary sources are tolerated. Early in thisexperimentation, swept frequencies were eliminated for simplicity.However, the illusion of motionas simulated by Doppler-likesweeps may have been lost in theprocess. Operant conditioningresearch suggests that an aversivestimulus is bestmaintained when used aperiodically. If severalstimuli have a deterrenteffect, this effect can be sustained longer by intermixing the stimuli to avoidor delayhabituation. These principles may also be applicableto intentionalharassment and industrialeffects.

9:15

4aAB4.Long-range respenses of belugasand narwhals to ice-breakingships in the NorthwestPassage. Kerwin J. Finley•) (LGL Ltd., EnvironmentalRes. Associates,P.O. Box 280, King City, ON LOG lK0, Canada) and CharlesR. Greene (GreeneridgeSci., Inc., SantaBarbara, CA 93110)

1828 J. Acoust.Soc. Am., Vol. 94, No.3, Pt.2, Sept.1993 126thMeeting: Acoustical Society of America 1828 Responsesof belugasand narwhalsto ice-breakingships were studiedduring three springseasons. The two speciesreacted differently.Belugas exhibited as shipsapproached at distancesof 35-50 kin; receivednoise levels ranged from 94-105 dB re: 1 •tPa (20- to 1000-Hzband). Sound spectrographs revealed a toneat 105Hz froman ore-carriership at 130km. Presumed alarmcalls indicated that belugaswere aware of the ore carrierat 85 km (101 dB, 20- to 1000-Hzband level); they moved up to 80 km awayfrom ice-breaking operations. In contrast,narwhals showed subtle "freeze" responses and dispersed slowly. Ship approachescaused narwhals to ceasevocalizing temporarily whereas belugas emitted noisy alarm calls. Narwhals returned to disturbanceareas faster than belugas and resumed normal activities when received noise levels from ice-breaking operations were as highas 120dB. Theseresponses occurred at unprecedentedranges, but no previousfield studies had beenconducted in areas with marinemammal populations unaccustomed to industrialnoises. The disparitybetween field observations and theory,based on belugaaudiograms, is examined.Results of Finleyet al. [Can.Bull. Fish. Aqua. Sci. 224 ( 1990)]are augmented by additional acousticalanalyses. [Work supported by CanadianDept. of IndianAffairs & NorthernDevelopment.] a)Present address: 10232 SummersetPlace, SidneyV8L 4X2, Canada.

9:30

4aABS.A modelfor assessingthe impactof vesselnoise on odontocetecommunication. Susan E. Coscns (CanadaDept. of Fisheriesand Oceans,501 UniversityCres., Winnipeg, MN R3T 2N6, Canada)

Offshoreindustrial noise sources ensonify marine mammal habitat and may maskdetection of socialsignals and important environmentalsounds. A probabilisticmodel of sounddetection was developed for assessingthe impact of underwatericebreaker noiseon signaldetection by belugawhales and narwhals.The probabilityof detectingsample signals, in the absenceof vessel noise,was compared to thatof detectingthe same signals in shipnoise, using the MV ARCTIC,as a samplenoise source. Analysis of signaldetection probabilities showed that loud signals centered on the5-kHz critical band were more severely masked by ship noisethan were quiet 5-kHz signals or loud2-kHz signals. Thus long-range calls seem to bemore susceptible to masking by ship noisethan are short-rangecalls. The modelcould also be appliedto othercritical bands of interest.Changes in the probability of detectingvessel noise, as estimated by the model,were also correlated with changesin belugaand narwhal behavior, observed in responseto the vesselin operation.

9:45

4aAB6, Hearing abilities of killer whales(Orcinus orca), David E. Bain (Marine World Foundation,2001 Marine World Pkwy.,Vallejo, CA 94589), Birgit Kriete (Univ. of BritishColumbia, Vancouver, BC V6T 2A2, Canada),and Marilyn E. Dahlheim (Natl. Marine Mammal Lab., Seattle, WA 98115)

A studyof hearingabilities of killer whaleswas conducted to helpassess the impactof noiseproduced by vessels.The study had five objectives:(1) determinethe rangeof frequenciesthat killer whalescan hear; (2) determinethe abilityto hear these frequenciesin thepresence of bandlimitedmasking noise; (3) determinewhether vessel noise affects the ability to hearpure tones; (4) determinewhether noise from differentdirections has differentmasking properties; and (5) determinethe ability to detect simulatedkiller whalesounds in the presenceof vesselnoise. Data werecollected using conditioned responses of fourcaptive killer whales.Conclusions reached include: killer whalesare sensitiveto a wide rangeof frequencies(0.5-105 kHz); noisereduces the abilityto detectsignals of similarfrequencies; very loud,low frequency,noise reduces the abilityto detectsignals even at much higherfrequencies; noise has the strongesteffect when it comesfrom in front of the whale,and the leasteffect when it is from the sideor behind;and the abilityto detectbroadband signals such as killer whalecalls and clicks is not substantiallyaffected by low levels of vessel noise.

10:00-10:15 Break

10:15

4aAB?.The effectsof noiseon dolphinecholocation. Whirlow W. L. Au and Paul E. Nachtigall (Hawaii Inst. of Marine Biol. and Naval Command, Control and Ocean Surveillance Ctr., RDT&E Div., P.O. Box 1106, Kailua, HI 96734)

The echolocationcapabilities of dolphinscan be seriouslyaffected by naturalambient and man-madenoise. Many echoloca- tion experimentshave been conducted at our facility to studythe effectsof noiseon the echolocationbehavior and capabilitiesof dolphins.When a belugawas transported from SanDiego Bay, Californiato KaneoheBay, Hawaii, the whaleadjusted its sonar emissionsto compensatefor the louderambient noise environment in KaneoheBay. It emittedhigher intensity signals which had peak frequenciesthat were approximatelyone octavehigher than in San Diego. Experimentswith echo-locatingdolphins have shownthat their target detectionand discriminationcapabilities can be severelydegraded by the introductionof maskingnoise. In mostsituations, the dolphinscompensated for the presenceof maskingnoise by emittingmore clicks per scanand by increasing their signal intensity. The responselatency defined as the time betweenthe cessationof the last click in a click train and the touchingof a responsepaddle also increased as the maskingnoise level increased. However, the effectsof noiseemanating from a specificlocation can be minimizedby a dolphinutilizing the directionalproperty of its auditorysystem.

10:30

4aABg. Interaural time discriminationin the bottlenosedolphin. P. W. B. Moore and DeborahA. Pawloski (The Naval Command, Control and Ocean SurveillanceCtr., RDT&E Div., San Diego, CA 9215•2-6267and SAIC, Kailua, HI 96734)

Binauralhearing is the advantageof two earsover one. Localizationstudies with marinemammals have shown that acoustic localizationunderwater is mediatedby the same binaural mechanismsused by other mammalsin air. Dolphin echolocation abilitiesare enhanced by the useof two separatereceivers. Au and Moore[J. Acoust.Soc. Am. 75, 255-262 ( 1984)]modeled the animal'shearing system as a two-elementarray usingreceiving beam pattern measurements. The presentstudy sought to measure

1829 d. Acoust. Sec. Am., Vol. 94, No. 3, Pt. 2, Sept. 1993 126th Meeting: AcousticalSociety of America 1829 the interauralphenomena of interauraltime differencediscrimination (ITD) and interauralintensity difference discrimination (IID). A dolphinwas trained to acceptcontact hydrophones, attached by suctioncups, to theouter surface of thelower jaw in the areaof the pan-boneand to performdetection threshold experiments. Audiometric data at severalfrequencies indicate that the dolphinminimum threshold for puretones may be 20 dB differentwhen measured with jaw phones.The first behavioral measures of ITD and lid discrimination and for a cetacean have been obtained. ITD and lid for clicks trains of various frequencies,presented with interclickintervals simulating various eeholocation target rangeswere collected.This methodof collectingaudiometric data representsa new approachfor assessingbearing capabilities in cetaceans.

10:45

4aAB9. High-frequencyhearing loss in old (25+ yearsold) male dolphins. S. H. Ridgwayand D. A. Carder (Biosci.Div., NavalCommand, Control and Ocean Surveillance Ctr., RDT&E Div., Code5107B, 49620 Beluga Rd., Rm. 200,San Diego, CA 92152)

Eightbottlenose dolphins (four male,four female)were studied in an acousticresponse time task[Ridgway et al., J. Acoust. Soc.Am. 89, 1967-1968(A) ( 1991)]. The animalswere trained to stationI m belowthe water surface and respond to a stimulus tone (St) deliveredthrough a hydrophonelocated I m in front of the blowhole.St duration varied from 60 to 450 ms and frequencieswere 20, 40, 50, 60, 70, 80, 100,and 120kHz. St were120 dB (re: 1/zPapeak to peakat I m) +24 dB in 6-dBsteps. With the dolphinat l-m depthand 1 m from the St hydrophone,the trainer starteda randomlyvariable 3- to 20-$t block.The computerselected St from a file in randomsequence and interval (1.1 to 2.1 s in 0. l-s steps)and offered St via a St generator. Animal responses(ARs are the whistleor pulsetrain) werereceived by anotherhydrophone, digitized, and stored. Each AR file with 20 to 200 St wasedited on a CRT displayof a 700 msSt window.No-AR trials,noisy trials, and wrongARs wereidentified. Threemales (ages 25, 29, and35 ) exhibitedhearing disability at the fourhigher frequencies. One female (age 33 ) showedsome lossabove 80 kHz, but two females(age 32 and 36) respondedto all frequenciesas did a male (age9) anda female(age 13).

11:00

4aABI0. Bioacousticsof baleanwhales: Prom infrasonics to complexsongs. Christopher W. Clark (Bioacoust.Res. Program, Cornell Lab. of Ornithol., 159 SapsuckerWoods Rd., Ithaca, NY 14850) and William T. Ellison (Marine Acoustics,Inc.)

One reasonfor concernover potential effectsof man-made soundson marine mammals stemsfrom the fact that most baleen whalesproduce intense, low-frequency sounds. Complete descriptions of vocalrepertoires are still lackingfor many of the 11 species,and our understandingof howwhales use sounds is poor.The applicationof passivearray techniques has provided unique and excitinginsights into the biologicalsignificance of whalesounds. Acoustic studies on bowheadwhales migrating off Point Barrow,Alaska and recent work on pelagicspecies (including blue, finback, and minke whales) clearly demonstrate that whales are vocallyactive and produce a varietyof signals.Whales counter-call, adopt distinctive call typeswhen traveling in acoustic herds,sing complex songs using two simultaneous,nonharmonically related voices, and produceextremely long, patterned sequencesof infrasoniccalls. These results support the conclusionthat soundsserve a varietyof importantcommunicative functions.There is alsoreason to believethat somewhales actively use surface reverberation as a navigationalcue. Thus the concernover the potentialimpact of man-madenoise on the whales'acoustic behaviors is legitimateand thisissue requires continuedattention. [Work supported by ARPA, ONR, andthe Department of WildlifeManagement, Barrow, AK.]

11:15

4aABII. Reactionsof bottlenoisedolphins, Tursiopstruncatus, and migrating gray whales, Eschrichtiusrobustus, to experimentalplayback of low-frequencyman-made noise. PcterL. Tyack (WoodsHole Occanogr.Inst., Woods Hole, MA 02543)

Playbackexperiments of low-frequencynoise to two speciesof cetaeeanwere linked to measurementsof transmissionloss in orderto relateresponses to received sound level. Coastal observation sites were selected to allowvisual tracking of animalsusing theodolites.The Tursiopsplaybacks involved a populationresident near Sarasota, FL, usinga 800-900Hz M-codestimulus with a sourcelevel of 170 dB re: I /xPaat 1 m. The identificationof individualdolphins of knownsex and agewith predictable movementpatterns permitted repeat playbacks to monitorhabituation. The Eschrichtiusplaybacks were performed as the whales migratedpast Big Sur, CA; eachwhale was only exposed once during its migration.A singleairgun (source level=226 dB) and severalcontinuous (source levels 151-163 dB) stimuliassociated with offshoreoil industrywere used. Observation of > 3500 migratingwhales showed significant responses. Whales slowed down and altered course at rangesof 1-3 km, somenear 0 dB SNR.Half of thewhales avoided exposure to continuousstimuli at levels> 117-123dB, to airgunpulses at levels> 170dB. Bottlenoseddolphins exposed to continuousM-code at levelsnear 120 dB showedno suchavoidance response.

11:30

4cAB12.Responses of graywhales, Eschrichtius robustus, to noise. MarilynE. Dahlheim (Natl. MarineMammal Lab., NMFS?AFSC, 7600 SandPoint Way N.E., Seattle,WA 98115) Responsesof gray whales to increasedlevels of noisewere documented during playback experiments. Nine sound parameters werecompared between control and experimental conditions: call rates, call types, frequency range (Hz), emphasizedfrequencies (Hz), receivedlevels of sound(dB re: I/zPa), callduration (s), callsexhibiting frequency modulation, pulses per series, and signalrepetition rates. Whale surface behavior (i.e., dive durations, movements, and abundance) was also investigated. Analyses yielded:a description ofcall types; a characterization of acoustical habitats; and a determinationof relationships between whale callsand habitats; and a determinationof relationships between whale calls and habitats. Gray whales employed multiple behavioralstrategies (e.g., modification ofcalling to optimize signal transmission andreception, movement out of the study area, etc.) to circumventincreased levels of noisein theirenvironment. Responses varied with sound source and may also differ with geographicalrange and/or generalbehavior.

1830 J. Acoust.Soc. Am., Vol. 94, No.3, Pt.2, Sept.1993 126thMeeting: Acoustical Society of America 1830 THURSDAY MORNING, 7 OCTOBER 1993 SPRUCE ROOM, 9:00 TO 11:30 A.M.

Session 4aEA

Engineering Acoustics: Underwater Transducers and Arrays

James M. Powers, Chair Naval UnderseaWarfare Center, Code2131, New London, Connecticut06320

ContributedPapers

9:00 contactwith the water and subsequentlylarger sheetswere used.A planar transientwavefront was achievedby applyinga step voltage 4aEAI. Standard reversibletransducer (USRD type E37} for high acrossthe sheet.Prior to the arrivalof wavesfrom the edgeof the sheet, frequenciesto 2.0 MHz at hydrostaticpressures to 20.7 kPa (3000 the radiatedwave was nearly unipolar and impulsivefor frequenciesup psi}. JamesA. Tiresand Larry E. Ivey (Naval Res.Lab., Underwater to I MHz. The transduceris usefulfor measuringthe backscatteringor Sound Reference Detachment, P.O. Box 568337, Orlando, FL reflectedimpulse response of objectsin water becausethe backscattered 32856-8337) or reflectedwave is nearly completelytransmitted through the sheet. A new pressure-stablereversible standard transducer, USRD E37, Thus a small broadbandreceiver can be placedbehind the sheettrans- has been developedat the Naval ResearchLaboratory, Underwater ducer.The transmissionwas demonstratedby measuringthe impulse SoundReference Detachment for the frequencyrange 100 kHz to 2.0 reflectedby a plate and the transducerwas usedto measurethe short- MHz at hydrostaticpressure to 20.7 MPa (3000 psi) with operating term impulseresponse by an elasticshell. After a sufficientlylong time, temperaturesfrom 5 to 35 øC within this frequencyrange. This USRD the receivedimpulse response is contaminatedby edge contributions. E37 maintainsa smoothresponse over the broad frequencyspectrum [Work supportedby ONR.] previouslycovered by both the USRD E27 and E8 standardtransduc- ers, which were not stable with temperatureand static pressure.The 9:45 E37 has been calibrated to 6894 kPa (1000 psi) at 3øC. Its unique sensorconfiguration design uses a lead titanatedisc sensor supported by 4aEA4. Application of multilayered structure for flow noise a butyl rubber ring. The facesof the sensorare coveredwith PRC reduction. SungH. Ko (Naval UnderseaWarfare Ctr. Detachment, PR-1538 polyurethaneand are held in placein the frame assemblyby New London, CT 06320) thin wire. The receiverpreamplifier assembly is speciallydesigned for high-frequencyoperation, with a built-inbypass relay to allowsignals to Turbulentboundary layer pressurefluctuations can be reducedby be transmitted.The cylindricallydesigned outer housingis madeof filteringof its wave-numberresponse with eithera finitehydrophone or polycarbonateand has beenstatically pressure tested to 31.026 MPa a hydrophonearray, or by filteringthe wave-numberresponse through (4500 psi). a layer(layers) of elastomer.The elastomerlayer is frequentlycalled an outer alecouplerand the multilayeredstructure is a generalizedouter decoupler.In generalpractice, hydrophone arrays are embeddedwithin 9:15 the outer alecouplerto reducethe turbulentboundary layer pressure fluctuationsand then mounted to an elasticstructure. The analysisof a 4aEA2. Variational principle modeling of ela• IV flextensional multilayeredstructure is presentedhere to evaluatethe transferfunc- transducers. Harold C. Robinson (Naval Undersea Warfare Ctr., tion, which is a measureof wave-numberfiltering through an outer New London Detachment, New London, CT 06320) alecoupler.The front of the first layer is exposedto turbulent flow and The variationalprinciple is an approximationmethod that allows the back of the last layer is in contact with static air. The resultspre- one to obtain accurateestimates of certain quantitiesusing relatively sentedhere are the numericallycalculated transfer functions and noise crudetrial functionsfor the physicalbehavior. This principleis applied reductionsachieved by variouslayers of elastomermounted on a steel to transduceranalysis by couplinga variationalprinciple developed for plate. the drivingelement (including piezoelectric effects) to onefor the shell. The motionof the transduceris, in turn, coupledto a variationalprin- ciplefor thesurface pressure in a fluidmedium. The modelingof a class 10:00 IV flextensionaltransducer will be presentedin detail. The in vacuo 4aEAS. A great depth class V flextensional transducer design. resonancefrequencies for the piezoelectricdriving stack and elliptical Michel Lctiche (Thomson Sintra ASM-525, Route des Dolines, shell,as well as the in vacuomode shapes for the driver-shellcombina- BP 157,06903 SophiaAntipolis Cedex, France) tion will be comparedwith existingtheoretical and finite-elementanal- yses.Variationally determined surface pressures for a singletransducer Flextensionaltransducers consist of a piezoelectricor magnetostric- will be presentedand comparedto finite-elementresults. Admittance tire driver and a mechanicalsheik The shell, excitedon its first bending plotsand beam patterns for thesingle element will be shown. [This work mode, amplifiesthe acousticradiation. In a first part, the coupling wassponsored by the Officeof NavalResearch.] betweenthe driver and the shell is analyzed. The relative resonance frequencyof eachelement determines the resonancefrequency of the transducerand its radiatedacoustic power. Furthermore, in mostcases, 9:30 operatingdepth is a significantlimitation in the designof this kind of source•classicalflextensional transducers on the work market are typ- 4aEA3. Broadband impulse transducer for measurement of baekseatterlngby objects in water. Christopher S. Kwiatkowski, icallydepth limited at about200 or 300 m. To avoidthe effectsof the hydrostaticpressure, mechanical filters have been developed. The aim of Gregory Kaduchak, and Philip L. Marston (Dept. of Phys., these devices is to make the driver and the shell independentunder WashingtonState Univ., Pullman, WA 99164-2814) static conditions. An equivalent schememodel is used to understand A broadbandimpulse pressure transducer was developedusing a and to design this filtering element. Theoretical results are presented 15X 15 cm sheet of PVDF in water. Both sides of the sheet were in and a great depth classV flextensionaltransducer has been developed

1831 d. Acoust. Sec. Am., Vol. 94, No. 3, Pt. 2, Sept. 1993 126th Meeting: AcousticalSociety of America 1831 using this original technology.Its acousticand static behaviorshave nesses,viscosities, etc.). Instead of integratingthe ODEs using the beenoptimized with an axisymmetricB.E.M./F.E.M. numericalcode. known drive, as would be done to predict the system'soutput, the ODEs Finally, theoreticalresults are discussedin comparisonwith experimen- are explicitly solved "backwards" given the desired output. This solu- tal onesobtained with the CERDSM facilitiesin Casfillon Lake. Finally tion typicallyrequires the accuratenumerical calculation of derivatives acousticperformances of this low-frequency,high power, and great as well as the point-by-pointsolution of simultaneousnonlinear equa- depthtransducer are shown.[Work supportedby DRET.[ tions. Techniquesfor the efficientsolution of the equationsas well as solubilityissues are discussed.[Work supportby Space& Naval War- 10:15 fare SystemsCommand.]

4oEA6. Three-dimensional modeling of low-frequency active source 11.•0 arrays. Donald L. Cox and Robert T. Chapman (Naval Undersea WarfareCtr., Div. Newport,Detachment New London,Code 423, New 4aEA9. A 350-m depth c•pable, air-compensatedbaffled transponder London, CT 06320) for the deep water portable tracking system. R. K. Menoche, R. J. Reid (Naval Undersea Warfare Ctr., Range Development Div., A three-dimensionalanalysis of two closelyspaced class IV flexten- Newport, RI 02841), and P. J. Stein (Scientific Solutions, Inc., sionaltransducers is present.ed.The analysiswas performedusing a Nashua, NH 03062) finite-elementprogram, NOMAD, developedto solve extremelylarge three-dimensionalproblems. The program NOMAD (NO •/[atrix De- This presentationdescribes the designand testingof a novelbaffled composition)uses the conjugategradient itemfive solution technique centralup-link subsurface link (SSL) for the deepwater portable track- with element by element (EBE) storageand preconditioningand en- ing system(PTS). The centralSSL is deployedat depthsup to 350 m hancedCmy vectorprocessing. In order to demonstratethe modeling and collectsthe acousticinformation from the bottom mooredtracking capabilitiesof the code,no symmetrydownsizing of the two transducer transponders.These transponderscan be deployedto depths down to modelwas invoked. Stress and flux densityinformation are providedfor 6000m. Degradationof the up-linkSSL performance is generallydue to the transducerresponse. For the acoustic media, both pressureand supportship radiatednoise and surfacegenerated ambient noise. These intensity information is presented.[Work supportedby the NUWC sourcesof interferencecan be suppressedwith a downwardlooking IR/IED program.] receiver.This receivermust have a wide beamwidth(140 deg) and its responsemust fall off rapidly outsidethe beamto rejectambient noise. The devicebuilt consistsof a hydrophoneand projectormounted on the 10'30 faceof a steelsignal conditioning plate (SCP). The plateis designedto 4sEA7. Understandingcoupling between flexural disk transducers havelow vibrationsensitivity. Behind the plate,and extendingbeyond from near field measurement. Jean-Marc Cortamberta) and Steven the SCP edges,is a fiberglassair chamber.To preventcrushing, it is fed R. Baker (Phys. Dept. Naval PostgraduateSchool, Monterey, CA by an air-compensationbag. Extensionof the air-backingbeyond the 93943) SCP is importantto ambientnoise rejection. This softsurface helps to rejeetnoise which diffmcts around edge of the battle.The air-chamber Both in civilian and military applicationsof underwateracoustics designwas chosen over materialsolutions because it wasuncertain if, at the needof high-power,directional low-frequency sources has stimu- the deeperdepths, the latter could providethe pressurerelease surface lated the developmentof volumetricarrays of closelyspaced transduc- required. ers. Understandingthe couplingbetween transducers in the array comesfundamental to proper beamformingin the active sonararray. 11:15 The paper presentsthe study of two flexural double bilaminar disk transducersby the method of finite elementsusing the ATILA code. 4sEA10. Reciprocity assessmentof single transducers. Li-Feng Ge The modification of the vibration behavior and the near-field radiation (Anhui Bureau of Technical Supervision,Hefei, Anhui 230001, distortionof an elementinduced by an adjacentelement are computed. People'sRepublic of China) The resultsare comparedwith the measurementof the displacementon the flexuraldisk usingsurface mounted strain gagesand the pressure Although most conventionaltransducers are usuallyregarded as field near the transducers.[Work supportedby the FrenchDelegation reciprocalat nominalsignal level, it is still necessaryto ascertainthat Generale pour i'Armement and the Naval PostgraduateSchool.[ the presumedreciprocal transducer is indeedreciprocal or possesses a)FrenchNaval Engineer. Permanent address: DeN Toulon/SDET/ sufficientreciprocity in reciprocitycalibration practice. A conventional BP77, Toulon 83000, France. reciprocitycheck involvesa systemcomprised of the two transducers andthe gaseous,liquid, or solidmedium and its boundaries.This paper triesto givean absolutemethod for reciprocityassessment without the 10:4S need of any other auxiliary transducer.The principleis that if the 4aEAg. Linearlzlng the output of nonlinear transducers by imaginary part of the electricalimpedance of a transducer(i.e., the preprocessingtheir input signals. S. E. Forsythe (Naval Res. Lab., capacitancefor piezoelectric-typeor the inductancefor electrodynamic- Underwater Sound Reference Detachment, P.O. Box 568337, Orlando, type transducers)varies linearly with its mass load impedance,the FL 32856) transduceris reciprocal.So, the linear correlafioncoefficient could be consideredas a reciprocityindex. The theoryis appliedto evaluatethe A techniquehas beendeveloped at USRD to drive transducersto reciprocityof a piezoelectricand an electrodynamic vibration generator. amplitudesat which nonlinearitiesin the output normally becomeevi- The coefficientsare determinedas 0.9915 (at 10 kHz) and 0.9773 (at 1 dent whilemaintaining the outputsignal as a faithfulcopy of the drive kHz), respectively.With the data processedby a complexleast-square- signal.This is done by preproce•ing the desiredsignal using a trans- fitting code[L.-F. Oe, J. Acoust.goc. Am. 91, 2326 ( 1992)], the rele- ducer model that includes the tmnsducer'snonlinearity. The model is vant coefficientsare adjustedto 0.9987 and 0.9724. Thereupon,the stated as a system of coupled ordinary differential equations (ODEs) transducerscan be regardedas reciprocalat their respectiveworking which definethe dynamicvariables of the system(positions, velocities, frequencies.The assessmenthas been verified by the accuratecalibration accelerations)as well as the parametersof the system (masses,stiff- results.

1832 J. Acoust.Soc. Am., VoL 94. No. 3, Pt. 2. Sept.1993 126thMeeting: Acoustical Society of America 1832 THURSDAY MORNING, 7 OCTOBER 1993 GOLD ROOM, 8:55 TO 11:45 A.M.

Session 4aMU

Musical Acoustics:Wind Instrumentsand Synthesisby Physical Modelling

DouglasH. Keefe, Chair Schoolof Music,DN-iO, Universityof Washington,Seattle, Washington98195

Clmir's Introduction--8:5S

Invited Papers

9:00

4aMUI. Two complexeffective lengths for air columns. R. Dean Ayers (Dept. of Phys.and Astron., California State Univ., Long Beach, CA 90840)

In the contextof a plane-waveapproximation for acousticwaves in an air column,the pressurereflection coefficient R is relatedto the relativeinput impedanceZ/Z c by a simplebilinear transformation.At any locationalong the air column,the complex effective length to an open, downstream end of an equivalent cylinder is defined as Lo -- (j/2k0)ln(--R), wherek 0 is the undamped propagation number, and that to a closedend is defined as Lc= (j/2ka)ln(R). The real partsof thesequantities are just the conventionaleffective lengths to the correspondingends, which have been used in the study of musicalwind inst•ments. The imaginaryparts incorporatethe effectsof dampingwithin the air columnand at its downstreamtermination. The commontheme here is a simpleextrapolation of interefing,damped plane waves, with k0 serving as an artificiallylarge attenuation constant. L c turnsout to be moreuseful than L 0 for analyzingthe brassinstruments JR. D. Ayers,J. Acoust.Soc. Am. Suppl.I •8, Sl63 (1990)], and an earliertreatment of undampedhorus made implicit use of a real L c JR. W. Pyle,Jr., J. Acoust.So•. Am. 57, 1309-1317(1975}]. This new treatmentis morerealistic, computationally simpler, and conceptuallymore straightforward.

9:30

4aMU2. Transientbehavior of time-domainwind instrument models. PeterL. Hockje (Dept. of Phys.,Univ. of NorthernIowa, Cedar Falls, IA 50614-0150)

An importantplaying characteristic of a musicalwind instrument is its transientresponse, which is wellsuited for calculation by time-domainmodels. Typically, the instrumentair columnis describedby a time-domainresponse (either impulseresponse or reflectionfunction), and a reed valveby a flow controlequation and harmonicoscillator dynamics. Since important musical effectshave beenobserved for changesin harmonicityof instrumentresonances on the order of 10 cents(0.6%), calculations intendedto showsuch effects need to specifythe instrumentresponse with appropriateresolution. In one calculationalexperi- ment,the air columnresonance frequencies are adjusted in the frequencydomain, then the correspondingtime-domain response is calculatedand the dynamicalmodel run. The resultsshow significant changes in transientresponse due to minorchanges in air columnresponse or in reedresonance. In additionto FFT methods,the transient behavior of spectrumpartials may be tracked by applyingthe Hilbert transform to individuallyfiltered harmonics and finding their instantaneous frequencies and amplitudes. Alternatively,a systemof nearlyharmonic oscillators with varyingphases, frequencies, and amplitudes may be fit to the transient waveform.Each of thesemethods has uniquebenefits and difficulties.

10:0o

4aMU3. Addingpulsed noise to a flute physicalmodel. C'hrisChafe (Ctr. for Cornput.Res. in Musicand Acoust.,Dept. of Music, Stanford Univ., Stanford, CA 94305)

Pulsednoise has been detectedin the residualof steadyflute tonesafter eliminationof purely periodiccomponents. LMS adaptivelinear periodic prediction was used to tracethe waveform through its slightperiod-to-period fluctuations. The predicted signalwas removed from the original leaving a breathysounding residual to examine.Noise pulses in musicaloscillators result from periodsynchronous gating of the drivingmeans. Bowed string instruments exhibit noise pulses arising from alternating stick-slipmotion, where noise is introducedonly when the string is slipping.Distinct pulses are also exhibited by thesaxophone in which the reed modulatesair friction. Flute noiseis more continuousthan in string or reed tones.Short time Fourier transformationof the residual signal reveals that pulses are present, but spectrally weighted toward higher frequencies. A physical modelof theflute incorporating a corresponding noise synthesis method is presented.Results of thesimulation are compared for pulsequality and effecton frequencyjitter.

10:30

4aMU4. The influenceof clarinet and saxophonereed responseson soundproduction. Douglas H. Kccfe (Schoolof Music, DN-10, Univ.of Washington,Seattle, WA 98195)and SergeWaeffier (Universit6du Maine,72017 Le MartsCedex, France) Performersof reed-drivenwoodwinds understand the importantrole that the reedplays in the productionof aesthetically expressivemusical sounds, yet the current status of musicalacoustics theory and experiment concerning the reed is ambiguous.

1833 J. Acoust.Soc. Am., Vol. 94, No. 3, Pt. 2, Sept. 1993 126thMeeting: Acoustical Society of America 1833 Benade(1976) stressedthe hnportanceof the reedresonance in controllingthe tuningand tone color of reed-drivenwoodwinds, and Thompson(1979) experimentallymeasured such tuning effects using a metal reed with a quality factor (Q) of about 10. However,the Q of a clarinetreed has beenreported to be about 3. Time-domainsimulations of a clarinetwith a Q of 3 did not showthe predic•l entrainmentof the playingfrequency to a subharmonicof the reedfrequency (Keefe, 1992). Measured responsesof moistclarinet and saxophone reeds using mechanical impact excitation have been obtained in a configurationin whichthe experimenter'sthumb applies the staticforce of the reedagainst the mouthpiece.This is intendedto mimicthe lower lip of the player under playingconditions. Results indicate •'s in the range of 5-10. Time-domainsimulations of sound productiondemonstrate that entrainmentcan oecorin thesehigher-Q regimes.

Contributed Papers

11:00 fundamentalfrequencies extending over a 2-octaverange. It was found that 10 spectralenvelopes, defined by amplitudesin eachof 24 standard 4sLMUS.Input responseof cylindrical and ennical bores with a single critical bandsspanning the frequencyrange 0 to 10 000 Hz, were suf- tone hole: Mensurements and predictions. Teresa Wilson and ficientto characterizethe tone set. Time-variantspectra were synthe- DouglasKeefe (SystematicMusicology Program, School of Music, sizedusing the originalrms amplitude-versus-timeenvelopes as driving DN-10, Univ. of Washington,Seattle, WA 98195) functionsto dynamicallyselect and interpolatebetween the appropriate There exist few measurementson the acousticalresponse of tone spectralenvelopes for eachmoment of time. The time-variantspectra holesin conical-boreair columns.For practicalapplication to wood- werethen converted into soundsignals using conventional additive syn- wind design,the accuracyof predictivemodels is saidto be insufficient thesis.Since the synthetictones sound almost identical to the originals, [McCann and Mathews,J. Acoust.Soc. Am. 91, 2449 (A) (1992)]. it appearsthat dynamicspectral envelopes are an importantdefining Experimentsperformed test the transmissionline modelof air columns characteristicof trumpet tone behavior. and tone holes. The input impedancewas measuredover the range 150-10 000 Hz for a singletone hole in a cylindricalbore and in a 11:30 conical bore. The cylindrical bore had length 920 mm and radius 7.2 ram, and the conicalbore had length630 ram, entry radius6.5 ram, and 4aMU7. An experimental investigation of the phase difference exit radius 12.5min. In woodwinds,the low-frequencyresonances con- between lip vibration and a•onsUc pressure in brass instrument trol the playingfrequencies. Hence, the resonancefrequencies under 1 mouthpieces.S. Yoshikawa (Fifth Res. Ctr., DefenseAgency, Japan) !ritz werepredicted from a modelof the air columnand tone hole.The and G. R. Plitnik (Univ. of Tsukuba,Tsukuba, Japan) measuredand predictedresonance frequencies for the cylindricalbore agreed to within 64.6 centsand for the conical bore agreed to within Over a century ago, Hclmholtz classifiedreed instrumentsas those 23 4.18 cents.The errorsin the conical-boretheory are largestat low which tend to blow closedas the blowingpressure increases (the me- frequencies.Work is underwayto refine the theory of tone holes in chanicalreed instruments),and thosewhich tend to open as blowing conical bores. pressureincreases (the lip reed instruments).All subsequentwork has tacitly assumedthat thesemodels are correct,and althoughmeasure- mentson clarinet-likesystems support the inward-blowingmodel, the 11:15 outward-blowinghypothesis has beenwidely usedas the basisfor the- 4•MU6. Dynamie spectral envelope synthesisof trumpet tones. oreticalmodels of the brassinstrument's sounding mechanism without JamesW. Beauchamp (Schoolof Music,Univ. of Illinois,2136 Music experimentalverification. As an alternatetheory, the hypothesisthat Bldg., 1114 W. Nevada, Urbana, IL 61801) and Andrew Homer the vibratinglips of a brassplayer may act as an inward-blowingreed (Hong Kong Univ. of Scienceand Technology, Kowloon, Hong Kong) hasbeen investigated. For this preliminarystudy, the phasedifference betweenlip vibration and acousticpressure was measuredin several It is well known that spectralenvelopes of brasstones vary with ditfcrentlip-driven devices: a cylindricaltube without a mouthpiece,a performeddynamic [D. Lace and M. Clark, J. Acoust.Soc. Am. 42, Frenchhorn mouthpiece coupled to a nonresonantpractice pipe, and a 1232-1243( 1967)].In thisstudy average spectral envelopes were com- trumpet.By meansof this experimentstudy, it is hopedthat a definite puted as functionsof normalizedinstantaneous rms amplitudeusing resolutionto the operatingmechanism for tbe vibratinglips of brass time-variantspectral data from a groupof 15 trumpetswell toneswith playerswill be etfected.

1834 J. Acoust.Soc. Am., Vol. 94, No. 3, Pt. 2, Sept.1993 126thMeeting: Acoustical Society o! America 1834 THURSDAY MORNING, 7 OCTOBER 1993 CENTURY ROOM, 10:15 TO 11:45 A.M.

Session 4aNS

Noise: ProgressReport on the ContinuingActivity Basedon the May 1993 Special Workshopon the ASA's Role in Noise and its Control

Robert M. Hoover, Chair Hooverand Keith, Inc., 11381Meadowglen, Suite 1, Houston,Texas 77082

Invited Paper

10:lS

daNSI. Progressreport on the continuingactivity basedon the May 1993 specialworkshop on the ASA's role in noise and its control. Robert M. Hoover (Hoover and Keith, Inc., 11381 Meadowglen,Ste. 1, Houston,TX 77082)

A discussionmeeting is beingsponsored by the TechnicalCommittee on Noiseto presentthe progressthat hasbeen made to dateon the recommendedactions that weredeveloped by the workinggroup participants of the May 1993Special Workshop on the ASA's role in noiseand its control.The resultsof the May workshopwill be summarized.Representatives of eachworking groupwill presenta discussionof the progresson specificinitiatives that havebeen begun. These will includeany collaborative actionsbeing taken with the cooperationof other Technicaland ASA StandingCommittees.

THURSDAY MORNING, 7 OCTOBER 1993 SILVER ROOM, 7:55 A.M. TO 12:15 P.M.

Session 4aPA

Physical Acoustics:Physical Acousticsfor Materials Characterization I

Leonard J. Bond, Chair Centerfor Acoustics,Mechanics, and Materials,University of Colorado,Boulder, Colorado 80309-0427

C!mir's Introductions7:55

Invited Papers

4aPAI. Acousticstudies of high-T½oxide superconductors.H. Ledbetter(Natl. Inst. of Standardsand Technology,325 Broadway,Boulder, CO 80303}

Variousacoustic studies of high-T½oxide superconductors, mainly cuprates, will be reviewed.Transition temperatures T½ rangefrom about20 K for the electron-conductor,(Pr-Ce) 2 CuOa , to about125 K for thalliumcuprate. Properties considered includesound velocities, elastic constants, attenuation, Debye characteristic temperature Oo, andGriineisen parameter. Variables consideredinclude composition, temperature, pressure, and magnetic field. Especially the polycrystals are complicated by defects suchas twins,voids, microcracks, nonhomogeneities, texture, and impurityphases. Even monocrystals are seldomdefect-free. Most studiesfocused on the YBa2Cu3Oxcompound, where x variesbetween 6 and 7. The bismuthcuprates behave differently frommost other compounds, perhaps because of incommensuratestructural modulations. No convincingevidence exists that the newsuperconductors show velocity-temperature or attenuation-temperature curves similar to conventionalBCS superconductors. This suggestsa mechanism different from the simples-electron spherical-fermi-surface weak-coupling BCS modal.However, the newmechanism involves phonons. A relationshipbetween T½ and Oo hasbeen established for four systems:La•), Y-O, Bi•), TI-O. Interrelationshipsamong acoustic properties and other physical properties such as thermal expansity and specific heat are emphasized.It is emphasizedthat someacoustic properties, especially the bulk modulus, can be estimated from simple models. Finally, topicsare recommendedfor further study.

1835 J. Acoust.Soc. Am., Vol. 94, No. 3, Pt. 2, Sept. 1993 126th Meeting:Acoustical Society of America 1835 8-.3O

4sPA2. Point-source/point-receiverultrasonies: A versatile materials characterizationtool. Wolfgang Sachseand Richard Weaver (Theor. and Appl. Mech., Cornell Univ., Ithaca, NY 14853-1503)

The essentialelements of a point-source/point-receiverultrasonic system include a broadbandwidth, small-aperture source generatingelastic waves with a broadangular spectrum and a receiverwith similarcharacteristics to detectthem. By movingthe sourceor receiverand stackingthe receivedwaveforms, one generatesa scanimage that providesa view of the completeelastic wave field in a testspecimen. Wave arrivalsare relatedto the speedsof propagationof variouswave modes in variousdirections and the signalamplitudes reflect the propagationalcharacteristics of the material.An interpretationof the scanimages requires an understandingof the propagationof transientelastic waves in a boundedstructure. Recent developments on both the forward and inverseproblems are summarizedand the full solutionof the forwardproblem for the responseof a geoeralaxisymmetric anisotropicvisecelastie plate is reported.The computedresults are comparedto measuredwaveforms in viscoelasticand trans- vetselyisotropic materials. Also reviewedare the approachesfor processingsingle wave forms and scanimages to recoverthe elasticand viscoelasticproperties of a testspecimen. Extensions of this approachto materialsof arbitraryanisotropy and layered microstructuresare also considered.[Work supportedby Cornell's Materials ScienceCenter (NSF) and the Office of Naval Research(Physical Acoustics and Solid MechanicsPrograms}.]

9.-OO

4sPA3. Ultrasonictomography for materialscharacterization. David A. Hutchins (Dept. of Eng., Univ. of Warwick, Coventry CV4 7AL, UK)

Ultrasonictomography may be usedas a methodfor imagingthe internalstructure of a wide rangeof solidmaterials. To do so requirestomographi½ reconstruction programs that can deal with irregulargeometries, acoustic raybending and the possible presenceof velocityanisotropy. Image reconstructiontechniques are now availableto deal with suchproblems, and havebeen appliedto severalsituations of interestto materialscharacterization. The first of theseinvolves the studyof samplesin bulk solid form, wherea scanningsystem involving sliding contact transducers has been used to collectultrasonic data and imagematerials thathave been subject to thermaleraeking. Additional studies have investigated the failure of fiber-reinforcedpolymer composites under applied load. In both cases,correlation with acousticemission (AE) data has been performed.Other work has used immersionand noncontact ultrasonic transduction to imagethe structureof thin platematerial using Lamb waves. In all cases, imageswill be presentedand conclusionsdrawn on the type of informationavailable from suchimages. [Work supportedby SERC.]

9-.8O

4sPA4. Ultrasonicnondestructive evaluation of a layeredmedium. V. K. Kinra, C. Zhu, P. Jamminet,and V. Iyer (Ctr. for Mech. of Composites,Dept. of Aerosp.Eng., TexasA&M Univ., CollegeStation, TX 77843-3141) This paperis concernedwith developinga techniquefor an ultrasonicdetermination of the acousticalproperties (thickness, wavespeed, density, attenuation) of the individuallayer in a layeredmedium. The layeredmedium is surroundedby an identical host medium (water} of infiniteextent on either side.Normally incidentplane longitudinalwaves are considered.Transfer functionshave been calculated in timedomain as well as in frequencydomain. A satisfactorycomparison between the theory and the experimentwas observed for a three-layeredmedium (forward problem}.An inverseproblem is definedas a simultaneous determinationof severalacoustic parameters from the measuredtransfer functions. A systematicanalysis of the sensitivityof the transferfunctions to the acousticparameters has been carried out. The followinginverse problems have been solved for a three-layeredmedium: three thicknesses for a three-layeredmedium; and wave speed and thickness of anyone of the layers(given thoseof the remainingtwo layers}.Finally, relativemerits of the time-domainand the frequency-domainapproaches have been studied.[Work supportedby TexasAdvanced Technology Program.]

10:00-10:15 Break

ContributedPapers

10:15 of thisbehavior has been simulated numerically by incrementallyvary- 4aPA5. Elastic guidedwaves and the Floquet conceptin periodically ing laminaproperties starting from a homogeneousaverage value. It is demonstrated that the transmission zones arise from a consolidation or layered plates. D. E. Chimenti (Dept. of Aeroeng. and Eng. Mech., Iowa State Univ., Ames, IA 50011), P. J. Shull (Johns Hopkins clusteringof the uniform-plateminima into frequencyzones or bands, Univ., Baltimore, MD 21218), and S. K. Datta (Univ. of Colorado, similar to Floquet wave behavior.Moreover, thesebands, and the as- Boulder, CO 80303) sociateddispersion curves, are approximatelyconstant in frequency, entirelyunlike the behaviorexpected for a homogeneousplate. It is This paperdescribes the resultsof experimentsand calculationson suggestedthat the largephase shifts induced in a layeredmedium com- the interactionof ultrasoundwith aluminum/aramid-epoxycomposites (ARALLm), a planar laminateof alternatingconstituent layers. The posedof elasticallycontrasting media are responsiblefor thisobserva- plateshave been investigated experimentally using fluid-coupled leaky tion. This mechanismalso leads to a correspondencebetween the num- wave techniques,and theoreticallyusing both a partial waveanalysis ber of reflectionminima and layer unit cells. The effectof structural andalso a stiffness-basednumerical approach. Frequency zones of wave symmetry on the reflectionfunction has also been studied.The theoret- transmissionand reflection, similar to thosepredicted for periodicme- icalpredictions compare very well, in nearlyevery case, to the experi- dia havebeen observed and modeledin the bilayeredplates. The onset mental results.

1836 J. Acoust.Soc. Am., VoL 94, No.3, Pt.2, Sept.1993 126thMeeting: Acoustical Society of America 1836 10-.30 11:15

$aPA6, Measurement of elustic properties of transverselyisotropic 4aPA9. Radiative transfer and multiple scattering of diffuse plates usingRayleigh=Lamb waves. Wayne P. Rogers(Dept. of ultrasoundin polycrystallinemedia. JosephA. Turner and Richard Mech. Eng., Univ. of Colorado,Boulder, CO 80309-0427) L. Weaver(Dept. of Theor.and Appl. Mech., 104S. WrightSt., Univ. of Illinois, Urbana, IL 61801 ) This paperpresents a novelmethod to experimentallydetermine the elasticconstants of a transverselyisotropic plate using measurements of A modelfor the multiplyscattered incoherent field in a continuous phasevelocity of Rayleigh-Lambwaves. The forwardproblem, i.e., to polycrystallineelastic medium is presented.Unlike a previousdevelop- calculatethe phasevelocity versus frequency curves given known elastic ment based upon energy and flux conservationconsiderations [J. A. constants,has been solvedby numericalsolution to the appropriate Turner and R. L. Weaver, J. Acoust. Soc. Am. 93, 2312 (A) (1993)] dispersionequations. The problemattacked here is the inverseproblem, for a mediumcontaining discrete random scatterers, the presentmodel i.e., to determinethe elasticconstants given experimental measurements hasbeen developed from the waveequation and first principles.Appro- of phasevelocity as a functionof frequency.These elastic constants may priate ensembleaveraging of the wave equationleads to Dyson and be foundby simultaneoussolution of fivedistinct dispersion equations Bethc-Salpeterequations that governthe mean Green'sfunction and correspondingto particular measurementsof phasevelocity and fre- the covarianceof the Green'sfunction, respectively. These equations arc quency.This approachyields accurate solutions provided that appro- expandedfor weakheterogeneity and equations of radiativetransfer are priate Lamb wavesmodes, frequencies, and platedirections are chosen. obtained.The resultis validfor attenuationsthat arc small compared to The experimentalmethod employsa pair of variable-angle-beam- wave number: a/k,•l. Polarization effects are included, as before, contacttransducers used in a pitch-catchmode with a harmonicwave throughfive elastodynamicStokes parameters, one longitudinaland phasecomparison technique to measurephase velocity over the fre- four shear.The theoryis appliedto a statisticallyhomogeneous cubic quencyrange of 30 kHz-I MHz. Resultsare presentedfor severaliso- polycrystallinehalf-space immersed in a fluidand illuminated by a plane tropicplates and for a unidirectional-continuous-giass-fiber-reinforcedwave. Results on the angularand temporaldependence of backscattered epoxyplate. The elasticconstants calculated using this inverseproce- intensityare presentedand comparedwith the predictionsof a single- dureare thenused in the forwardproblem in orderto compareexper- scatteringtheory. It is anticipatedthat thisapproach may be applicable imentalresults to theoreticalpredictions of thedispersion curves for the to microstructuralcharacterization through the study of the time, firstfew modes.[Work supportedby NASA---Langley.] space,ultrasonic frequency, and angulardependence of multiplyscat- teredultrasound in elasticmedia. [Work supportedby NSF.]

10:45 11'.30 4aPA7. High-resolution velocity measurements in the superconductingstate of the heavy fermion compoundUPt s. S.-W. 4aPAI0. Guidedwaves in a fluid-solidbiinyered plate. C. L. Yapura Lin, H. Zhang, M. Levy, Bimal K. Sarma (Phys• Dept., Univ. of and ¾. K. Kinra (Ctr. for Mech. of Composites,Dept. of Aerosp.Eng., Wisconsin, P.O. Box 413, Milwaukee, WI $3201), C. Jin, and D. lvi. Texas A&M Univ., CollegeStation, TX 77843-3141) Lee (Cornell Univ., Ithaca, NY 14853) Considera fluid-solidbilayer of infiniteextent with the x 3 axisper- Ultrasonicmeasurements have been used very successfullyin inves- pendicularto the bilayerand the materialaxes coinciding with the tigatingmulti-phase superconductivity in the heavyfcrmion compound x2, andx• axes.The fluid is assumedto be elastic(and isotropic)while UPt3. Further probingof the superconductingproperties in UPt3 de- the solidis assumedto be elasticand orthotropic(i.e., with nine inde- mandseven higher resolutionin both ultrasonicvelocity and attenua- pendentelastic constants). Consider a planewave propagating in thex• tion measorements.In order to achievethis, a newapproach was used directionwith the particlemotion confined to the x•-x• planeand plane in measuringultrasonic velocity and attenuation,in which a digital strainconditions in thex2 direction.There are sixboundary conditions: dynamiccontrol technique was utilized in the conventionalpulse-echo zero normal and shear stressesat the traction-free boundaries,zero method.With thisapproach, longitudinal ultrasonic velocity and atten- shear stressand continuity of normal displacements,and normal uationof frequenciesup to 450 MHz weremeasured on a singlecrystal stressesat the interface.The dispersionequation is obtainedby setting UPt 3 samplein the superconductingstate. The overallresolution in the the determinantof the resultingsix-by-six matrix to zero. Numerical velocitymeasurement is in the order of 0.1 ppm. This enablesus to resultsin the form of phasevelocity, group velocity, and modeshapes determinea complexsuperconducting phase diagram for UPt• with are presentedfor the caseof a water/graphite-epoxybilayer. Several unprecedentedaccuracy. Superconducting phase boundary lines were interestingfeatures are observedand discussed.The physicsunderlying tracedeven within the transitionwidth. The critical propertyof con- thesephenomena has been exploredby studyingthe mode shapesat vergingphase transition lines is thus determinedunambiguously. This (and in the vicinityof) the frequenciesof interest.[Work supportedby in turn providescrucial information for the understandingof unconven- TexasAdvanced Technology Program.] tionalsuperconductivity in UPt3. [Work at UWM supportedby ONR and at Cornell by NSF.] 11:45

11:00 4aPA11. Wavelet representationof the three-dimensionalanisotropic elastodynamicGreen's function. Vinod K. Tcwary and Christopher 4aPA8. Elastic constants and damping using ultrasonic resonance M. Fortunko (Mater. Reliability Div., NIST, 325 Broadway,Boulder, spectroscopy:Application to moancrystaland polyerystal copper. H. CO 80303) Ledbetter,C. M. Fortunko (Natl. Inst. of Standardsand Technology, A detailedknowledge of waveformsis requiredfor nondestructive 325 Broadway,Boulder, CO 80303), and P. Heyliger (ColoradoState Univ., Fort Collins, CO 80523) ultrasoniccharacterization of anisotropicmaterials. The waveformscan be calculatedin termsof the elastodynamicGreen's function of solids. Severalauthors used ultrasonic resonance spectroscopy to determine The traditionalFourier/Laplace transform methods are computation- a material'selastic-stiffness constants, the Voigt C O . Complementaryto ally inefficientfor three-dimensionalanisotropic solids since they re- theseare the out-of-phase C•,•, which give the complete elastic stiffness quirefour-dimensional numerical integration in the wavevector and the •,•--Cq+iC,•.Here, • measurementsforboth moancrystal andpoly- frequencyspace. A representationof the Green'sfunction has been crystalcopper arc reported.For the moancrystalcase, the • vary developedin termsof highlylocalized Huygens-type wavelets in which stronglywith the vibrational mode. And, when interpretedagainst a the Green's function is expressedin the spaceof slownessvectors rather vibrating-stringdislocation model, the • presentseveral surprises. For than that of wave vectorsand frequency.The wavelet representation thepolycrystal, the • aremuch lower and nearly independent of vi- requiresonly a one-dimensionalnumerical integration of simplefunc- bration mode. tions and thus savescomputational (CPU) time by a factor of about

1837 J. Acoust. Soc. Am., VoL 94, No. 3, Pt. 2, Sept. 1993 126th Meeting: AcousticalSociety of America 1837 1000 comparedto the Fourier transformmethod. A solutionof the forms.This computationalportion of the work seeksto mathematically tensorialelastodynamic Cauchy problem and calculationof the retarded represent ultrasonic waves propagating in a bounded, three- Green's function will be described in terms of these wavelets. Results dimensional,anisotropic hemisphere. An integralrepresentation for the will be presentedfor pulsepropagation in anisotropicsolids. exactsolution of the Christoffelequation for wavepropagation in an- isotropichemispheres is developedusing a wavelettransform developed 12:00 at NIST. This representationallows the computationof materialdis- 4aPAI2. Waveform-based ultrasonics in anisotropic hemispheres. placementsas a functionof both positionand time for a givensource. Eric S. Boltz,Vinod K. Tewary,and Christopher M. Fortunko (Natl. This wavelet is a functionof the slownessvector, rather than the wave Inst. of Standardsand Technol., Mater. Reliability Div., Boulder, CO vector,and is bettersuited to anisotropicsolids where the directionof 80303) energyflow is parallelto the slownessvector. The sourcecase consid- ered is pencillead break in the centerof the fiat sideof an anisotropic Conventional ultrasonic materials characterization methods rely hemisphere.Surface displacements are computedfor variousmaterials. heavilyupon measurementsof acousticwave velocitiesand amplitudes Where possible,comparison with previouswork and with experimental which are often ambiguous.Waveform-based ultrasonics, however, seeks to extract valuable information from the actual ultrasonic wave- data are presented.

THURSDAY MORNING, 7 OCTOBER 1993 DENVER ROOM, 7:55 A.M. TO 12:00 NOON

Session 4aSA

Structural Acoustics and Vibration: Acoustic Tailoring of Materials and Structures

Courtney B. Burroughs,Chair EngineeringScience and MechanicsDepartment, Pennsylvania State University,State College,Pennsylvania 16804

Chair's Introduction--7:55

Invited Papers

8.•o

4aSAI. Results of acoustic optimization of a point-driven, thin-shelled cube using the boundary element method. Daniel H. Kruger,J. Adin Mann, III, Amy Spalding,and Keith Holman (Dept. of Aerosp.Eng. and Eng. Mech., Iowa StateUniv., Ames, IA 50010)

The sound power radiated by a thin-shelledcube is calculatedfrom simulatedacoustic velocities (equal to the normal shell velocity) usingthe boundaryelement method (BEM) [K. A. Conefareand G. H. Koopmann,3. Vib. Acoust. 113, 387-394 (1991)]. Optimizationtechniques are thenused to predictvelocity distributions that resultin the minimumoutput sound power. In futurework, recommendationsfor the additionof passivenoise control materials will be definedon the basisof achievingthe calculatedoptimal velocity distribution that will resultin the minimumradiated sound power. These criteria are testedon a point-driven,thin-shefied cube in an artecholechamber. The normalshell velocity is measuredusing a laservelocimeter. Again, soundpower is calculatedand the optimalvelocity distribution is determinedusing the BEM. Accuracyof powerpredictions, basedon experimentalpower measurements and computationalexamples, as a functionof frequencyand vibrationpattern are studied.

8:25

4aSA2. Somestructural acoustic features of multilayercomposite plates. M. Kim and Y. F. Hwang (CardcrockDiv., Naval Surface Warfare Ctr., Bethesda, MD 20084-5000}

Thispaper discussed the propagationof freewaves and the vibroacoustie response of a multilayercomposite plate subjected to a point-forceexcitation. The dispersioncharacteristics for variousmodes of wavepropagation as a functionof geometrical configuration,elastic properties, and materialloss factor are discussed.Acoustic radiation into waterfrom a compositeplate subjectedto a pointforce acting on its dry (air) sidehas been evaluated. Numerical examples focus on a three-layer(elastic/ viscoelastie/elastie)sandwich plate with a varietyof differentelasti½/visc. oclastic material propottles (clantic constants, damping ) and thicknesses.The advantagesand disadvantagesof a sandwichplate as comparedto a homogeneousplate of equalflexural rigidity are also discussed.[Work supportedby ONR.]

8:50

4aSA3.An efficientmethod for designingquiet compositestructures via materialtailoring. JungBac Oh and Gary H. Koopmann (Ctr. for Acoust. and Vib., Penn State Univ., University Park, PA 16802) An efficientdesign method is successfullydeveloped for achieving structures that radiate minimum acoustic power ba•ed on a materialtailoring. First, the far-field acoustic power of a planarradiator is writtenas a quadraticexpression in terms of the Rayleigh-Ritzformulation. Second, a completeacoustic power design sensitivity is developedanalytically that is neededto find a searchdirection for the improved design. This analytical sensitivity significantly reduces computation time as compared to the

1838 J. Acoust.Soc. Am., Vol. 94, No. 3, Pt. 2, Sept.1993 126thMeeting: Acoustical Society of America 1838 finitedifference scheme and provides an exactdesign sensitivity information. The formulationsfor acousticpower and design sensitivityare coupled together within the numerical optimization code, CONMIN, to minimizeacoustic power radiated from a planarsurface subject to variousexcitation conditions via localthickness tailoring. The designof quietstructures for general conditions--harmonicpoint excitation, uniformly distributed harmonic acoustic loading, and randomacoustic loading--in the givenfrequency band is achievedsuccessfully. Results on varioustest cases show that thehybrid composite structure is the most promisingmaterial for minimizingradiated acoustic power. The optimum hybrid composite plate shows that the radiated acoustic powercan be reducedup to 10 dB on varioustest cases.

9:15

4aSA4. Optimization of acousticaltreatments with respect to dynamic complianceand static deformationunder load. Edward M. Kerwin, Jr., Nathan C. Martin, JeffreyA. Zimmer, and JeffreyA. Doughty (Bolt Beranekand Newman, Inc., 70 FawcettSt., Cambridge,MA 02138) Thispaper presents a method of organizinginformation on two importantperformance measures of an acousticaltreatment or elementwhose dynamic compliance and total displacement under static loading are of concern.The methodis simple but quite general,and allows one to selectthe optimumtreatment from a setof candidates,or to modifyand optimize a givencandidate. Thetwo nornmlized performance metrics are the unit-volumedynamic compliance q, anda unitthickness-deformation parameter V--e/q, whereE is the staticthickness strain underload. The optimizationprocess utilizes these unit-volume parameters under the assumptionthat the requiredtotal dynamiccompliance q•,• will be specified,although its numericalvalue neednot be known aheadof time. In this caseit followsthat Vis alwaysproportional to the total thicknessand total deformationunder load. In additionthe V--q presentationhas provenhelpful in developingphysical insight into the behaviorof variouscompliant treat- ments. [Work supportedby Office of Naval Research.]

4aSAS.Material tailoringof structuresto achievea minimumradiation efficiency. KooroshNaghshineh (Acoust.and Radar Technol. Lab., SRI International,333 RavenswoodAve., Menlo Park, CA 94025), Gary H. Koopmann,and Ashok D. Belegundu (Penn State Univ., UniversityPark, PA 16802)

A strategyis developedfor designingstructures that radiatesound inefficiently in light fluids.The problemis brokeninto two steps.First, given a frequencyand overall geometryof the structure,a surfacevelocity distribution is found that producesa minimumradiation efficiency. This particularvelocity distribution is referredto as the "weak radiator"velocity profile. A finite elementadaptation of the integralwave equation is combinedwith the Lagrangemultiplier theorem to obtainthis surface velocity distribution.Second, a distributionof Young'smodulus and densitydistribution is foundfor the structuresuch that it exhibitsthe weak radiator velocityprofile as one of its mode shapes.Extensive use of structuralfinite elementmodeling as well as linear programmingtechniques is madeto find this distribution.The resultis a weak radiatorstructure. When comparedto a structure with uniformmaterial properties, the weakradiator structural response is foundto exhibitlower wave-numbercontent in the supersonicregion. The effectof modaloverlap on the performanceof the weakradiator structures is foundto be negligible.The exampleof a simplebeam radiating in a rigidbaffle is usedfor the purposeof illustration.

10:05-10:20 Break

10:20

4aSA6. Compositecylinder cross section tailoring for radiated noise reduction. Colin P. Ratcliffe (Dept. of Mech. Eng., USNA, Annapolis,MD 21402-5008), Roger M. Crane, and Armando L. Santiago (NSWC, Annapolis,MD 21402-5067) This paperpresents the resultsof an ongoinginvestigation into the reductionof transmittednoise for underwatercylindrical structures.A reductionin the radiatedself-noise of cylindricalstructures, compared with the conventionallyutilized aluminum structures,was undertaken,investigating the use of compositematerials with varyingcross sections to meet the specified requirements.The crosssections investigated included several variations of a state-of-the-arttriple skin construction, along with monolithic,canstrained layer and a semi-debondedcross section. Cylinders have beenfabricated and tested,comparing the dynamicvibration properties of theforced vibrations in air of thecomposite scaled cylinders to thebaseline aluminum. The modal analysisdetermined mode shapes, natural frequencies, and damping loss factors. These were then tested in reverberantconditions underwater to assesstheir acousticalperformance. The in air and underwatertests were compared to identifysimilarities and differencesbetween force excitation and acousticexcitation. The comparisonshowed where in air testscan be usedas an aid to estimatingunderwater performance. The resultsalso highlightedwhere in air testsare inadequatefor predictingunderwater behavior.The effectof the cross-sectionaldesign for the tailoringof the acousticsignature will be discussed.

Contributed Papers

10:45 of the coating.By convertingacoustic pressure wave incident on the 4aSA7. Acoustic reflections from acoustically tailored coatingto high wave-numberpressure and shearwaves in the coating, non•omogeneousviscoelasfic coatings. Courtney B. Burroughsand the nonhomogeneitiesin the coatingconvert potentially reflected waves Kimberly L. Beach (EngineeringSci. and Mech. Dept., Penn State into nonreflectingwaves, thereby trapping the energyin the coating Univ., State College, PA 16804l where the energy is dissipatedby the internal damping in the coating. An analytic model for acousticreflections from nonhomogeneous Examplesare presentedto showthe sensitivityof acousticreflections viscoclastiecoatings is developed.The modelincludes variations in the from coatingsto the nonhomogeneousproperties and damping of the viscoclasticproperties of the coatingin directionsparallel to the surface coating material.

1839 J. Acoust.$oc. Am., Vol. 94, No. 3, Pt. 2, Sept. 1993 126th Meeting:Acoustical Society of America 1839 11.-0o 11:30

4aSA8. Structure-property relationships in polymer interpenetrating 4aSAI0. New fiber-reinforeed polyurethane composites as a soft networksfor use as broad band dampingmaterials. ChristopherS. sonar window. C. M. Thompson, R. Y. Ting (Naval Res. Lab.-- Coughlin,Mary Q. Samuels,and RodgerN. Capps (Naval Res. Lab., USRD, P.O. Box 568337, Orlando, FL 32856-8337), and L.M. Underwater Sound ReferenceDetachment, P.O. Box 568337, Orlando, Leimer (Texas Res. Int., Austin, TX 78733) FL 32856-8337} A new polyurethaneformulation has beendeveloped for useas the In the searchfor broadbanddamping materials, it is desirableto acousticalwindow for a soft sonardome. The polyurethaneis basedon havepolymers with a broadand high lossregion in shearor extension, a 3000 molecularweight difunctional polybutyleneoxyglycol (PBOG) coveringthe entiretemperature and frequencyrange of interest.Inter- softblock. In addition, a moderately high trifunctional PBOG was penetratingnetworks, IPN's, are materialscomposed of two or more added to increase the cross-linkdensity for improving the polymer crosslinkedpolymers intimately and irrevocablyintertwined. The re- toughness."Spectra," an extendedchain polyethylenefiber, was se- sultingdistribution of microenvironmentscan resultin a materialwith lected as the reinforcementfiber becauseit has excellent physical a high mechanicalloss broadened over that of either polymercompo- strengthand is low in density.The lower densityassists in matchingthe nent alone. Severalseries of polyurethane/epoxyIPN's have been pre- specificacoustical impedance of the compositeto that of sea water. pared for possibleuse as broadbanddamping materials. All IPN's Fiber loadingsup to 50% in thicknesswere used.Samples of this new showedapparent true IPN behaviorwith no or very smallscale phase compositewere fabricatedand their physicaland acousticalproperties separation.Dynamic mechanical analysis revealed that the temperature were evaluated.Insertion lossof the test panel was measuredin the of the losspeak may be variedover a wide temperaturerange with USRD ATFI facility. The materialwas found to be acousticallytrans- formulation.Further work hasfocused on incorporatinga moreflexible parentat theoperating frequency range, and physically resilient to high epoxycomponent and/or a plasticizer,and comparisonof viscoelastic impactloadings. behaviorto observeddamping in constrainedlayer structures. [Work supportedby ONR.]

11:45 11:lS 4aSAII. Development of a new rigid composite for high-frequency 4aSA9. Exploratory materials developmentfar towed array sensor sonarwindow applications. C.M. Thompson,R. Y. Ting (Naval Res. systems.Rodger N. Capps (U.S, Naval Res.Lab., Underwater Sound Lab•USRD, P.O. Box 568337, Orlando, FL 32856-8337), L.L. Reference Detachment, P.O. Box 568337, Orlando, FL 32856-8337) Jenkins, and C. C. Chiou (Texas Res. Intl., Austin, TX 78733-6201) Extendedtowed array sensor systems are usedfor geophysicalsens- ing and explorationin the petroleumindustry, and for detectionof Successfuloperation of high-frequencysonar arrays requiresan submersibleobjects in navalapplications. Many of the polymericmate- acoustic window that not only has a minimal interferencewith the rials consideredfor usein towedarray hoseseither did not possessthe acousticalsignal but also is sufficientlyrigid to protect the electronics necessaryaging and weatheringresistance; provided satisfactory self- from arctic ice penetration.Current designsof the window materials noiseperformance at highertemperatures but wereunacceptable in cold call for compositematerials of epoxy containingeither glassor Kevlar water; or experiencedchanges in self-noisethrough fill-fluid penncation reinforcements.Those compositeshave unacceptablyhigh insertion and chemical reaction. There has been a need to develop and evaluate lossesand beam pattern distortion.A new window material has there- new classesof elastomersfor useas hosewall materials.Array self-noise fore been developedbased on a bromine-modifiedepoxy resin. The performancecan also be improvedthrough proper selection of polymers soundspeed and the densityof the compositewere controlledby the for usein vibration isolationmodules for low-frequencytowline excita- brominecontent and by usinga soft microballon.The "Spectra"rein- tion. Thermoplasticelastomers offer significantadvantages over other forcementfibers were used for meetingthe strengthrequiremere. Finite- typesof elastomersin costand easeof processing.Results are presented elementcalculations shows that a three-layerstructure of 1:3:2Spectra/ for both conventionalelastomers and thermoplasticsto showhow these microballon/Spectracomposite design should optimize the impact materialscan be selectedfor the propercombination of Young'smod- strengthof the materialwhile maintainingthe acousticalperformance. ulus and internalloss, tensile properties, and weatherresistance, Samplesof this new compositewere fabricatedand their mechanical resistanceto swellingand permeationby seawaterand fill fluids,adhe- propertiesevaluated, including the Izod impactstrength. Insertion loss sionto reinforcingmembers, for fabricationand evaluationas acoustic of testpanels was measured in the USRD ATFI facility.The resultsof modules.Use of thermoplasticsfor vibrationisolation modules is also these tests will be presentedfor discussion.[Work sponsoredby discussed.[Work supportedby NAVSEA PM 0425.] NAVSEA.]

1840 J. Acoust.Soc. Am., Vol. 94, No. 3, Pt. 2, Sept. 1993 126th Meeting:Acoustical Society of America 1840 THURSDAY MORNING, 7 OCTOBER 1993 MAJESTIC BALLROOM, 9:00 TO 11:50 A.M.

Session 4aSP

SpeechCommunication: Current SpeechSynthesis Technology

JosephP. Olive, Chair AT& T Bell Laboratories,600 Mountain Aoenue,Murray Hill, New Jersey07974

Chair's Introduction---9:00

Invited Papers

9:05

4aSP1.Text normalizationand ambiguity resolution in speechsynthesis. David Yarowsky (Dept. of Compnt.and lnform. Sci., Univ. of Pennsylvania,Philadelphia, PA 19104)

Raw textcontains many ambiguities that must be resolved in speechsynthesis. Numbers and abbreviations often have different pronunciationsin differentcontexts, as in the phrase"1240 peopleat 1240St. AlbansSt." The token"IV" is pronounced differentlyin "Henry IV," "SectionIV," and "IV drug." Propernames, acronyms, and words with the samepart of speechmay alsohave context-sensitive pronunciations. Previous speech synthesizers have usedheuristics or simpledefaults to handlethese cases.In recentwork [Sproatet al., in InternationalConference on SpokenLanguage Processing (1992}], statisticaldecision procedureshave been applied to this text normalizationprocess. The talk will describefurther developments in this work, using Bayesiandiscriminators and decisionlists based on nearbywords, word classes,and type of text as evidencefor the selection betweenpronunciation variants. Examples will includeimplementations of thesealgorithms in the AT&T Bell LaboratoriesTTS synthesizer.

9:25

4aSP2. Text analysisfor speechsynthesis. Kenneth Ward Church (AT&T Bell Laboratories,600 Mountain Ave., Murray Hill, NJ 07974}

Text analysisis a catch-allterm for a rangeof taskssuch as tokenizing the input text into wordsand sentences,assigning parts of speechidentifying elities, parsing phrasal verbs, identifying and expandingabbreviations, dates, fractions, and amountsof money,and soon. Text analysisis importantfor speechsynthesis for two reasons.First, word pronunciationsometimes depends on usage:I can be a pronounor a Romannumeral, wind can rhymewith "bind" of '•inned," Dr. can be "doctor"or "drive," 2/3 canbe "two thirds"or "Februarythird," or "two slashthree." A second,equally important reason for text analysisis that its resultswill be usedto modulatethe pitch, timing,and amplitudeof the speechso as to presentthe text'smessage dearly. For example,the functionword "that" shouldbe cliticized(reduced) in certainusages (e.g., as a subordinatingconjunction: "It is a shamethat [schwa]he is leaving")but not in otherusages (e.g., "Did yousee THAT [no schwa]?"). If a synthesizercould reliablymake such distinctions, it mightsound a little morelike it knowswhat it is talkingabout (and that it cares).

9:45

4aSP3. Prosodicvariation for text-to-speechsynlhesis. JuliaHirschberg (AT&T Bell Labs.,Rm. 2D-450, 600 MountainAve., Murray Hill, NJ 07974}

Appropriateintonational variation is critical for text-to-speechsynthesis to conveyappropriate meaning and improvenatu- ralhesS.While in the past it has been thought that a full linguisticanalysis is prerequisiteto the generationof appropriate intonationalfeatures, in recent years considerableprogress has been made in assigningprosodic variation in text-to-speech synthesisfor unrestrictedtext, usingsimple and currentlyavailable techniques for text analysis.Techniques for varyingpitch range,prominence, and phrasing based on suchtext analysis will bediscussed. Also discussed will betechniques, such as phrasing andaccent assignment procedures. Such automatic training allows quicker development of newprosodic variation procedures and alsoallows such procedures to be tailoredto particularspeaking styles or applications.

10:05

4aSP4. GEST: A computationalmodel of speeehproduction using dynamically defined artieulatory gestures. CatherineP. Browman,Louis Goldstein, Elliot Saltzman,and PhilipE. Rubin (HaskinsLabs., 270 CrownSt., New Haven,CT 06511} A computationalmodel of speechproduction that producesspeech for Englishutterances, using dynamically defined artie- ulatorv gestures.will be described.The model is comprisedof three submodels.The first part, the linguisticgestural model, generatesa gestural score specifying the identity and relations of thegestures involved in thedesired utterance. This gestural score is inputto thesecond part, the task dynamic model [e.g., Saltzman and Munhall ( 1989}],which generates the movements of the variousmodel speech artieulators. These movements serve, in turn,as input to the third part,the vocaltract model [Rubin et al. { 1981)], whichdetermines the resulting area functions and acoustic signal. Attention will befocused on the integrated system and the firstpart, sincethe secondand third partsof the modelhave been described elsewhere.

1841 J. Acoust.Soc. Am., Vol. 94, No. 3, Pt. 2, Sept. 1993 126th Meeting:Acoustical Society of America 1841 10:25

4aSPS. Segmentalaspects of speechsynthesis. Marian Macchi (Speech SystemsRes. Dept., Bellcore,445 South St., Morristown, NJ 07960)

A phonemicsegment has differentacoustic-phonetic realizations depending on many contextualfactors, e.g., nearbypho- neroesand positionin the syllable,word, and phrase.Appropriate acoustic variation in the phonemesis necessaryfor intelligible, natural-soundingsynthetic speech. Two basicapproache• to achievingthese variations are: (1) articulatorysynthesis, which modelsthe humanvocal apparatus, attempting to automaticallyaccount for the desiredacoustic variability and (2) acoustic synthesis,which bypasses the articulatorylevel and operateson acousticpatterns directly, either by controllingphoneme-based format targetsand transitionsor by concatenatingprerecorded units. In a phoneme-basedsystem, whether articulatory or acoustic,the necessaryacoustic variations for eachphoneme are producedentirely by ruleswhose goal is to capturelinguistic and artieulatoryregularities. However, knowledge of theserules is incomplete.The rationalefor coneatenativesystems is that by recordingand storing multiple variants of eachphoneme, or unitslonger than phoneroes, the unitsthemselves incorporate some of the acousticvariation. Basic units for concatenationrange in sizeand phoneticnature from phoneroesor allophones,through dyadsor diphones,polyphones, and demisyllables, to units covering polysyllables or words. This talk discusses interactions among the modelingapproach, the basicunit, and the rulesfor combiningunits.

10:45

4aSP6. New directionsfor researchon the perceptualevaluation of syntheticspeech. David B. Pisoni (SpeechRes. Lab., Dept. of Psychol.,Indiana Univ., Bloomington,IN 47405)

A reviewof previousreo•areh on the perceptualevaluation of syntheticspeech produced by rule revealsthat moststudies have focusedon behavioralmeasures of segmentalintelligibility of isolatedwords. For the mostpart, exceptfor a few isolatedstudies, researchon sentenceprocessing and comprehensionof longpassages of fluentspeech has received very little attention.This is not surprisingbecause these are areasof researchin spokenlanguage processing that are difficultto studywithout the investmentof time and energyin developingnew methodologies that go well beyondphoneme perception and isolatedword recognition.Studies of prosodyand the role of naturalnessin intelligibilityand comprehensionare neededat this time to quantifythe contributionof thesesources of knowledgeto spokenlanguage processing. In this presentation,some of the recentstudies from this laboratory that have attemptedto measurethese more complexprocesses will be reviewed.Studies using a sentenceverification task and severalon-line measuresof comprehensionwill be described.Other methodsneed to be developedin the future to study intelligihility,comprehension, and retentionof syntheticspeech. [Work supportedby NIH ResearchGrant No. DC00111-17.]

ContributedPapers

11.'05 TRACTTALK simulatesthe vocal-tractsystem in the frequencydo- mainand derivesthe time-domainequivalent to producesound output. 4aSP7. An algorithm for generating phrase boundaries for the It incorporatesall importantcomponents of the systemand decomposes automaticassignment of prosodiccontours in a text-to-speechsystem thetransfer function into its zero and pole parts. Such a decomposition for Spanish. Helen E. Karu (Dept. of Linguist.,Georgctown Univ., enablesone to accuratelyestimate poles and zerosof a nasalizedsound. Washington,DC 20057-1068) First, temporaltrajectories of poles/zerosare examinedas a functionof Determiningphonological and intonationalphrase boundaries is an the velopharyngealopening, the presenceof the nasalsinuses, and other importantstep in synthesizingnatural-sounding prosodic contours in a articulatoryparameters. This is in follow-upto previouswork [Flana- text-to-speech(TTS) system.An algorithmis presentedhere that gen- gan, AT&T Bell Labs. internal report (1983)]. The attempt is to sys- eratesphrase boundaries in Spanishtexts. The basisfor this algorithm is tematically characterizethe pole/zero pattern of nasalizationfor im- Libermanand Church'sfunction group (f-group) parserfor English proving the performanceof formant tracking and feature labeling [M. Y. Liberman and K. W. Church, "Text Analysisand Word Pro- algorithms. Secondly, synthesisof nasalization is describedusing nunciationin Text-to-SpeechSynthesis," in Advancesin SpeechSignal TRACTTALK. Listeningexperiments are conductedto assessthe re- Processing,edited by S. Furui and M. M. Sondhi (Marcel Dekker, New lationshipsamong perceived nasality, inclusion of the nasalsinuses, and York, 1992), pp. 791-831].The Spanish•group parserproduced sat- the degreeof the velopharyngealopening. It is found,e.g., that inclusion isfactoryresults for shortersentences and sentencescontaining a fair of the nasal sinusesresults in strongerperceived nasality. While the amountof punctuation,but the parsertended to overgeneratephrase literaturereports differing views on the role of sinusesin nasality,these boundariesin longersentences and sentenceswith little punctuation.In resultsare consistentwith the findingsof Maeda [Proc. ICASSP 2, addition,the parsergenerated but did not distinguishdifferent types of 911-914 (1982)]. Syntheticspeech generated from the vocal-tractsys- sentenceand paragraphtransitions. To refinethe parserin theseareas, tem will be demonstrated. selectionsfrom a Spanishtext [E. Sabato,E! tt•nel (Editorial SeixBar- ral, Barcelona,1982)] were read by adult native Spanishspeakers and analyzedfor phraseboundaries as evidencedby significantchanges in 11:35 fundamentalfrequency, tempo, and/or pauses.The acousticphonetic 4aSP9. A diagnostic text-to-speech intelligibility test. Ann K. data and its role in the developmentof the phraseboundary algorithm Syrdal (AT&T Bell Labs., Rm. 3E-525, 101 Crawfords Corner Rd., are discussed. Holmdel, NJ 07733) and Beki A. Sciacea (AT&T Bell Labs., Naperville,IL 60566 and NorthwesternUniv., Evanston,IL 60208)

11:20 A widersampling of speechsegments and contextsis requiredfor 4aSPS. Acousticsand synthesisof nasalization. QiguangLin, James adequatelyevaluating text-to-speech output than is typically used in Flanagan,and ChiWei Che (CAIP Ctr., RutgersUniv., Piscataway, standardintelligibility tests of human speech.The test developedex- NJ 08855-1390) pandedupon both the DiagnosticRhyme Test (DRT) [W. D. Voiers, SpeechTech. (Jan/Feb.), 30-39 { 1983)] and a TTS intelligibilitytest In this paper acousticsand synthesisof nasalizationis studiedbased developedby van Santen[J.P. H. van Santen,Comp. Speech Lang. 7, on a comprehensivecomputer model of the vocaltract: TRACTTALK. 49-100 (1993)]. The featuralsystem. used to constructthe testensured

1842 J. Acoust.Soc. Am., Vol. 94, No. 3, Pt. 2, Sept.1993 126thMeeting: Acoustical Society of America 1842 that the mostlikely perceptualconfusions were potentialtest items. tences(e.g., "Happy mimes dance the book.")and were controlled for One- and two-feature contrastswere testedin word-initial, word-medlal, familiarityand verbtransitivity. Testing was automated and conducted and word-finalpositions, in stressedand unstressedsyllables. Vowel, interactivelywith individualsubjects who receivedno feedbackon their consonant,and consonantcluster contrasts plus insertionsand deletions performance.Results indicate the test was a usefuldiagnostic tool as were tested.Test items were presentedin semanticallyanomalous sen- well as evaluationtechnique.

THURSDAY MORNING, 7 OCTOBER 1993 COLUMBINE ROOM, 7:55 TO 11:30 A.M.

Session 4aUW

Underwater Acoustics:Signal ProcessingI

Peter H. Dahl, Chair •lpplied ResearchLaboratory, Unioersity of Washington,Seattle, Washington98105

Chair's Introductions7:55

ContributedPapers

8:00 low water environment.[Work sponsoredby the Officeof Naval Re- search,Program Element 61153N, with technicalmanagement pro- 4aUWI. Internal waves and matched-fieldprocessing. Darrell R. videdby NRL-SSC.] Jacksonand Terry E. Ewart (Appl. Phys. Lab., Collegeof Oceanand Fishery Sci., Univ. of Washington,Seattle, WA 98105)

The performanceof matched-fieldprocessing is degradeddue to 8:30 randomnessof the propagationmedium. With a vertical array, this degradationtakes the form of fragmentationand wanderingof the peaks 4aUW3. Trends in signal loss due to reflectingirregular bathymetry (mainlobeand sidelobes)in the range-depthambiguity surface. The in matched-fieldprocessing. James F. Smith (Acoust. Div., Naval resultingerrors in localizationare characterizedin termsof the rms Res. Lab., Washington,DC 20375) processoroutput. Simulations and theoryspecialized to the ew Bartlett Simulationsof the potentialof matched-fieldtomography for invert- processorare used. First, the case of an ocean waveguidewith a ing oceansound-speed structure (Tolstoy and Diachok, 1991) have to quadraticaverage sound-speed profile and verticallystationary sound- date neglectedeffects of bottominteracting modes. A studyto deter- speedfluctuation statistics is examined.Next, approximationsare intro- mine the effect of bathymetry in the thinly sedimentedPacific on ducedso that a relativelysimple analytic model can be abstractedfrom matched-fieldprocessing has been conducted.A range- and depth- the theory.This modelis cheekedagainst Monte Carlo PE computa- dependentsound-speed field was used.The acousticfield usedas syn- tions that avoid someof the simplifyingapproximations. The simple thetic data "measured"at the array was calculatedby the parabolic modelcontains scaling rules for processorperformance as a functionof equationprogram FEPE (Collins, 1991). The programwas shown to be frequency,array length, and medium vertical correlationlength. In highly accuratein matched-fieldstudies against "exact" resultspro- general, the effectsof internal waves becomemore important as fre- duced by the normal modesprogram KRAKEN (Porter, 1991). The quencyincreases, array length increases, medium correlation length de- effectsof irregular bathymetryand shiftsin bottom soundspeeds were creases,and range increases.The processoris predictedto be most studiedthrough simulationsconducted over extensiverange and fre- sensitiveto internal-wavemismatch for sourcesthat are in convergence quencyintervals. The resultsshowed an increasein signalarray degra- zones.Finally, the analyticalmodel is comparedto Monte Carlo PE dation with increasingrange and frequencyand reducedsource local- computationsusing oceanic realizations obtained from a realisticdy- ization. Effects of interaction with far and near sides of seamounts namic internal wave model. (relative to array position),and the overall trend of signalloss with rangedue to multipleinteractions with the bottomwill be discussed. 8:15

4aUW2. Sector-focused matched-field inversion for enhanced 8:45 environmental parameter estimation with reduced sensitivity to measurementerrors. Howard A. Chandler, C. Feuillade, and G. B. 4aUW4. Optimal detection and source localization in an uncertain, Smith (Naval Res. Lab., StennisSpace Center, MS 39529-5004) shallowwater environment. J.A. Shoreyand L. W. Nolte (Dept. of Elec. Eng., Box 90291, Duke Univ., Durham, NC 27708-0291} Sector-focused matched-field localization has been shown to effec- tively enhancerange-depth resolution while remaininginsensitive to An optimala posterioriprobability approach to matched-fieldpro- environmentalparameter mismateh. This becomesevident in parameter cessingis implementedusing the optimumuncertain field processor spaceambiguity functions where the responseis broadand therefore (OUFP} [A.M. Richardsonand L. W. Nolte, J. Acoust.Soc. Am. 89, insensitiveto mismatch. For source localization, this is a desirable re- 2280--2284(1991)]. CombiningMonte Carlo techniqueswith this pro- sult. However,for environmentalinversion, greater resolution may be cessorresults in a fast, efficientmethod for sourcelocalization or envi- desiredin parameterspace while remaininginsensitive to other mea- ronmentalparameter estimation when the environmentalparameter surement errors. This may be aecomolished by including. in the search searchspace is large. Detectionand localizationperformance is pre- sector,replicas derived from a set of "neighboring"environmental pa- sentedusing the ROC for detectionand the LROC (localization re- rameters.The purposeof this study is to investigatethe useof sector ceiver operatingcharacteristic) for sourcelocalization. Specific results focusingto increaseresolution in environmentalparameter space while are presentedfor a shallow water environmentas a function of signal- mitigatingagainst measurement uncertainty. Results will be presented to-noiseratio and environmentaluncertainty. [Research supported by usingthe KRAKEN normalmode model to simulatea canonicalshal- ONR under Contract No. N00014-91-J-1448.]

1843 J. Acoust. Soc. Am., Vol. 94, No. 3, Pt. 2, Sept. 1993 126th Meeting:Acoustical Society of America 1843 9:00 significant(5 to 12 dB) gainscompared to operationalsonar systems and other adaptive processingmethods. The Fourier integral method 4aUWS. Environmental source tracking using measuredreplica fields. (FIM} (Nuttall and Wilson, 1990) was thought to be the "spikiest" W. A. Kuperman,• Michael D. Collins,John S. Perkins,Laurie T. solutionto the IBF integralequation, that is also linear in the covari- Fialkowski, Timothy L. Krout (Naval Res. Lab., Washington, DC ancematrix. A standardinverse technique (Backus and Gilbert, 1968) 20375), Lindsay Hall, Ralph Marrett (Defence Scientific usedin tomographyhas recently been applied to the IBF integralequa- Establishment,Auckland, New Zealand), Lesley J. Kelly, Ashley tion, and two new theoretical results have been obtained. First, the Lamson (DefenceScience & TechnologyOrganisation, Salisbury, SA, plane-wavesolution, called the least-squaresWilson integralmethod Australia}, and John A. Fawcett (Defence Research Establishment (LSWIM), agreeswith FIM only at the array designfrequency, and is Pacific, Victoria, BC, Canada) spikier or more "delta function like" than FIM below array design Preliminaryresults will be presentedfor TESPEX (Test of Environ- frequency.Second, the non-plane-waveor matched-fieldsolution was mentalSignal Processing Experiment), which was performedin May obtainedby allowing the measureddata vector (eovarianeematrix) in 1993off the eastcoast of New Zealandin a regionof three-dimensional the Backus-Gilbert inverse method to have two discrete indices instead bathymetryvariations. This complexenvironment was exploited to min- of the usualone index. This work wasperformed during the analysisof imizeambiguity in environmentalsource tracking with a singlereceiver OutpostSUNRISE data for the purposeof enhancingsonar detection [Collinseta/., J. Acoust.Soc. Am. 90, 2366 (1991)]. To overcome and trackingperformance, but has alsoa more generalapplication in limited knowledgeof environmentalparameters, the acousticfield was acousticaloceanography. [Work supported by AEAS.]a•On temporary measuredby a fixed array of receiverswhile a ship towing a source leavefrom NeptuneSciences, Inc. sweptover a sector.The receiverswere linked to a recentlydeveloped satellitetelemetry buoy that transmittedtime series to a centralized 10:00 computerfacility for real time analysis.Expensive ship time wastraded off for cheapcomputation time by interpolatingthe acousticfield using 4aUWg. Extraction of both bottom backscattering strength and a WKB representationthat permitsa sparsesampling in azimuth.The reflection loss by inversion of reverberation measurements. Sicco D. main computationaltask for the data basinginvolves solving a nonlin- Kamminga?Dale D. Ellis,and Peter Gerstoft (SACLANT Undersea ear optimizationproblem for the WKB amplitudeand phasefunctions, ResearchCtr., Viale San Bartolomco400, 19138La Spezia,Italy} which vary slowly with rangeand azimuth. TESPEX data have been A methodis describedto simultaneouslyextract the bottom back- used to perform environmentalsource tracking using replicascon- scatteringstrength and bottomreflection loss as a functionof grazing structedfrom the acoustic field data base. alPresent address: Scripps angle from measurementsof monostatiereverberation. The least- Institutionof Oceanography,La Jolla,CA 92093. squaresdifference between a parametrizedmodel and datais minimized with respectto the parametersusing generic algorithms or simulated 9:15 annealing.The reverberationdata are from broadbandsources and om- 4aUW6. Oceanic tomography using model-based matched-filter nidirectionalreceivers deployed at a fiat-bottomeddeep-water area in processingof widebandacoustic signals. J.-P. Herinand (SACLANT the Mediterranean.The reverberationmodel is simple:the propagation UnderseaRes. Ctr., Viale San Bartolomeo,400, 1-19138 La Spezia, is describedby straight-lineray paths(although the effectiveangles are Italy} and W.I. Roderick (Naval UnderseaWarfare Ctr., Newport, correctedfor the sound-speedprofile); and parametrizedfunctions are RI 02841 ) usedfor the bottomscattering strength and reflectionloss. The param- eterscan alsoinclude the waterdepth, sound speed and gradient,source As originallyconceived, ocean acoustic tomography relies on deter- level, and pulselength. Where they can be compared,the parameters mining the travel timesof pulsesthat propagatealong identifiablemul- resultingfrom the inversionshow good agreement with the measured tipathsbetween pairs of transducers.In principle,other propertiesof ones,leading confidence to the procedure.As well, whenthe resulting acousticpropagation such as amplitude and phaseover a broad fre- parametersand actual sound-speed profile are input to the genericsonar quency band can be used to infer environmentalparameters. These model,the calculatedand measuredreverberations are in goodagree- parametersinclude range-dependent sound-speed profiles and geoacous- ment.a)Currently at Rijkswaterstaat, P.O. Box 3006, 2280MH Rijswijk, tie parametersof the seabottom. Recentexperimental work has dem- The Netherlands. onstratedthat the distortionof time-dispersedwideband signals can be compensatedeffectively by using a model-basedmatched filter 10:15 (MBMF). A multi-channelMBMF receiverthat incorporatesthe mod- eledOreen's function of the medium,determined the correctrange and 4aUW9. Track-before-detectmatched-field processing. Paul A. depthof the sourceand receiver. In thispaper, the possibilityof apply- Baxley (Ocean and AtmosphericSCi. Div., Code 541, NRAD, ing model-basedmatched-filter processing to the tomographicinversion NCCOSC, San Diego, CA 92152-5000}, Robert Bruce Williams problemwas investigated. The acousticdata are low-frequency,large (NRAD, NCCOSC, San Diego, CA 92152-5000),and William H. time-bandwidthproduct, linear-frequency-modulated signals transmit- Hodgkiss (ScrippsInst. of Oceanogr.,San Diego, CA 92152-6400) ted througha range-independentwaveguide at a deepwater site westof Sardinia.Compared to time-of-flighttomography, the amplitudeand Matched-fieldprocessing (MFP) is well-suitedfor trackingapplica- phasedistortion undergone by the propagatedwaveforms were fully tionsbecause of its inherentsource localization capability, as demon- exploitedto reconstruct,in part, the range-averagedsound-speed profile stratedby Wilmut et al. [J. Acoust.Soe. Am. 93, 2374 (A} (1993}]. If betweensource and receiver.This wasachieved by searchingfor the set exacttrack determinationis not an objective,improved detection at a of sound-speedprofile parameters that maximizedthe gainat the output low signal-to-noiseratio may be obtainedusing a simpletrack-before- of a multi-channel MBMF receiver. detect technique that averagesrange-shifted MFP ambil•uity-aurfaee snapshots,with the rangeshift beingdetermined by an assumedrange rate. After searchingthrough all candidaterange rates, the signalfunc- 9:30-9:.45 Break tion is approximatelyreconstructed in the averagesurface correspond- ing to the correctrange rate. If peak-to-sideloberelationships in the 9.-45 signalfunction vary little betweensnapshots, both the sidelobesand the 4aUW7, The tomographicinverse beamforming {TIBF} solutlon---A mainpeak are maximizedin theaverage surface for thecorrect range new matched-fieldalgorithm. JamesH. Wilsona) (Dept. of rate; otherwise,only the main peak is maximized.In either case,this Oceanogr.,Naval PostGraduate School, Monterey, CA 93943} maximizationprovides a detectionclue along with an estimateof range rate. This detectionenhancement at low signal-to-noiseratios is dem- The recent at-sea,real-time signal detectionand tracking perfor- onstrated via simulations for a 48-element full-water-column vertical manceof the plane-wavesolution to the inversebeam forming (IBF) array in a thickly sedimentedshallow-water environment (500-m water integralequation (Wilson, 1983;Nuttall and Wilson, 1990} has shown depth) typical of the southeasternMediterranean sea. A 50-Hz source

1844 J. Acoust.Soc. Am., Vol. 94, No.3, Pt. 2, Sept.1993 126thMeeting: Acoustical Sociely of America 1844 movingat constantrange rate and sourcedepth was simulated using a sightinto the similaritiesof a trainedneural network and a classical normalmode program, while noisesamples were obtained using a PE- qatched filter. basedshipping noise model and the HITS II shippingdistribution da- 11:00 tabase. 4aUWI2. Towed array processingas a spatial Kalman filter problem. 10:30 E. J. Sullivan (Naval UnderseaWarfare Ctr., Code 103, Newport, RI 02841) and J. V. Candy (Lawrence Livermore Natl. Lab., 4aUWI0. Acoustic signaturesof imploding underwater light bulbs. Livermore, CA 94550) William J. Marshall,Jr. (BBN Systems& Technol.,Union Station, New London, CT 06320) A movingtowed array essentially constitutes a system intended to providea seriesof measurementsthat are sequential in space.This type Implodinglight bulbs are sometimesused as underwatersound of processfits quite naturally into an iterativemeasurement process that sourcesbecause t ey prodt,ce impulsivesignals similar to smallexplo- can be realizedas a spatialpredictor-corrector form of a Kalman filter. sions,yet are cb -)er and more convenientto procure,store, and use. It is shownhow this conceptis formulatedand constitutesa generali- On a recentse, , 4al, light bulb sourceswere usedto' measurethe zationof the overlap-correlatorsynthetic aperture algorithm [E. J. Sul- straightnessof z. •. •ttom-mountedhydrophone array. For this purpose livan and S. Stergiopoulos,J. Acoust.Soc. Am. 86, 158-171 (1989)]. the sharp leadin• edge was the most important characteristicof the Exampleswill be giventhat demonstratehow this schemeconstitutes a acousticsignature, however the test provided a good opportunity to self-consistentsynthetic aperture algorithm capable of determininges- recordand studyother signature features as well. Resultsfor a moderate timatesof the bearingsof multiple sources,both correlatedor uncorre- numberof commonhousehold light bulbsare given. Data includesta- lated.It will alsobe shownhow the methodprovides coherent synthetic tisticson crushdepths, measured acoustic waveforms, and energyspec- apertureprocessing over integrationtimes that are significantlylonger tral levels,and correspondence between these observations and a simple than the coherencetime of the sourcesignals. theoryof soundgeneration by implodinggas bubbles. This information shouldbe usefulto othersplanning acoustical tests using such sources. 11:15 [Worksponsored by the AdvancedResearch Projects Agency.] 4aUW13. Scattering function descriptionof a shallow water channel.

10:48 Peter G. Cable (BBN Systemsand Technol., Union Station, New London, CT 06320-6147) 4aUWll. Insight into the learning processof neural networks for The shallowwater channelis consideredas a random,time-varying clussifyingacoustic signatures. Fred C. DeMetz, Sr. (Allied Signal linear filter. The sourcesof temporalvariation of channelproperties Ocean Systems,Inc., 15825 Roxford St., Sylmar, CA 91342) and considered are source and receiver motion and the motion of the surface LowellW. Brooks (Technol.Service Corp., P.O. Box 1120,Salida, CO (that is, wind wavesand ). Usingan energyflux descriptionfor 81201 ) acousticpropagation, after Smith, Weston, and Brekhovskikh, and em- Feedforwardnetworks employing the backwardpropagating delta ployingSmith's theory of coherencein multimodepropagation, an ex- rule for errorcorrection were tested utilizing simulated target signatures plicitformulation of thescattering function for a shallowwater channel andnoise to provideinsight into the network learning process. Network hasbeen obtained. The scatteringfunction description seems suited to a traininghistories and weightevolutions were studiedfor alternating mid or high frequency(5-20 kHz) descriptionof the shallowwater signaland noiseinput vectorsfor two networkarchitectures. Contour channel.The conditionsnecessary for the scatteringfunction descrip- plotsof the input-to-hiddenlayer weightsclearly indicate the relation- tion, namely that the channelbe wide-sensestationary with uncorre- ship betweenthe evolvingfeatures of the networkweights as they re- latedscatterers (WSSUS), are derivedand discussed.Specific examples spondto the inputsignatures during the learningprocess. Singular value of the scatteringfunction for differentchannels will be presentedand decompositionof theinput-to-hidden layer transfer matrix provides in- discussed.

THURSDAY MORNING, 7 OCTOBER 1993 SAVOY ROOM, 8:30 A.M.

Meeting of AccreditedStandards Committee S12 on Noise

to be held jointly with the

U.S. TechnicalAdvisory Group for ISO/TC 43/SC1 Noise and ISO/TC 94/SC12 Hearing Protection

D. L. Johnson, Chairman S12 EG&GSpecial Projects, Albuquerque Operations, Albuquerque, New Mexico 87119-9024

H. E. von Gierke,Chairman, U.S. TechnicalAdvisory Group (TAG) for ISO/TC 43/SC1, Noise 1325Meadow Lane, YellowSprings, Ohio 45387

ElliottH. Berger,Chairman, U.S. Technical Advisory Group (TAG) for ISO/TC94/SC12, Hearing Protection CabotSafety Corporation, 7911 Zionsville Road, Indianapolis, Indiana 46268-1657

StandardsCommittee S12 on Noise. Working group chairs will reporton their progress for the production of noisestandards. The interactionwith ISO/TC 43/SC1 and ISO/TC 94/SC12 activitieswill alsobe discussed,with referenceto the international standardsunder preparation. The Chairs of the respective U.S. Technical Advisory Groups (H E. yonGierke and E. H. Berger) willre•ort on current activities of theseInternational Technical Subcommittees under ISO and results of thelast meeting of ISO/TC 43/SC1,which took placein Oslo,Norway from 31 May-4 June1993.

Scopeof S12:Standards, specifications, andterminology in the field of acoustical noise pertaining tomethods ofmeasurement, evaluation,and control; including biological safety, tolerance and comfort, and physical acoustics asrelated to environmental and occupationalnoise.

1845 J. Acoust.Soc. Am., Vol. 94, No.3, Pt.2, Sept.1993 126thMeeting: Acoustical Society of America 1845 THURSDAY AFTERNOON, 7 OCTOBER 1993 GOLD ROOM, 1:20 TO 5:00 P.M.

Session4pAA

Architectural Acoustics: Room Acoustics and Sound Isolation

Edward R. MeCue, Chair Kirkegaard and Associates,954 Pearl Street,Boulder, Colorado80302

Chalr's Introduction---l:20

Invited Paper

1:25

4pAAI. Subjectiveand objectiveparameters of soundwithin fabric structures. Andrei N. Chesnokov (Lab. of Architectural Acoust., Res. Inst. of Bldg. Phys., Locomotivnypt. 21, Moscow 127238, Russia)

An investigationof acousticsin 15 circuseswith fabric roofshas beencarried out. Objectiveacoustical parameters (rever- beration time, clarity Cso, and others) have been measuredand questionnairesfrom the audiencein the circuseshave been obtained.Features of circusesacoustics are the decreasein reverberationtimes at low frequencies,echo (in hallswith impervious fabric roofs), and high levelsof backgroundnoise. The backgroundnoise levels in circusesbefore a performancewere equal LA=46-56 dBA.The questionnaire contained subjective acoustical attributes: Timbre, balance, reverberance, spaciousness, echo, loudness,clearness, audibility of backgroundnoise, background noise affect on speechlegibility, and others.Average mark estimatesand resultsof measurednoise level in halls (L^) have beensubjected to factor analysis.Three factorshave been extractedthat can be interpretedas (1) overallacoustical impression of the musicsound in a circus,(2) disturbinginfluence of the backgroundnoise, and (3) clarity of musicand speechsounding.

ContributedPapers

2:05 row Wilson,labor leaderSamuel Gompers, and very recentlyPresident Clinton, gracedthe podlure,a tradition that continuesto this day; and 4pAA2. A comparisonof three concert halls using impulse response the hall alsoaccommodates musical events and theatricalproductions. spectrograms.Mendel Kleiner, Patrik Falk, and Bj6ru Olsson (Dept. The Great Hall underwentreconstruction nearly 20 yearsago, but re- of Appl. Acoust.,Chalmers Univ. of Technol.,S-41296 Gothenburg, cent concernsabout its acousticalproperties led to the authors'mea- Sweden) surementsof the reverberationtimes in differentparts of the 900-seat Three concerthahs, Symphony Hall (Boston), ConcertHall at Otis auditorium.Reverberation times exceeding 3 s in the 125- to 1000-Hz A. SingletaryCenter for the Arts (Univ. Kentucky, Lexington), and rangepoint up the existenceof excessiveechoes that madespeech com- Konserthuset(Gothenburg, Sweden) have been investigated. The floor prehensiondifficult for many membersof the audience.Solutions are plansand sectionsof thesehalls are fundamentallydifferent as are the beingdeveloped to lower the reverberationtimes and to provideflexi- scatteringpropelhies of the walls and ceilingsof the halls. Impulse bility for meetingthe requirementsof differenttypes of events,with due responseswere recordedin a numberof positionsin each hall. These regardfor the landmarkstatus of the FoundationBuilding. impulseresponses were then analyzed using FFT and Waveletspectro- gramsto studyto whatextent the obviousgeometrical differences could 2:45 be tracedin the impulseresponses. The spatialdistribution of the sound in the hallswas studied using a "running"short-time interaural cross- 4pAA4. A nonlinear regression approach to the evaluation of correlationtechnique based on the impulseresponses recorded using a reverberationtimes using Sehroeder'sintegrated impulse response dummy-head.Results show that the waveletspectrogram yields graphs method. Ning Xiang (HEAD Acoust., Kaiserstr. 100, D-5120 which may be slightlyeasier to analyzethan conventionalFFT spec- Herzogcnrath 3, Germany), W. Ahncrt, and R. Feistel {ADA trograms.The expecteddifferences due to geometryare visiblein the Acoust.Design Ahncrt, Berlin, Germany) spectrograms.The short-timPintora_ura_l_ cross-,2orrelafien graphs add information which also agreeswith expectations. Reverberationdecay curves can be obtainedby backwardintegra- tion of room impulseresponses [M. R. Schroeder,1. Acoust. Soc. Am. 37, 409-412 (1965)]. The evaluationof reverberationtimes is often 2:25 achievedby a regressionline fitting the reverberationdecay eurve•. 4pAA3. The Great Hall at Cooper Union: A study of its acoustical However,the successfulapplication of this methodrequires either a problems. Daniel R. Raichel, Tanya Dragan, and Winston carefulchoice of theintegration limit or estimationof themean-square Wilkerson (Albert NetkenSchool of Eng.,The CooperUnion for the valueof backgroundnoise where background noise is presentin the Advancementof Scienceand Art, 51 Astor Place, New York, NY roomimpulse responses to be evaluated. In thepresent paper, an alter- 10O03) nativemethod for evaluatingreverberation times from Schroeder'sde- caycurves using a nonlineariterative regression approach is proposed. The Great Hall, a placefor publicassembly in the lower levelof the The regressionprocess is basedon a nonlinearcurve model using the FoundationBuilding at the CooperUnion in New York City, is steeped generalizedleast-square error principlerather than a linear modelas in history. Constructedin 1859, it was the site where Abraham Lincoln usedin the linearregression. The presentpaper will describethe prin- have his "Right Makes Might" speechthat catapultedhim to the Re- cipleof thisapproach and discussthe advantagesand disadvantages publicanpresidential nomination. Many prominentspeakers, including involved.Comparison of resultsobtained using this approach and alter- Mark Twain, feminist Victoria Woodhull, Theodore Roosevelt,Wood- nativemethods will alsobe presented.

1846 d. Acoust.Soc. Am., Vol. 94, No.3, Pt.2, Sept.1993 126thMeeting: Acoustical Society of America 1846 3:05 popularmusic toward strong bass content. Analysis of broadcastmusic signalsusing unbiased annoyance [E. Zwicker,"On thedependence of 4pAA5. Experiencingthe aural environmentof buildings. Gary W. unbiasedannoyance on loudness,"Proc. Internoise 89, pp. 809-814] Siebeinand Martin Gold (Dept. of Architecture,231 ARCH, Univ.of indicatesthat (i) contemporarymusic can be adequatelymodelled as Florida, Gainesville,FL 32611-2004) pinknoise from 50 to 4000Hz, (ii) afterpassing through a partitionthe A simpleaudio system was developed to allowarchitecture students 63-Hz octaveband dominatesloudness and unbiasedannoyance, (iii) to simulate the aural environment of various rooms. A basic set of existingsingle-number ratings (such as STC) cannotidentify structures exercisesprovide a conceptualand aural understandingof the room with criticallow-frequency resonances, thus potentially overestimating impulseresponse method for evaluatingsubjective acoustic qualities of performanceagainst this type of noise.Ramifications for noisecontrol rooms.The focusof the exercisesis to providea structurefor the practiceand effectivesingle-number ratings are explored. experientialunderstanding and manipulation of acousticsof buildingsin applied design situations. Aural demonstrationsillustrating how 4:20 changesin the impulseresponse such as the loudness,direction, and numberof earlyreflections as well as the subsequentreverberation affect 4pAAS. Time responseanalysis of sound fields in rooms and the the perceivedacoustical qualities of speechand musicare shownfor temperaturecondition of the air. Hidemoro Shimoda (Inst. of various environments.The exercisesare implementedusing anechoic Technol., Shimizu Corp., Etchujima 3-4-17 Koto-ku, Tokyo, 135 musicrecordings played via loudspeakersor headphones.The impulse Japan), Tatsuya Kashiwa, Norinobu Yoshida,and Ichiro Fukai responsesare simulatedusing digital delay and reverberator units. Once (Facultyof Eng., HokkaidoUniv., N-13 W-8 Kita-ku, Sapporo,060 theybecome familiar with the equipment,students can actually manip- Japan) ulatelistening conditions easily for an endlessopportunity of listening experiences. Transientanalysis in thetime domain is veryimportant to determine acousticalproperties in rooms.In this paper,the transmissionline net- workis usedas a simulationcode named Bergeroh's method [J. Acoust. 3:25-3:40 Break Soc.Am. Suppl.I 84, S64 (1988)]. Time responsesin the rectangular scalemodel excited with puretones were compared to analyticalresults. 3:40 In the study,the mediumcondition as a temperatureof the air turned out to be very sensitiveto simulatedtime responsesin soundfields in 4pAA6. Spectral properties of transmissionin a simulated room. rooms.Even though it is known that the soundspeed varies with a WilliamJ. Strongand Sining Li (Dept.of Phys.and Astron., Brigham changein the temperatureof the air, the standardsound speed corrc- Young Univ., Provo, UT 84602) spondingto thestandard temperature of theair, suchas 15øC in ordi- Transmissionof soundin a largeroom was simulated by meansof an nary soundfield simulations,is oftenused. Analytical time responses, imagemethod incorporating artificial diffusion. The simulationmodel however,as compared with experimentalrcsponses in the model, were wasvalidated by comparingthe standarddeviations of its transmission foundto be very differentfrom eachother in about 1% changeof the spectrato theoreticaland experimental results obtained by others.Sev- soundspeed. eral combinationsof sourceand receiverpositions were simulatedin order to assesstheir effectson spectralvariability. A singlesource and 4:40 singlereceiver arrangement resulted in the greatestvariability as ex- pected.Other combinations,including single-source/two-receiver (to 4pAA9. Necessaryaccuracy for early reflectionsin sound field representtwo ears),two-source (to representspatial extent of source)/ anralization. ToshiyukiOkano (TakcnakaRes. and Dcvelopmcot two-receiver,and five-source/five-receiver,were usedto assesstheir ef- Lab., 2-5-14 Minamisuna,Koto-Ku, Tokyo, 13fi Japan) fects.The effectsof frequencymodulation and criticalbands of the ear Necessaryaccuracy for early reflectionlevels was investigatedin were alsosimulated. In an attempt to relate simulationresults to sta- orderto derivecriteria to verifythe accuracyof a soundficld simulator. bilityin perception,a limit of 6-dBdifference in relativeharmonic levels between received tones and source tones was chosen as the criterion. On Early reflectionsare the mostimportant in controllingthe subjective impressionof a room'ssound field. The accuracyof the soundfield the basisof thiscriterion, a single-sourceand two-receiverarrangement simulatordepends primarily on the accuracyof earlyreflections. The incorporationcritical band effects and frequency modulation was found just-noticeablelevel difference(jnld) of early reflectionsdefines the adequateto providestable perception. maximum of allowable level difference between real and simulatcd re- fiections.Also, the maskedthreshold level (MTL) of early reflections 4:00 defines the level of the smallest reflections which a simulator should generate.However, jnld and MTL of carly reflectionsdepend on the 4pAA7. Music as noise:Sound transmission and unbiasedannoyance. soundficld's configuration. It is desirablethat criteriaare independent David A. Nelson (Acoust.Systems Acoust. Res. Facility, P.O. Box of the configurationof the soundfield. The jnld and MTL were mea- 3610, Austin, TX 78764) suredfor lateral and ceilingreflections in varioustypes of roomswith Musicis oftenperceived as noisepollution, especially when it in- simulatedsound fields. Measured jnlds and MTLs wcrcconverted into vadesone's solitudeor one'sown music making. This is generallya the differencein objectiveparameters (LE, IACCE, C80, etc.), which majorissue in multiunitresidential buildings and in musicfacilities for correspondto subjectiveimpressions caused by earlyreflections. Crite- rehearsal,broadcast, and recording.However, current noisecontrol ria for necessaryaccuracy were pursued in the domainof roomswith methodsof designand classification do not addressthe ongoingtrend in objectiveacoustic parameters.

1847 J. Acoust.Soc. Am., Vol. 94, No. 3, Pt. 2, Sept. 1993 126th Meeting:Acoustical Society of America 1847 THURSDAY AFTERNOON, 7 OCTOBER 1993 GRAND BALLROOM D/E, 12:55 TO 4:30 P.M.

Session4pAB

Animal Bioacoustics, Acoustical Oceanography, and Underwater Acoustics: Effects of Noise on Marine Mammals II

Charles I. Malme, Chair Bolt, Beranekand Newman, Inc., 70 FawcettStreet, Cambridge,Massachusetts 02138

Chairs Introduction--12:55

Invited Papers

1.•o

4pABI. Variability in behavioral reaction thresholds of bowhead whales to man-made underwater sounds. W. John Richardson (LGL Ltd., EnvironmentalResearch Associates, 22 FisherSt., P.O.B. 280, King City, ON LOG IK0, Canada) and CharlesR. Greene,Jr. (GreeneridgeSciences, Inc., Santa Barbara,CA 93110)

Reactionsof bowheadwhales, Balaena mysticetus, to actualand simulatedoil industryactivities were studied in the Beaufort Seaduring spring, summer, or autumnfrom 1980to 1991.Received levels of oil industrynoise that elicitedbehavioral reactions variedwidely, depending partly on the sourceand characteristicsof noise,the activityof whaleswhen exposed, and the physical situation(all levelsin dB re: 1 pPa, 20-1000-Hz band}. Reactionsto increasingnoise levels from approachingboats occurred at receivedlevels as low as 90 dB. In summer,roughly half the bowheadsshowed avoidance when the receivedlevel of steady drillshipor dredgenoise was about 115 or 20-dB aboveambient. Results in springwere similar, but somebowheads tolerated receivedlevels of drilling soundup to 135+ dB if the only availablemigration route throughice requiredclose approach to a soundprojector. In contrast,repetitive pulses from airgunarrays elicit•l avoidanceonly at receivedlevels exceeding 150-180 dB (although weakerpulses may elicit subtlebehavioral changes). Besides the variability amongsound types and situations,there is much whale-to-whalevariation in any one situation.No singlereceived level criterion is appropriateto all situations.[Work supportedby MineralsManagement Service.]

1:15

41•AB2.Resimnses of winteringhumpback whales to vesseltraffic. GordonB. Bauer (Div. of SocialSci., New College,Univ. of South Florida, 5400 North Tamiami Trail, Sarasota,FL 34243-2197), JosephR. MobIcy (Univ. of Hawaii West Oahu, Pearl City, HI 96782), and Louis M. Herman (Univ. of Hawaii, Honolulu, HI 96822}

Responsesof humpbackwhales to vesseltraffic were monitoredover two winter seasonsduring 1983-1984in Maui, Hawaii. A variety of vesselcharacteristics including vesselnumbers, speed, and proximity were associatedwith changesin whale behaviors,including swimming speed, , and socialbehaviors. Smaller pods and podswith a calf weremore affected than largerpods. A casestudy indicated that a calf couldbe sensitizedby the passbyof a largevessel, so that it subsequentlybreached in responseto noisefrom a smaller boat enginewhich had not previouslyelicited any behaviorchange. These findingsin conjunctionwith similar •sults from summeringhumpbacks in Alaska indicateddisturbance of humpbackwhales at both ends of their range.Although substantial short-term effects were noted,long-term negative consequences are not apparent.Recent aerial surveysof the HawaiianIslands indicate substantial increases in the numberof humpbackwhales.

1:•0

4pAB3. Responsesof humpback whales to playback of natural and artificial soundsin Hawaii. Adam S. Frankel and Louis M. Herman (Dept. of Oceanogr.and Psychol.,Univ. of Hawaii at Manoa, 1000 Pope Rd., Honolulu, HI 96822)

Humpbackwhales were exposed to the playbackof humpbacksong, social sounds, Alaskan feeding call, artificiallysynthe- sizedsounds, and blank tape controlwith a sourcelevel of 162dB re: 1/*PA. Whaleswere observedand trackedfrom shore.A 20-minbaseline observation preceded the 20-rainsound presentation. The J-11 transducerwas deployed at 7-m depthin water from 20 to 200-m deep.Acoustic velocity profiles conducted nearby indicated a uniformacoustic velocity field. The strongest reactionobserved was the rapid approachresponse wh•re whaleschanged course and approachedthe boat.The percentageof suchresponses varied with soundcondition. Rapid approachresponses were observedfrom whalesup to a 1.5-kindistance. Receivedlevels can be approximatedfrom the rangebetween transducer and whale. The minimumreceived level that produced a strongreaction was probablybetween 100-115 dB, for 20 and 15 log R transmissionloss models. These estimates could be improvedas someplayback experiments were recordedby a secondvessel.

4pAB4. Responsesof humpbackwhales to sonarsounds. Hilary L. Maybaum (OgdenEnvironmental, 680 lwilei Rd., Ste.660, Honolulu, HI 96817 and Dept. of Oceanogr.,University of Hawaii, 10(]0Pope Rd., Honolulu, HI 96822} Controlledsound playback experiments were usedto assesseffects of a low-frequencysonar system on humpbackwhales, Megapteranovaeangliae, in Hawaiian waters. Focal pods were presented with sounds of a 3.3-kHzsonar pulse, a sonarfrequency

1848 J. Acoust.Soc. Am., Vol. 94, No. 3, Pt. 2, Sept. 1993 126thMeeting: Acoustical Society of America 1848 sweepfrom 3.1 to 3.6 kHz, or a control (blank) tape. Behavior,movement, and underwatervocalizations were monitoredand comparedwith baselineperiods. While the two typesof sonarsignals differed in theireffects on thewhales, both elicited avoidance behaviors.Humpbacks responded to the pulseby increasingtheir distancefrom the soundsource. The strengthof this effect var/eddirectly with time.Responses to the frequencysweep primarily consisted of increasedswimming speeds and track linearity. The latter was a direct functionof increasingsound intensity. Overall, the soundsdid not stronglyor consistentlyaffect the whales'dive cyclesor vocalizations.Observed avoidance reactions may have resultedfrom possibleresemblance between the sonarsignals and naturalsounds in humpbacks'environment that are associatedwith biologicalthreats or warnings.

2:00

4pABS. Vocalizationsof blue and fin whales during a midoceanridge airgun experiment. Mark A. McDonald, John A. Hildebrand,Spahr Webb, LeRoy Doman (ScrippsInst. of Oceanogr.,Univ. of California, La Iolla, CA 92093-0205), and Christopher13. Fox (OSU Hatfield Marine Sci. Ctr., Newport, OR 97365-5258)

Numerousseismic experiments are conductedeach year in the deepoceans to studythe natureof oceaniccrust and to map the sourceof seismicsignals associated with smallearthquakes or volcanicactivity. Whale vocalizationsof the type associated with blue and fin whalesare often recordedon the arraysof seafloorseismometers and hydrophonesused for theseexperiments. Thesewhale vocalizations are characterizedfrom onesuch experiment conducted about 500-km offshore from Astoria,Oregon in Augustof 1990.The traveltime differences and signal amplitudes from bothdirect and multipath arrivals across the seafloor seismometerarray are usedto locatethe whalesand predictthe levelof shipand airgunnoise at the whale.Whale vocalizations wererecorded during airgun operations and these vocalization patterns are compared to patternsrecorded during times of relative quietfrom the 12 daysof data gatheredin thisexperiment. Transient oceanic sound levels from transformfault earthquakesand seafloorvolcanic activity are often louder than thoseproduced by airguns.

2:15

4pAB6. Underwater earthquakesnoise levels and its possibleeffect on marine mammais. Clyde E. Nishimura (Naval Res. Lab., Code 7420, Washington,DC 20375) and ChristopherW. Clark (Cornell Univ., Ithaca, NY 14850)

Earthquakesin oceanicregions commonly generate acoustic signals known as T-phases which arc similarbut not identical,to man-madeexplosions. As earthquake-producingareas are alsoregions where marine mammals congregate (e.g., Aleutiansand Caribbeanmargin), knowledge of the characteristicsof T-phasesmay provide some additional information on the possibleeffect of noiseon theseanimals. T-phases are generallycharacterized by acousticenergy below 100 Hz with mostof its energyin the 10- to 30-Hz range.The durationof the T-phaseis, to the firstorder, linearly related to the sourceearthquakes magnitude; durationsof severalminutes are common.The T-phasesource signal level, which can exceed200 dB re: 1/.•Pafor a magnitude 4-5 earthquake,is a complexfunction of the sourcemagnitude, focal depth, and the complexityof the bathymctryat tbe water-rockradiation area. This radiationarea is not a pointsource and can extendover a radiusof severaltens of kin. As part of the Whales'93 program,analysis has begun as to whetherthere is any correlationbetween the occurrenceof earthquakesand observablechanges in the acousticsignature form, and the positioningof large cetaceans.

2:30

4pAB7. The reaction of humpbackwhales to underwaterexplosions: Orientation, movements,and behavior. Jon Lien, Scan Todd, Peter Stevick, Fernanda Marques (Whale Res. 13roup,Memorial Univ., St. John's, NF AIB 3X9, Canada), and Darlene Kettcn (Harvard Med. School, Boston, MA 02114)

In 1992, local fishermenreported unusuallyhigh net collisionrates by humpbackwhales in Bull Arm, Trinity Bay, New- foundland(47 ø 45'N, 53ø 50'W), an areaof underwaterindustrial activity. As part of a studyto investigatethis phenomenon [see also Kcttcn eta]., this meeting],levels and typesof noise--includingunderwater explosions--were sampled. The locationand movementof a small groupof humpbacks(71 individualsidentified over a 19-dayperiod) residentin Bull Arm were monitored; when possible,behavior of individualswas recordeddirectly. CTD profilesand bait abundancewere alsonoted. Explosionswcrc of high amplitudeand low frequency.Measured at I mile from source,levels typically reached150 dB (re: I pPa at 1 m, at 350 Hz). Followingexplosions, residency time and locationof individualhumpbacks did not change.When individualscould be observeddirectly, no behavioralreaction to explosions(sudden dives, abrupt movements) were seen.Although not statistically significant,more animalswere sightedand resightingrates were higher in the explosionarea than in other parts of the bay. However,two animalsrecollided with fishinggear--such reports of successiveentrapments are rare.

2:45-3:00 Break

3:00

4pABS. Blast injury in humpbackwhale ears: Evidenceand implications. D.R. Ketten (Dept. of Otolaryngol., Harvard Med. School, MEEI, 243 Charles St., Boston, MA 02114), J. Lien, and S. Todd (Memorial Univ., St. John's, NF AIB 3X9, Canada)

To date, there is no publishedreport of effectson marine mammalhearing from underwaterexplosions. External injuries consistentwith inner ear damagehave been found in dolphinssubjected to ClassC explosives,but often little changeis seenin surfaceanimal behavior near blast areas [Richardson et al., OCS MMS/90-0093 ( 1991)]. In thisstudy, temporal bones from two humpbackwhales, which died followinga 5000-kgexplosion in Trinity Bay, Newfoundland[Lien et al., J. Acoust.Soc. Am. 94, 1849(A) ( 1993)], wereharvested, preserved in formalin,scanned with l-mm-highresolution spiral CT, decalcified,and sectioned at 20 p. Evidenceof mechanicaltrauma was found in all four ears:Round window rupture, ossicularchain disruption,sero- sanguinouseffusion of peribullarspaces, and dissectionof the middleear mucosawith pooledsera. In one animal, there were bilateralperiotic fractures. These observations are consistentwith blastinjury reportsin humans,particularly with damageto

1849 J. Acoust. Soc. Am., Vol. 94, No. 3, Pt. 2, Sept. 1993 126th Meeting: Acoustical Society of America 1849 victimsnear the source who sustained massive, precipitous increases in cerchrospinal fluid pressure. Them was no evidence that thepathologies found in thesewhales resulted from repeated orchronic infection, and no similar abnormalities were foundin controlears from humphacks not exposed to blasts.While the results show whales, like other mammals, are subject to severeblast trauma, it remainsunclear whether lower level stimuli induce temporary and/or acute threshold shifts in marine mammals.[Work supported by ONR Grant.No. N00014-92-J-4000.]

3:15 4pAB9.Prediction of potential disturbance of baleen whales by low-frequency acoustic transients. Charles I. Malme (25 RockwoodRd., Hingham,MA 02043) High-energy,low-frequency soundsources areuseful tools for geophysical surveying, detection, andlong distance acoustictomography. These sources produce impulsive, narrow-band andswept-tonal signals at highlevels in theoceanic environment.This study was made to estimatethe received level-time duration characteristics of acoustic transients that can potentiallyinfluence haleen whale behavior, thespecies ofparticular concern. Findings ofacoustic disturhance studies show that continuoussound levels )120 dB re:I pPaproduces )50% avoidanceby grayand bowhead whales. However, for impulsive airgunsounds ofduration •0.5 s,effective pulse levels 30 to 50 dB higher are required toproduce 50% avoidance forthe same species.Little information isavailable on whaleresponse to intermediate sound durations representative of some sonar and tomographysource operations. Consequently, theliterature onhuman response toacoustic transients wasexamined forresponse predictionmethodologies suitablefor application towhale acoustic response. Similarities werefound that support theapplication ofa modifiedequivalent level (L•q) metric. The exposure level-time duration characteristics obtained from this analysis are preliminaryestimates. Thepredictions should be tested using data obtained in the oceanic environment using representative sources,signals, and whales. [Work supported by the U.S. Navy.]

3:30 4pABI0.Recording, analysis, and verification of low-frequencysounds produced by Arcticoffshore drilling equipment. KennethD. Brewerand John D. Hall (Coastal& OffshorePacific Corp., P.O. Box31554, Walnut Creek, CA 94598) Digitalrecordings of underwater sounds produced byanchored and bottom-founded Arcticoffshore drilling equipment (drillingrigs) were made during drilling and idle conditions inopen water and under sea ice. Sound production wasverified by recordingthe frequencies produced byspecific pieces of equipmentaboard the rigs using a single axis accelcrometer. It was determinedthat most of thesound energy produced by boththe anchored and bottom-founded drilling equipment was in the frequencyband from I Hzto 1 kHz. The drill turntable and drive equipment onthe bottom-founded drilling rig produced sounds aslow as 1.8 Hz. The broadband [20Hz to 20 kHz source level (dB re: 1 pPa2@ 1 m] of the bottom-founded drilling rig ( 146.2 dB)was about 30 dB less than the broadband source level of the anchored drilling rig ( 178.6dB). Acoustic transmission lossin theinshore areas of the AlaskanBeaufort Sea, where water depths are less than 100 m, wasfound to be slightlygreater than cylindricalspreading ( -- 11.0 to -- 13.0log R dB)at the two sites about 350 km apart. [Work supported byARCO Alaska, Inc.l

3:48 4pABII.Variation in receivedlevel from man-made low-frequency underwater noise sources as a functionof divinganimal depth.William T. Ellison,Karen S. Weixel (Marine Acoust., Inc., 14 Pelham St., Newport, RI 02840),and Christopher W. Clark (Cornell Univ., Ithaca, NY 14850) Interestin the effectsof low-frequency( < 1 kHz man-madenoise on marinewildlife highlights the needfor accurate knowledgeofthe spatial distribution ofnoise levels within a givenwildlife habitat. These levels can vary significantly, particularly withrespect todepth within the water column. For diving animals, the ability to measure orpredict this variation with depth is a necessaryfactor in assessingthenet impact of that noise; i.e., one needs to perform a convolution ofdiving patterns (depth as a functionof time)with the noisepattern as a functionof timeand depth. Recent advances in rangedependent acoustic propagationmodeling allow for the ability to predict with some accuracy thetransmission lossfrom a knownsource ofnoise as a functionof sourcecharacteristics (directivity, sound spectrum, location, and depth) to anygiven location in a hypothetical habitat.Several examples are presented that illustrate how these models might be used to evaluatethe net impact of a passing noisesource on pelagicwhale species. [Work supported by ONR.]

4.-OO

4pABI2.Modeling noise interference with animal communication. Frank T. Awbrey (BiologyDept., San Diego State Univ., San Diego,CA 92182-0057) Regulatorsare proposing to set simplistic limits for anthropogenicnoise in naturalenvironments. These p•oposed limits specifyonly SPL, without regard to the method of measurement, frequency ortime weighting, normal ambient levels, or spectra. In somecases such limits may be inadequate, but in othersthey may be much too severe, resulting in unrealisticrestrictions on humanactivities, including scientific investigations, without real benefit to the animals. Realistic limitations onnoise level should incorporateinformation on thetime history and spectrum levels of thenoise and the animals' communication signals, with estimatesof hearingthreshold curves. This paper outlines an initial effort to devisesuch a modeland to estimatehow seriously noise of different kinds will limit communication.

4:15

4pABI3.Sonic boom wave propagation from air intowater: Implications for marinemammals. Victor W. Sparrow(Oraduate Prog.in Acoust.,Penn State Univ., 157Hammond Bldg., University Park, PA 16802}

1850 J. Acoust.Soc. Am., VoL 94, No. 3, Pt. 2, Sept. 1993 126th Meeting:Acoustical Society of America 1850 At the 1993NASA High SpeedResearch Program Sonic Boom Workshop, hosted by NASA AmesResearch Center, it ws notedthat the development of a highspeed civil transport in thenext several years will focusonly on overwatertravel. At that meetingit wasalso made clear that somehave raised concerns about the effectsof sonicbooms on the activitiesof marine mammals.Once a fleetof supersonicpassenger aircraft are in service,there could be hundreds of flightsper day, and, therefore, theeffects of sonicbooms on marinemammals should be well understood. The purpose of thepresent paper is to brieflydescribe the acousticpressure and intensity variations that onecan predict underwater due to a sonicboom impinging on an air-water interface.Arbitrary angles of incidenceare investigated, and the proportion of energyincident and reflected from the interface are givenfor typicalsonic boom wave forms.

THURSDAY AFTERNOON, 7 OCTOBER 1993 DENVER ROOM, 1:00 TO 4:45 P.M.

Session4pEA

EngineeringAcoustics and Structural Acousticsand Vibration: Vibration and Acoustic Monitoring of Machinery and Structures

Robert D. Finch, Cochair Departmentof MechanicalEngineering, University of Houston,Houston, Texas 77204-4792

Aynur Unal, Cochair 4255 SuzanneDrive, Palo Alto, California94306

Chair's Introduction--l:00

Invited Papers

1:05

4pEAl. Using soundand vibration to diagnosemachinery faults. Richard H. Lyon (MIT, Cambridge,MA and RH Corp., Cambridge,MA 02138) The relationbetween the dynamicalforces and structuralelements of a machineand the vibratoryor acousticalsignals producedas it operatesis far fromstraightforward. Nevertheless, a number of developmentsin measurement technology, system modeling,and signalprocessing have made it morepossible in the last few yearsto extractinformation about both mechanism performanceand structuralintegrity from vibrationor acousticalmeasurements. Measurement advances include smaller and more sensitivetransducers. System modeling advances include hybrid FEA and dynamic simulationmethods. And signal processingincludes a numberof methodsfor amplitudeand frequencydemodulation and deconvolutionprocedures. The paper will outlinea numberof theseadvances, illustrated by someof the author'sexperiences.

1:30

4pEA2.Acousto-ultrasonic nondestructive evaluation of materialsand structures. HenriqueReis (Dept. of GeneralEng., Univ. of Illinois, 117Transportation Bldg., 104S. Mathews,Urbana, IL 61801) A reviewof the natureand the underlyingrationale of the acousto-ultrasonicmethodology is presented.The term acousto- ultrasoniesdenotes a nondestructiveevaluation technique that combinessome aspects of acousticemission methodology with ultrasonicsimulation of stresswaves. Unlike most nondestructiveevaluation techniques, acousto-ultrasonics is lessconcerned with flaw detection than with the assessment of the collective effects of the various flaws and materials anomalies. Acousto- ultrasonicsis primarilyconcerned with materialproperties variations, such as the significantreduction in strengthand toughness causedby combinationsof minorflaws and diffuseflaws populations. Porosity content, and fatigueand impactdamage are typical examplesof factorsthat affect material properties variations. Applications of theacousto-ultrasonic approach to thenondestruc- tive evaluationof wire rope,porosity in laminatedcomposites, fatigue damage in ceramicmatrix composites, and adhesive bond strengthin fingerjoint connectionsof structurallumber and in otherstructural systems are presentedand discussed.

1:55

.4pEA3.Vibration and acoustic monitorin• of rotatinushafts. AndrewD. Dimarogonas(Deot. of Mech.Eng.. Washington Univ., Box 1185, St. Louis, MO 63130) Vibrationand acousticmonitoring of the operatingconditions and incipientfailures of rotatingshafts and other machine membershas been used extensively in the past30 years.The shaftvibration spectrum was used to obtaininformation about unbalance,bearing, and other instabilities in rotatingmachinery since the 1920's. It wasfurther identified in the 1960'sas a source

1851 J. Acoust.Soc. Am., Vol. 94, No. 3, Pt. 2, Sept. 1993 126th Meeting:Acoustical Society of America 1851 of informationfor the existenceof cracks,misaligned couplings, loose parts, and other unwanted operating conditions. Such conditionswou!d mainly introduce asymmetries of the rotating parts which would result in vibrationspectra in theacoustic range whichare characterized bythe response of parametrically excited systems, including sub- and superharmonics. Such signatures havebeen used for rotating machinery condition monitoring. It was further observed that field singularities, such as cracks, couple thelateral, longitudinal, and torsional vibration of rotatingshafts providing additional monitoring tools. Finall,, it wasfound that the nonlinearitiesassociated with closingcracks and gapsand journal misalignments lead to additionalinformation on the conditionof therotating parts, such as higher harmonics. In recentyears, the wealth of accumulatedobservation on the signatures of abnormaloperating conditions in rotatingmachinery have been incorporated in expertsystems for rotatingmachinery monitoring.Such systems have been developed using predicate logic or artificialneural networks. Further, fuzzy sets and interval analysishave been incorporated to accountfor nontraditionalrecording of operatingconditions.

Contributed Papers

2:20 A general physical model and method for tae calculation of the noisereduction provided by a tic ,t•leshield consisting of thin, rigid, 4pEA4. Decay of resonances of reinforced concrete beams with narrowplates, joined together le• !thwiseinto a chainis represented. cracks. Zhijing Wang, Shall Pandya,Robert D. Finch (Dept. of The modelselected is oneplane containing a setof linearrectangular Mech. Eng., Univ. of Houston, 4800 Calhoun Rd., Houston, TX platesplaced side-by-side, separated by narrow spaces.All platesare 77204-4792), and Ben H. Jansen (Univ. of Houston, Houston, TX makingflexural oscillation under the influenceof evenlydistributed 77204-4793 ) noisepressure. The model is basedon the determinationof the sound Reinforcedconcrete beams in practicaluse always contain cracks. pressurecaused by soundradiation of a thin rectangularrigid platein This paper reportsa study of the changesin decayrates of resonance averagefrequency range (63-8000 Hz), in far field.The lossfactor of frequencieswhen cracks occur in a vibratingconcrete beam. The exper- the platesjunction was determin:dexperimentally and usedfor the iments were performed using model reinforced concretebeams with calculationof the noisereduction. Some experimental data for the noise generalend conditionsas well as ideal pinned-pinnedend conditions. reductionprovided by differentdesigns (different number of the plates, The power spectrumand its time variationwere studied.The short time material, thickness)were representedand comparedto the calculated Fourier transform (STFT) techniquewas used. Theoretical studies results.The methodallows to determinethe optimalparameters which were made to establishthe effectsof damping on the vibration of the are necessaryto acl-ievemaxima of the noisereduction. [Work sup- beam.A complicationexists in that the reinforcedconcrete beam is in portedby Scientific-Research,h'•fitute of Printing Machinery,Mos- effecta compositematerial. The resultswill be comparedwith the data cow.] obtainedfrom a steelbeam of homogeneousmaterial [J. Robin, Acoust. Soc.Am. 92, 2441 (A) ( 1992)].The changedbehavior of decayrates of 3:15 resonancefrequencies could be a featurein the vibrationmonitoring of reinforcedconcrete structures such as highwaybridges. [Work sup- 4pEA7. Diagnosis of the Bjoerk-Shiley heart valve failure from portedby NSF Grant No. MSS-9024224.] acousticsign•tures. Thomas Chondros •Dept. of Mech.Eng., Univ. of Patras, Patra-:•Greece)

2:35 The replacementof human Leart valvesby m•chanicalones was 4pEAS. Responseof steel beams with elastically restrained end pioneeredin the 1960s.Shil :y, Inc., of Irvine, Califo• fia, wasone of the conditionswith and withoutcracks. ShailR. Pandya,Zhijing Wang, early manufacturersof suchvalves. The Bjoerk-Shiley60 convexo- Robert D. Finch (Dept. of Mech. Eng., Univ. of Houston,4800 concavevai ½e was introduced in 1967and about 85 000 people received CalhounRd., Houston,TX 77204-4792),and Ben H. Jansen (Univ. thisvalve until 1986, when it waswithdrawn from the market. Analysis of Houston,Houston, TX 77204-4793) of soundemitted from the stru•of the Bjoerk-Shiley600 CC valved ae to impactwas usedto monitorthe propagationof the fatiguecrack The vibrationresponse of uniformand crackedbeams with elasti- beforeit wouldlead to thefailure of oneor bothlegs of theoutlet strut. callyrestrained end conditions under impact excitation is beingexper- Analyticaland expecimentalresults established tha• the rangeof the imentallyinvestigated. Preliminary work hasre•,aled that the response fundamentalnatural frequencyis 2500 to 8000 Hz. It was found that obtaineddoes not matchthat predictedtheoretically for pinned-pinned previousexperimental investigations were performedwithin a window end conditions.In practice,most be;•:nsha• •.nol•classical end condi- of lowerfrequencies and they couldnot capturethe transitionof the tions as a certainamount of flexib•!ityis una,,,fidable.Therefore a the- natural frequencyduring the propagationof the fatiguecrack, which ory of vibration of beamswith elasxreally rest•,dned end conditionswas would take severalmt•ath•. ?. was foundthat for crack depthsabove applied.The resultsof this theor; were in cl.qseagreement with the 50% of the diameter,the • •,•.ngein the natural frequency,thus the responseobtained from beamsmounted on elas:icsupports. An antires- dominancomponent of th,. :ignal,was substantial and easilymeasur- onancefor the pinned-pinnedbeam ha.o been %und for the fifth modeof able.This may leadnot oni:. •o diagnosisof the:fracture at oneend of vibrationwhose frequency matches the natu.alfrequency of the s•p- the outletstrut but alsoto detectionof the propagatingcrack long ports.Cracks simulated by slotsare currentlybeing made at vari •us beforeit wouldlead to thepartial or completestrut failure. locationsalong the lengthof the Leam.The impactresponse of these slottedbeams will alsobe reporteeland comparisons will be madebe- tweenthe theoretical and the experimental results. [Work supported by - 3:3C NSF Grant No. MSS-9024224.] 4pEA8. Simultaneous n•c•.m•ment of structural vibration and temperatureusing an emb,..•ed.ptical fiber in a flat platecomposite 2:50-3:00 Break structure. DomainChiu , •d ¾lardiC. Hastings (Dept. of Mech. Eng., Ohio StateUniv., 206 Weot 18th Ave., Columbus,OH 43210)

3:00 Numericalresults from this studyshow that a singlepolarization- maintainingoptical fib,•r embedded in a compositefiat plateis ableto 4pEA6. Noise attenuationprovided by flexible shieldsfoL industrial simultaneouslymeasure low-frequency structural vibration and temper- equipment. Natalia V. Sizova (Cooperative Inst. for Res. iL ature.Thetactical estimates of sensitivitiesfor the opticalfiber sensor EnvironmentalSci., Campus Box 216, Univ. of Colorado,Boulder, CO are presentedwith considerationof the crosssensitivity caused by si- 80309-02 t 6 ) multaneousdisturbance.. An analysisof thecomposite plate and fiber

1852 d. Acoust.Soc. Am., Vol. 94, No.3, Pt.2, Sept.1993 126thMedting: Acoustical Society of America 1852 basedon the theoriesof linearelasticity and photoelasticityis usedto detectbearing flaws with the help of the adaptivenoise cancellation estimatesensitivities of the embeddedfiber. A finite element analysis algorithmwhen the microphonesare properlyplaced. usingANSYS is usedto determinethe stateof stressin the composite plate.Results of thisstudy show that simultaneous changes in structural 4:15 vibrationand temperaturecan easilybe resolved. 4pEAll. The three-dimensionallaser vibrometer. Joseph Vignola (SFA, Landover, MD 20785) and Brian H. Houston (Naval Res. 3:45 Lab., Washington,DC 20375-5000)

4pEA9. Acoustic diagnosisof the onset of strut fracture of the In the field of structuralacoustics, two of the central toolsnecessary BS/CC prosthetic heart valve. Allen C. Eberhardt and Charles E. for studyingthe physicsof interactionsand vibrationtransmission paths Chassaing (Structural Acoust., Inc., 5801 Lease Ln., Raleigh, NC are a measureof structuralintensity and the generationof k-o• disper- 27613) sion relationships.It is particularly important in the study of fluid- loadedstructures to be able to characterizeboth the in-plane and out- A replacementprosthetic heart valvefunctions in a corrosiveenvi- of-plane motions in order to identify mechanismconversions at ronmentin which it cannotreadily be inspectedor repaired.It must aperturesand discontinuities.A noncontactunderwater probe for mea- cycle repeatedly,at a rate of 40 million cyclesper year, over a service suringsimultaneously the three componentsof vibrationinduced dis- life that may extendmany years.The openingand closingsounds of placementon the surfaceof submergedstructures has been constructed. Bjoerk-Shiteyconvexo-coneave prosthetic heart valvesare brief tran- Opticalfiber is usedso that a compactoptical probe with no electronics sientsthat are beingstudied for detectionof incipientvalve failure. The is the only devicein the water. The probeis usedto measurethe three soundsare producedby the impactof the occluderdisk with the me- componentsof motionof a point on the surfaceof a target from a tallic strutsthat retainit within an orificering. Thesesounds have been distanceof approximately2 ft. Data for acousticstudies are obtainedby recorded in vivo for two distinct conditions or classes, valves that are collectingdata at a seriesof pointson a target surface.Experimental intact, and valvesthat exhibit an in-servicefailure of one of two legsof a strut which is critical to the function of the valve. The small size and resultswill be presented.An analysisof the sensitivity,frequency re- sponse,and detectionthreshold of the systemwill also be included. rapid motionof the valveoccluder disk producea broadbandacoustic transientthat exhibitssubtle changes as a valvestrut proceedstoward 4:30 failure. Featuresare detected,and a nonlinearexpansion is used to developa set of coefficientsfrom the time and frequencydomains to 4pEAl2. Sensitivity of axial vibration reactions to design separatethe two conditions.The recordedin uiuodata are usedas the asymmetriesin a Stirling cycle cryocoolerdual-opposed compressor trainingset. The coefficientsare then appliedto in vioorecordings as a assembly. Fred W. Hausle (Phys. AnalysisDept., Mail Stop WE-4, methodof detectionof a progressivefailure of the valve.Results of the Ball Aerosp.Syst. Group, P.O. Box 1062, Boulder, CO 80306) expansionand of a parallelapproach using neural netsare shownto be Stringentconstraints are placedupon allowablevibration reactions most effectivefor patientswith normal heart rhythm. from cryocoolersused for space-borneoptical sensors.Stirling cycle cryocoolerstypically use dual-opposed compressors to virtually cancel 4:00 the net axial reaction producedby the steady-statedriven oscillationsof 4pEAl0. Effect of microphoneplacement on adaptivenoise paired pistonsby virtue of symmetry.Under steady-stateoperation, harmonicsof the drive frequencyoccur due to the nonlinearcharacter- cancellation methods with machine ball bearing measurementsto detect bearing flaws in reverberant environments. Matthew S. isticsof both the workinggas and the mechanicalpiston support spring stiffnesses.Asymmetries in the systemdesign due to fabricationtoler- Carney and J. Adin Mann, III (Dept. of Aerosp.Eng. and Eng. Mech., Iowa State Univ., Ames, IA 50010) ancesmay result in intolerablenet reactionsprimarily at the harmonics of the drive frequency.The axial dynamicsof a simpletwo-degree-of- Soundmeasurements on operatingmachinery in reverberantenvi- freedomcompressor model are examinedusing a finite-differencetime- ronmentsare difficult to analyze.Adaptive noise algorithms [C. C. Tan, stepRunga-Kutta algorithm.The sensitivityof the axial reactionhar- IECON, 703-708 (1985)] are available to reduce the amount of back- monicsto asymmetriccharacteristics between the paired compressors ground noisein the measureddata. Due to the reverberationof the suchas gas volume,support spring stiffness and pistonmass is exam- environment,proper placementof the microphonesis important to ined.A Fourierdecomposition of the limit cycleis conductedto observe achievethe greatestnoise cancellationfrom the algorithm. Measure- the frequencycontent of the vibration reactions.Comparison is made mentswere taken on bearingswith known flaws underdifferent loads with resultsof an applicationof perturbationmethods. Cryocooler de- and speeds.Results of thesemeasurements will showthe effectivenessof sign parameterasymmetry tolerances based upon specifiedlimits on sound pressuremeasurements, and sound intensity measurements,to peak vibration reactionresponses are obtained.

1853 J. Acoust. Soc. Am., Vol. 94, No. 3, Pt. 2, Sept. 1993 126th Meeting: AcousticalSociety of America 1853 THURSDAY AFTERNOON, 7 OCTOBER 1993 GRAND BALLROOM A, 1:00 TO 4:55 P.M.

Session 4pED

Education in Acoustics:Teaching Laboratory Experiments

Uwe J. Hansen, Coohair PhysicsDepartment, Indiana State University,Terre Haute, Indiana 47809

Thomas D. Rossirig,Coohair PhysicsDepartment, Northern Illinois University,DeKalb, Illinois 60115

Invited Papers

1:00

4pEDI. Acousticslaboratory experiments for all levels. ThomasD. Rossing (Phys. Dept., Northern Illinois Univ., DeKalb, IL 60115)

Acousticsis a subjectthat is best learnedby incorporatinghands-on experience in the laboratory;this appliesto students majoringin musicas well as in physicsor engineering.The author'slaboratory manual, Acoustics Laboratory Experiments, describes52 experimentsat severallevels of sophistication.Some are intendedfor studentswith no previousexperience in a physicslaboratory, some for advancedundergraduates, and somefor graduatestudents beginning their studyof acoustics.Some experimentscan be performedon more than one level. Severalexperiments will be describedand demonstrated.

4pED2. Introductoryacoustics laboratory experiments. Uwe J. Hansen (Phys. Dept., Indiana State Univ., Terre Haute, IN 47809)

A courseon musicalacoustics designed for musicmajors with little or no backgroundin scienceserves a numberof purposes. Among theseis the intent to give insightinto the structureof musicalsound and the physicalnature of variousmusical instruments,and to enhancethe scientificliteracy of musicstudents. Meeting these objectives is enhancedsignificantly if students have the opportunityto learn with their handsand ears. A seriesof four introductoryexperiments will be describedand illustrated.These are ( 1) measuringfrequency with an oscilloscope,(2) complexwave synthesis with a simplekeyboard, (3) the spectrumof an elasticstring, (4) the inharmonicspectrum of a stiff string.

1:50

4pED3. Laboratory experimentsin the acousticscourse at the U. S. Naval Academy. S.A. Elder and M. S. Korman (Phys. Dept., U.S. Naval Aead., Annapolis,MD 21402)

For about25 yearsthe PhysicsDepartment has offeredan acousticscourse as a seniorelective for physicsand electrical engineeringmajors, based on the text by Kinsler,Frey, Coppens,and Sanders.A 2-h laboratoryis providedeach week. The aim of the lab is to illustratethe theoryby teachingbasic experimental measurement techniques. The specialtiesiuclude a modal analysissystem (B&K) to study,for example,the vibrationof guitars,Pyrex flasks, and student-made "musical" triangular steel plates.Students study the directivityof speakerarrays, musicalinstruments, and psychoacousticeffects in a 200-Hz-20-kHz anechoiechamber. IBM PC and Mac II work stationsprovide instruction in hardwareinterfacing, signal processing, spreadsheets (for data analysis),as well as specializedtechniques of FFTs and digital filtering.Work stationshave a midi-interfacefor sound and musicsynthesis. Ultrasantes and underwateracoustics experiments often involve electroacoustics. Projects include measuring the effectsof interference,diffraction, reverberation, and classification of materialproperties. In addition,each student participates in a majorproject, usually in a smallgroup. Recently the class performed an acousticalevaluation of thenew Bob Hope Theater of the PerformingArts on the USNA campus.

2:10

4pEIM. Undergraduateexperiments for duct acousticsand wind instruments.Peter L. Hoekje (Dept. of Phys.,Univ. of Northern Iowa, Cedar Falls, IA 50614-0150)

The acousticsof ductspresents a richspectrum of practicalstudent laboratory activities, from exposition of basicwave physics to explorationof importantcharacteristics of musicalwind instruments.A varietyof duct experimentswill bedescribed, extracted from a musicalacoustics course for music majors and a junior level vibrationscourse for physicsmajors at the University of Northern Iowa, as well as from an advancedacoustics seminar at Northern Illinois University.Basic physical phenomena exploredinclude resonance, wave speed, and wavelength.These can bc extendedto open-endcorrections, pressure, and velocity in a standingwave, acoustic impedance, and the dependenceof soundspeed on temperature,pressure, and gas composition. Wind instrumentfrequency responses can be easily observed. Small bore perturbations shift normal mode frequencies, demonstrating thatresonance frequencies arc affected by bore shape. Many of theexperiments described use an inexpensive impedance head built by studentsfrom a piezoelectricdriver and an electrctmicrophone. This device can be customizedfor specificapparatus, and stimulatesdiscussion of transducer design and use. Overall, students use simple apparatus to builda foundationof conceptual understandingwhich can be extended to fruitful research.

1854 J. Acoust.Soc. Am., Vol. 94, No. 3, Pt. 2, Sept.1993 126thMeeting: Acoustical Society of America 1854 2:30

4pEDS.A simpledemonstration of impedancematching in drivenresonant tubes. ThomasB. Gabrielson(NAWC Aircraft Div., Code5044, Warminster, PA 18974) and David L. Gardner (CDR, NOAA PacificMarine EnvironmentalLaboratory, Seattle, WA 98115)

Resonanttubes are oftenused in teachinglaboratory experiments to demonstratea widerange of topicsfrom standingwaves to lumped-parameterapproximations and electroacoustic analogues. The popularityis understandablegiven the ease of construc- tion and the broadapplicability outside the laboratory,ranging from impedancetubes to musicalinstruments. While the measurementof standingwaves and modes is common,the relationships,in an open-endedtube, between the tube,the radiation impedance,and the driver impedance is lessfrequently addressed. In thisexperiment using inexpensive components and a Smith chart, the resonancesof a small loudspeakerand of an opentube are measured.The radiationimpedance at the tube end is transformedto the driverlocation and the resultingreactance is comparedto the loudspeakerreactance. The tuberesonances are thus demonstratedto occurwhen the two reactancesare equal,but of oppositesign.

2:50

4pED6. The acousticalwaveguide. Alan B. Coppens,Anthony A. ArchIcy, and Eric W. Moore (Phys. Dept., Naval PostgraduateSchool, Monterey, CA 93943)

Fundamentalconcepts of normalmode propagation in boundedmedia can be studiedsimply and practicallyin a water-filled rectangularwaveguide with pressure-releaseboundaries. Use of broadbandsource and receiverallows generationand study of well-formedgated sine-wave pulses. The sourceis designedto excitethe lowest(I,I) normalmode of the systemand suppress excitationof the nextfew highermodes. This providesa usefulfrequency range for studyingthe behaviorof the lowestmode both aboveand below its cutoff frequency.The cutoff frequencycan be estimatedby a number of techniques;this relatescutoff to severaldifferent phenomena associated with the propagation.Tone burst operation allows study of the risetime of the propagating tone burstand therebythe groupspeed of the carrier frequency.With an appropriateabsorber at the far end of the waveguide, cw transmissionsare almostpurely travelingwaves so that the phasespeed of the input frequencycan be determined.The apparatusis simpleto constructand the electronicsare not exotic.This experimentis a direct descendantof one that originated in the graduatelab of the physicsdepartment at Brown Universityapproximately 35 yearsago.

ContributedPapers

3:10 environment,with modestcost and size. The sound speedinside one such deviceis approximately300 m/s, which allows 100-Hz measure- 4pED7. Linearizedleast-squares data analysis. S. L. Garrett (Phys. mentsin tubes 1 m long. The limitationsof the complianttube calibra- Dept.Sode PH/Gx, Naval PostgraduateSchool, Monterey, CA tor and examplesof measurementsmade usingthe calibratorwill be 93943) discussed. One of the mostattractive features of manyacoustic teaching labo- ratory experimentsis their ability to producehigh-quality (precision) 3:40 data. This affordsthe possibilityof alsousing the resultsof theselabo- ratory exercisesto teach advancedtechniques for data analysisthat 4pED9. Continuing developmentof the acoustics laboratory at the exploit the ubiquityof least-squaresdata analysisroutines which are CooperUnion. Daniel R. Raichel (Albert Nerken Schoolof Eng., now included in most hand-held calculatorsand all personalcomputer The Cooper Union for the Advancementof Sci. and Art, 51 Astor PI., plottingpackages. This talk will concentrateon the transformationof New York, NY 10003) generaltwo-parameter nonlinear equations into linearforms suitable for least-squares-fittingtechniques. This transformationtechnique will be As a result of the addition of new equipment,the scopeof the demonstratedto (i) extractthe effectivemoving mass of the springto acousticslaboratory curriculum at the CooperUnion is beingwidened correctthe simpleo=(k/m) •/2 expressionfor the simpleharmonic to include the use of FFT analyzers,reverberation meter, vibrating oscillator;(ii) extractthe distancefrom the end of the pendulumstring table,etc. Researchprojects are requiredof undergraduateseniors and to the pendulumbob center-of-massin the simplependulum experi- graduatestudents must meet thesis requirements. The laboratoryalso ment; (iii) extractthe locationof the acousticcenter of a projectorfrom servesas a researchcenter for thoseinterested in physicalacoustics, measurementof the free-fieldpressure versus separation; and (iv) ex- environmentalsciences, architectural acoustics, loudspeaker design, de- tract the cutoff frequencyand thermodynamicsound speed from the signof musicalinstruments, acoustics for medicaldiagnoses and treat- phasespeed versus frequency measurement in a water-filled,pressure- ment,and other acoustics-relatedtopics. Newly establishedliaisons be- releasedwaveguide. tween the Cooper Union ResearchFoundation and other institutions (Riverside ResearchInstitute, New York University Medical Center, U.S. Navy) open up additionalopportunities for thesiswork and pro- 3:25 vide accessto even more equipmentoutside the laboratory.Even fresh- men taking an integrateddesign course obtain acousticallaboratory 4pED8. A simple water-filled compliant-tubecalibrator. David L. experienceby workingin the anechoicand reverberationchambers in Gardner (CDR, NOAA Pacific Marine Environmental Lab., 7600 studyingsound effects around an abstractsculpture being planned for Sand Point Way, N.E., Seattle, WA 98115) and Thomas B. installationin New Mexico. [Work supportedby NSF and the New Gabrielson (NAWC Aircraft Div., Warminster, PA 18974) York StateScience and TechnologyFoundation.] Severalgeometries for low-frequencyunderwater calibrations are in commonuse, but often requireeither artecholewalls, rigid walls, or 3'55 tanks (or lakes) of large dimensionswith respectto a wavelength.Such facilitiesare frequently not practical for use in teaching laboratories 4pED10. A one-year acoustics laboratory course at UCSD. Duncan either becauseof inaccessibilityor becausethe facility must be shared McGehee, John A. Hildebrand, and Victor C. Anderson (Marine with active researchers.The compliant,water-filled cylindrical tube de- Phys. Lab., ScrippsInst. of Oceanogr.,Univ. of California, San Diego, scribedin this paperpermits low-frequency calibrations in a laboratory La Jolla, CA 92093-0205)

1855 J. Acoust.Soc. Am., Vol. 94, No. 3, Pt. 2, Sept. 1993 126th Meeting: AcousticalSociety of America 1855 The Universityof California,San Diego offers a one-yearacoustics WildflowerCt., Nederland,CO 80466) and Kimberly V. Fisher laboratorycourse to bothundergraduate and graduate students. The lab (Univ. of Oklahoma,Oklahoma City, OK 73190) is structuredto parallel a graduatelevel theoreticalacoustics class taughtjointly by the electricaland computerengineering department, The MultiSensorySound Lab electronically processes sound signals and the ScrippsInstitution of Oceanography.The acousticslaboratory from microphones,musical instruments/recordings, electronic stetho- courseexamines fundamental principles of acousticswith emphasison scopes,and other sources and directs them to loudspeakers,a vibrating oceanographicapplications. Also stressed are methods for handlingran- dom data and the professionalreporting of results.A GPIB buscom- floor,and various large visual technologies that display the frequency, puter is usedto controllaboratory instrumentation, and studentsde- spectral,intensity, and time aspects of thesignal. Originally developed velopapplication programs for eachexperiment. The courseis divided for usewith deafchildren, the lab providesvisual and tactile informa- into 17 separateexperiments. The first quarteris devotedto the mea- tionabout sound that is usefulin a widerange of applicationsranging surementof mechanicalimpedance and resonance in a spring-masssys- frominstruction in acousticsand physics of sound,to speechand music tem, velocityand dispersionin stringsand bars,and normal modesin a therapyfor normallyhearing, as well as, hearing-impairedstudents. bar. The secondquarter examinesthe calibrationof transducers,includ- Exampleclinical and educationalapplications will be presented.Data ing self-reciprocityand beam-patternmeasurements, reflection and from pre- and post-testingshow that soundlab activitiesresult in sig- transmissionin multiple media, sound-speeddependence on salinity, nificantconcept learning and skill acquisition.User surveysshows that and normalmodes in a channel.The third quarteremphasizes the treat- the soundlab easesteaching tasks and motivatesstudents. Note: this ment of randomdata including:Power measurementsof band-limited presentationwill serveas introductionto the MultiSensorySound Lab whitenoise, scattering of soundfrom surfaces of varyingroughness, and toursthat will be conductedat the Universityof Colorado.[Project detectionthreshold experiments. supportedby the U.S. Departmentof Education.]

4:10

4pEDll. Laboratoryexperiments on the interactionof an air jet with 4:40 a Helmholtz resonator. James P. Cottingham (Phys. Dept., Coe 4pEDI3. Vibration analysisof an alpine ski. Richard Chapman, College,Cedar Rapids,IA 52402) Karl-ArneHegewald, Steve Humphreys, and Scott Meekstroth (Dept. The interactionof an air jet with a resonatoris fundamentalto the of Mech. Eng., Univ. of Colorado,Boulder, CO 80309) operationof severalmusical instruments and a significanttopic in mu- sical acoustics courses. Recent studies of a Hclmholtz resonator excited An investigationinto the vibrationalbehavior of an alpineski ex- by an air jet haveexplored the dependenceof the frequencyand ampli- citedby a single-pointforce applied at the tip of the ski wasconducted. tude of the Helmholtz mode on jet speedand other parameters.JR. Thesingle-point force was used to modelsmall amplitude perturbations Khosropourand P. Millet, J. Acoust.Soc. Am. 88, 1211-1221( 1990); in the snowfor a flat runningski to investigateski chatter.In this J.P. Cottinghamet al., J. Acoust.Soc. Am. 92, 2380 (1992)]. It has respect,the bindingswere assumedto remainin constantcontact with beenobserved that domainsof jet speed,for which a single-frequency the snowsurface and the testski wasclamped at theselocations for the Hclmholtz mode occurs,arc separatedby narrow transitionregions. experiment.An accelerometerand a personalcomputer were usedto Investigationof this phenomenon,which is audibleas well as measur- able, hasbeen adapted as a set of laboratoryexercises for usein musical measurethe ski's responseto tip excitationand a FI:rT was usedto determine the ski's harmonics. Numerical models were constructed uti- acousticscourses. Using a homemadeair jet with the laboratorycom- pressedair supply,students arc able to study the internal soundfield of lizing (i) a finite elementapproximation, and (ii) a finite difference a jet-excitedresonator with a smalltie clip microphone.Investigation of solution,to determinefrequencies at 21 distinctpoints of the ski. Re- a significantnonlinear phenomenon is thuspossible with simpleequip- sultsfrom the modelwere then compared with experimentaldata and ment. the model was validated.Experimental results showed the first three harmonicsfor the front of the ski to be 2 4-0.5 Hz, 22 + I Hz, and 434-4

4:25 Hz. Thiscompared with theoreticalvalues of 5, 25, and37 Hz. Exper- imentalresults for thehigher harmonics and other parts of theski were 4pED12. MultiSensorySound Lab for Educationaland therapeutic foundto bewithin an orderof magnitudeof thetheoretically predicted applications. Norman Lederman (Oval Window Audio, 33 values.

1856 J. Acoust.Soc. Am., Vol. 94, No. 3, Pt.2, Sept.1993 126thMeeting: Acoustical Society of America 1856 THURSDAY AFTERNOON, 7 OCTOBER 1993 SILVER ROOM, 1:30 TO 5:30 P.M.

Session4pPA

Physical Acoustics:Physical Acousticsfor Materials Characterization II

Dale E. Chimenti, Chair Departmentof AerospaceEngineering and EngineeringMechanics, Iowa State University,•Imes, Iowa 50011

Invited Papers

1:30

4pPAI. What physicalacoustics can tell us aboutfluids. RobertT. Beyer ( Dept. of Phys.,Brown Univ., Providence,RI 02912)

Traditionally, one has usedphysical data on fluids to study the propagationof soundin them. However, the oppositeis also possible:To usethe studyof the propagationof soundin a fluidto determinesome of its physicalproperties and its behavior.This was perhapsdone for the first time by Einstein(for propagationin gases)in 1920.Today, physicalacoustics can be usedto gain informationabout phase transitions in liquid crystals,to studythe behaviorof mixturesof liquids,and of particlesor bubblesin liquids,and in other ways. A reviewis givenof theseprocesses and the ways in which physicalacoustics contributes to our knowledgeof them.

2:00

4pPA2. Thermophysical properties of alternative refrigerants from acoustical measurements. Michael R. Moldover (Thermophys.Div., Natl. Inst. of Standardsand Technol.,Gaithersburg, MD 20899)

Acousticresonance techniques have beendeveloped at NIST to make accurate( •-0.01% ) speed-of-soundmeasurements in gasesa routinematter. Thesetechniques have been applied to many environmentallyacceptable candidate replacement refrig- crants.The data wcrc usedto deduceideal-gas heat capacitiesand virial coefficients.These results arc an importantcomponent of tbe computerpackage REFPROP that is beingused by designersof refrigerationequipment. NIST is activelyinvolved in developingacoustic methods for determiningthe viscosityand thermal conductivityof gases.NIST is also extendingthese measurementtechniques to corrosivegases and to gasesat high temperatures.

2:30

4pPA3. Ultrasonic dispersionresulting from inelasticgaseous collisions and someinferences regarding molecular interactions and force laws. Robert C. Amme (Dept. of Phys., Univ. of Denver, Denver, CO 80208)

Ultrasonicshas been, and remains,a valuabletechnique for the investigationof vibrationalenergy transfer in polyatomic gases.The celebratedtheory of Schwartz,Slawsky, and Herzfeld (SSH) hasproven to be greatlysuccessful in predictingthe efficiencyof V-T processes,particularly for self-collisionsof diatomicspecies or betweenthese species and the noblegases. For morecomplex molecules, particularly those containing hydrogen atoms, the role of vibrationalamplitudes and of rotational(R-T and V-R,T) energytransfer effects may complicatethe picture.Moreover, the presenceof multiplerelaxation processes may causefurther departure from singlerelaxation steps in the soundvelocity measurements. Nevertheless, the basic approach of SSH theoryremains qualitatively correct in manycases, once the proper relaxation process and the interaction potential are identified. Vibrationalcollisions numbers Zm, in polyatomicmolecules, i.e., the averagenumber of collisionsrequired for the vibrational transitionv = 1• v= 0, will be discussedboth for room temperatureultrasonic measurements and, for somespecies, over a range of temperatures.Various predictive schemes will be reviewed,and somerecent results on substitutedethanes and their mixtures will bepresented. It will be shownthat the SSHformulation gives agreement with theseexperiments when a verysteep repulsive potentialis employed.

3:00-3:15 Break

ContributedPapers

3:15 and the substrate-sideinsonification. A systematicanalysis of the sen- sitivityof the transferfunctions to the thicknessand wavespeedhas been 4pPA4. Ultrasonicnondestructive evaluation of thin (subwavelength} carriedout. An inversealgorithm has been developed to reconstructthe coatings. C. Zhu and V. K. Kinra (Ctr. for Mech. of Composites, thicknessand the phasevelocity through a comparisonof the theoretical Dept. of Aerosp. Eng., Texas A&M Univ., College Station, TX and the measuredtransfer functions.Using this techniqueboth the 77843-3141 ) thicknessand the wavespeed of the coatingcan be extractedfrom the same measurement,without knowing either. The technique was used to This paperdescribes a techniquefor ultrasonicnondestructive eval- measurethe thicknessand wave speedof epoxy and Plexiglascoatings uation of a thin coating (subwavelength)on a thick substrate.A plane (50-100 pro) on an aluminumsubstrate using low-frequency (10 and longitudinalwave which is normallyincident upon the coatingis con- 20MHz) transducers; theratio of thickness/wavelength wasabout «. sidered.Transfer functions have been derived for both the coating-side The precisionin the measurementof the thicknessand the wavespeed

1857 J. Acoust.Soc. Am., Vol. 94, No. 3, Pt. 2, Sept. 1993 126th Meeting:Acoustical Society of America 1857 wasfound to be 4-2/•m and 4-3%, respectively.[Work supportedby of two volumes,one of whichis drivenby a loudspeaker at frequencies Texas AdvancedTechnology Program.] low enough so that the two volumes can be accurately modeled as lumpedelements. It is shownthat Z and B primarily dependupon on the pressuretransfer function between the two volumes,which can be 3:30 measuredvery quicklyand accuratelywith modernanalyzers. Due to 4pPAS.Attenuated leaky Rayleighwaves, QuanQi (Dept. of Theor. the simplicityof the apparatus,it is felt that th/s techniqueis superiorto and Appl. Mech., Univ. of Illinois, Urbana, IL 61801) methodspreviously used [J. D. Mcintoshet aL, J. Acoust.Soc. Am. 88, 1929-1938 (1990)], howeverit is limited to lower frequencies( <500 The attenuationof leaky Rayleighwaves due to viscousdamping in Hz with the current apparatus). Measured impedancedata of mem- a boundarylayer at the interfaceof an elasticsolid half-space and a fluid branes,plates, ports, perforated plates, and porousmaterial is presented half-spaceis studiedby matchedasymptotic method. Viscosity of the as well as bulk propertiesof opencell foam. fluid is consideredunimportant except in a thin boundarylayer at the interface.By keepingthe leadingorder effect, shown by the inverseof squareroot of a Reynoldsnumber based on the shearvelocity of the solid substrate,a new characteristicequation is obtained.One of the 4pPA9. Characterizing scatterer size via measurementsof multiple numericallyobtained solutions gives the leakyRayleigh wave speed and acousticparameters. Peng Jiang and Robert E. Apfel (Dept. of the attenuation coefficient due to both radiation into fluid and viscous Mech. Eng., Yale Univ., New Haven, CT 06520) dampingof theboundary layer. It is shownthat the viscousattenuation in the boundarylayer may be asimportam as that dueto radiationinto A multipleparameter approach for characterizingmixtures has been thefluid half-space for somefluid--substrate combinations. These results investigated.It is foundthat onecan characterizescatterers (droplets} may be usedto improveour interpretationof experimentalresults of in immisciblemixtures of water,fat (oil}, and protein,in term of vol- acousticsignature of materials.Extension of the analysisto a fluid layer ume fraction and size, from measurements of the mixture's effective insteadof a half-spacewill be discussed.[Work supportedby the Hunt acousticparameters (density, sound speed, the acousticnonlinear pa- Fellowship.] rameter,and attenuation).Mixture laws [P. Jiang et aL, Ultrasound Med. Biol. 17(8), 829-838 (1991)] wereused to determinethe compo- sition of a mixture. A procedurefor choosinga reliablecomposition 3.'45 predictorwas proposed.Good agreementbetween the predictedcom- 4pPA6. Reduction of backscatter coefficient from pulse-echo positionsand the known valueshas beendemonstrated. After the vol- measurements:A new formulation. Xucai Chen, Jack G. Mottley, ume fractionof the scatteringdroplet was found, an effectiveradius of Karl Q. Schwarz,and Kevin J. Parker (RochesterCtr. for Biotaed. the dropletswas obtained by usingan appropriateattenuation law with Ultrasound, Univ. of Rochester,Rochester, NY 14627} the measuredfrequency-dependent attenuation. The deducedradius is closeto that of the majority of dropletsobserved under an optical A new formulation for the reduction of the absolute backscatter microscope.A discussionis givenon how to apply the techniqueto coefficientfrom pulse-echomeasurements is presented.Using this for- characterizethe sizedistribution of scatterers.[Work supportedby Nit{ mulation,the diffractioncorrection is straightforward.This correction throughgrant R01-GM30419.] is a weak function of frequency,rather than the frequencysquared dependenceproposed by earlierinvestigators. A much simplercalibra- tion methodis prolxxsed.Initial experimentalevidence using a focused 4,'45 transducerand polystyrenespheres as scattersis presented.The pro- posedformulation and polystyrenespheres are sufficientlysimple as to 4pPA10. Acoustic characterization of chemically altered cortical be utilized in many laboratories,enabling cross checking and consis- bone. Jerry J. Broz (Dept. of Mech. Eng. and The Ctr. for Acoust. tencybetween sites. [Work supportedby NIH and NSF.] Mech. and Mater., Univ. of Colorado, Boulder, CO 803O9), Steven J. Simske,and Alan R. Greenberg (Univ. of Colorado,Boulder, CO 803O9) 4:00 A novelcombination of microscopicevaluation techniques is uti- 4pPA7. Acousticcoupling from a focusedtransducer to a flat plate lized to evaluatelocalized compositional and materialproperties of bo- and back to the transducer. Xucai Cben, Karl Q. Schwarz, and vine fernoralcortical bone.Cortical bonesections were selectivelydem- Kevin J. Parker (Rochester Ctr. for Blamed. Ultrasound, Univ. of ineralized by timed immersion in supersaturated(ethylenedinitrilo)- Rochester, Rochester, NY 14627) tetraaceticacid. Optical microscopyof the sectionsindicated that a collagenlayer of varying thicknesssurrounded a core of mineralized An exact solutionfor the acousticcoupling function from a focused tissue.The treatedsections were characterized with a scanningacoustic transducerto a fiat plate and back to the transducer(the diffraction microscope(SAM) usinga 50-MHz transducer.Based on the acoustic correctionfunction) is provided.This functionis usefulfor the system signalsreflected from both the surfaceof the collagenlayer and the calibrationwhere is pulse-echosystem or transmit-receivesystem is mineralizedtissue layer below, the sonic wave velocitiesand elastic used.Numerical resultswill be presentedfor the casewhere the refer- stiffnessesof the mineralizedtissue and collagenwere 3.654-0.12 km/s enceplate is placednear the focalplane of the transducer.The solution and 1.494-0.06km/s and 27.24-2.5 GPa and 2.954-0.26GPa, respec- for a fiat disktransducer is obtainedas a limitingcase. [Work supported tively [Broz et al., 12th South.Biomed. Conf., Tulane Univ. (1993)]. by NIH and NSF.] Following the acousticevaluation, microhardness and elementalcom- positionmaps were obtained for the sectionsusing a diamondpyramid 4:15 indenter and a Jeo] JXA-8600 Superprobe,respectively. The size and locationof the demineralizedregions as determinedby the microhard- 4pPAS. A simple apparatus for measurement of the acoustical nesstesting and wave dispersiveanalysis were in goodagreement with impedance of membranes,plates, and the bulk properties of porous the acousticmicrograph data. The combinationof acoustic,chemical, materials. JasonMcintosh (Digisonix,Inc., 908 StewartSt., Madison andmechanical microscopic techniques provides important insights into WI 53713} the site-specificphasic properties of corticalbone. An apparatushas been built that can measurethe acousticalimped-

ance(Z) of a varietyof acousticalobjects including membranes, plates, 5.-O0 and porousmaterials. It is alsopossible to usethe techniqueto measure the complexbulk modulus(B) of air within a porousmaterial. When B 4pPA!I. Design of ultrasonic scattering experiments for tissue is combinedwith Z, a completelinear descriptionof the bulk properties characterization. T. DouglasMast and Robert C. Waag (Dept. of of porousmaterial is obtained.The apparatusis very simple,consisting Elec. Eng., Univ. of Rochester,Rochester, NY 14627)

1858 J. Acoust.Soc. Am., Vol. 94, No. 3, Pt. 2, Sept. 1993 126th Meeting:Acoustical Society of Amedca 1858 Measurementsof differentialscattering cross section as a functionof Ultrasonicnondiffracting beams are of interestfor usein pulse-echo angleand frequencymake possiblethe separationof compressibility systemsbecause they have long depth of fieldand small beamwidth. effectsfrom densityeffects. From thesemeasurements, one can obtain Recently,a newclass of nondiffractingbeams, termed the x waves,has thepower spectrum of compressibilityvariations, the power spectrum of beendiscovered and its propertiesin losslessmedia have been reported. densityvariations, and the crossspectrum of compressibilityand den- In somepulse-echo applications, however, propagation media are dissi- sity variations.Measurements of thesespectra has potentialuse for patlye.It can be shownthat x wavesdiffract in suchmedia, i.e., the tissuecharacterization on scalescorresponding to the wavelengthsem- beamspreads and its amplitudedecays with distance.In orderto limit ployed.Here, conceptsare presentedthat makepossible optimal design of experimentsto measureultrasonic scattering as a functionof angle beamspread within a reasonablerange, attenuation of the mediamust and frequency.Conditions are givenfor emitterand detector beam pat- be takeninto accountwhile designing the transducerand the excitation ternsand time gatesthat yield measurementsystem-independent scat- signal.Also, amplitude decay of theechoes must be compensatedfor at teringdata. A methodis presentedfor minimizationof the effectsof the receiverby usinga propertime gain compensationcurve. In this statisticalfluctuations in the scatteringestimates by solutionof an over- paper,conditions for designingan x wavepulse-echo system for usein determinedset of equations.The limitationsof suchmeasurements are dissipativemedia are described.Given the attenuationcoefficient and alsotreated. As an example,an experimentcurrently being designed is maximumallowable beamwidth, proper values for transducerparame- discussed;the goalof thisexperiment is to measuredifferential scatter- ters,such as diameter,axicon angle, beam concentration parameter in ing crosssection with greaterspatial resolution than hasbeen achieved losslessmedia, and the bandwidthof the interrogatingpulse are dis- to date. cussedand determined. Also, variations of the beamwidth are investi- gated.It is shownthat for widebandx waves,the beamspreads linearly 5:15 with depth.Furthermore, analytical expressions for the time gaincom- 4pPAI2. Limitationsintroduced by material attenuationin pulse-echo pensationcurve are obtained. In contrastto the conventionalexponen- systemsemploying nondiffracting x waves. Mostafa Fatemi (Elec. tialgain function, the gain function for thewideband x wave approaches Eng. Dept., AmirkabirUniv., Hafez St., Tehran,Iran) a linear function of time.

THURSDAY AFTERNOON, 7 OCTOBER 1993 VAIL ROOM, 1:25 TO 3.45 P.M.

Session4pPP

Psychologicaland PhysiologicalAcoustics and Musical Acoustics:Temporal and Pitch Processing,Singing, and the

Diana Deutsch, Chair Departmentof Psychology,University of Californiaat San Diego,La Jolla, California92093

Chair's lntroduction--l:25

ContributedPapers

1:30 The jnd for a perturbationof the timing of a tone appearingin a metricalsequence was examined in an experiment,where 30 listenersof 4pPPI. Relation invarianceof expressivemicrostructure in music variedmusical background were asked to adjustthe timing of thefourth performanceacross moderatechanges in tempo. Bruno H. Rcpp tonein a sequenceof six,such that they heard the sequenceas perfectly (Haskins Labs., 270 Crown St., New Haven, CT 06511-6695) regular.The toneswere presented at a constantinteronset time that was Two pianistsplayed Shumann's "Tr•iumerei" three times con espres- variedbetween 100 and 1000ms. The averagejnd wasfound to be about sioneat eachof threemusically acceptable tempi, and the performances 10 ms for tones shorter than about 240-ms duration and about 5% of wererecorded in MIDI format.A perceptualtest showed that artificial the durationfor longertones. Subjects' musical training did not appear modificationof the tcmpi of theseperformances within the samemod- to affect these values. eraterange does not lead to a noticeabledeterioration of performance quality.Subsequent analyses confirmed that the expressivetiming pat- 2:00 terns very nearly maintainedrelational invarianccacross tempo changes.Other temporal details, however, did notexpand or contractin 4pPP3. A psychologicalexperiment on quantitativejudgment for this fashionbut were unaffectedby tempo;they includedchord asyn- transpositionof melodies. Tamotsu Shitado and Masuzo Yanagida chronics,tone overlaps, and possiblypedal timing. This indicatesdis- (Kansai Advanced Res. Ctr., Commun. Res. Lab., 588-2, lwaoka, tinct levelsof cognitiveand technicalcontrol in musicperformance. Nisi-ku, Kobe, 651-24 Japan) Dynamicpatterns were essentially unaffected by tempochanges, though Novice musicianshave difficultyin judgingthe interval betweena a slightincrease in overalldynamic level with tempowas noted. The melodyand its transposequantitatively. It is expectedthat the moreone generalityof thesefindings needs to betested with other types of music. accumulatesmusical experiences, the morehe or shecan improvetheir

1:45 abilityof quantitativejudgment for the intervalbetween a melodyand its transpose.It is supposedthat this ability dependson abilitiesof 4pPP2. Perception of just-noticeable time displacement of a tone absolutepitch. Psychologicalexperiments wcrc conductedto invcstigatc presentedin a metricalsequence at differenttempos. AndersFriberg relationsamong theseabilities. Single tones, pairs of singletones, and (Dept.of SpeechCommun. and Music Acoust., Royal Inst. of Technol., pairs of melodiesand their transposesgenerated by a synthesizerwcrc Box 70014, S-100 44 Stockholm, Sweden) and Johan Sundberg usedfor the experiments.Subjects (students majoring in music) were (Royal Inst. of Technol.,Stockholm, Sweden) askedto givepitch names of singletones presented in isolation,to judge

1859 d. Acoust.Soc. Am., Vol. 94, No. 3, Pt. 2, Sept. 1993 126th Meeting:Acoustical Society of America 1859 intervalsbetween two singletones presented sequentially, and to esti- for the PerformingArts, 1245 ChampaSt., Denver, CO 80204) mate the interval betweena melodyand its transposepresented on a continuousrhythm pattern. From the experiments,it can be seenthat Four singers(soprano, alto, tenor, and bass) simultaneouslyre- corded unison /a/ vowels on middle-C (261 Hz) in seven different there are varioustypes of difficultiesin judging musicalintervals be- tweentwo singletones and thosebetween melodies and their transposes. conditions:No instruction,matching or aggregatingvibratos, matching Further, weak correlationhas beenfound betweenthe ability to judge or aggregatinga nonvibratotone quality, matching vowel qualities with intervalsbetween two singletones, and the ability to judge intervals and without vibrato,and prescribedinstructions for a "target" vowel betweena melody and its transpose. with and without vibrato.A perceptualpanel of choraldirectors, sing- ers, and naiveauditors rated the blendor homogeneousquality of ran- domizedsamples of the unisonvowels. Spectral analyses of the unison 2:15 /a/samples indicatedvarying deviations of the actualfrequency of the 4pPP4. The interaction of pitch, harmonics,and the equal loudness first 14 partials (0-4000 Hz) from the calculatedinteger multiples of curvesin timbre analysisof musicaltones. JamesM. Pyne (Schoolof the fundamentalfrequency. The tabulatedresults of the auditorswere Music and Ctr. for CognitiveSci., Ohio StateUniv., 1855 CollegeRd., correlatedwith the percentageerror betweenactual and calculated par- Columbus, OH 43235) tial frequencies.[Work supportedby NIH Grant No. R08 DC01150- 03.] Highly skilledmusicians encounter great difficulty when attempting to communicateinformation concerning the timbre of musicaltones. 3:15 This canbe a barrierto effectiveteaching in that musicianstend to think of individualsounds as unifiedsingle events rather than complexcom- 4pPP7. The tritone paradox and speakers' voice range: A dubious poundsthat establishtimbre characterizations.When taken into the connection. Bruno H. Repp (Haskins Labs., 270 Crown St., New realm of visual representation,understanding can be more easily Haven, CT 06511-6695) achieved.The utilization of a SpectralDynamics real-time analyzerhas Dcutschand her co-workers[Music Percept.7, 371-384 ( 1990); 8, allowedcoached student performera to react to a spectraldisplay and 335-347 (1991)] have proposedthat individualdifferences in the per- has provenuseful in tone quality development.Of specialconcern has ceptionof the so-calledtritone paradox(i.e., the perceiveddirection of been the reductionof excessiveharshness when producingloud tones, pitch changein pairsof Shepardtones six semitonesapart) derivefrom and clarity when producingsoft tones,both commonproblems in per- listeners'reference to a templateacquired through experience with the formance.Further definitionconcerning the interactionof pitch, har- pitch rangeof their own voice.Dcutsch has reporteda strikingdiffer- moniccontent, and the equalloudness curves has been useful in a better encein tritone perceptionbetween American and British listeners,as mutualunderstanding of this processand it may alsobe pertinentfor traditional music theorists as well. well as a correspondencewith the upperlimit of the voicepitch range within an Americangroup. The presentstudy compared groups of Dutch, British,and Americanlisteners. Contrary to Deutsch'sobserva- 2:30 tions,the perceptualresults of thesethree groups were very similar, and there was no correlationwith individual differencesin vocal range 4pPPS. Pitch center of musical sounds with v•rato. Judith C. within any group.Instead, there were large and systematicdifferences as Brown (Media Lab., MIT, Cambridge,MA 02139 and Wellesley a functionof stimuluscharacteristics (spectral envelope), which further college, Wellesley, MA 02181) and Kathryn Vaughn (MIT, contradictsDcutsch's findings. These results suggest that, rather than Cambridge,MA 02139) derivingfrom a language-basedpitch template, the perceptionof tritonc The determinationof the pitch center of soundsthat are frequency stimuli dependson psychoacousticfactors and individualdifferences in modulatedhas been the focusof a number of previousstudies. The auditory processingwhose nature is not well understoodat present. sourceshave usually been pure tones or syntheticcomplex sounds with [Work carriedout at IPO, Eindhoven.] a well-definedspectral composition. In a musicalcontext these synthetic soundsdiffer in temporal and spectral propertiesfrom the natural 3:30 soundsproduced by stringedinstruments; and it is thesenatural sounds which performersare trained to produceand to perceivein order to 4pPPS. A regional difference within the United States in perception make intonationchoices. Samples consisting of approximatelyI s of of the tritone paradox. Frank Ragozzineand (Dept. acousticsounds produced by a virtuosoriolist playing the notes of Psychol.,Univ. of Californiaat San Diego,La Jolla,CA 92093) C55, A5, and G6 with and without vibrato have been chosen for this A previousstudy [Deutsch,]. Acoust.SOc. Am. 88, S1 (1990)] study.The soundswithout vibrato were then resampledto givefrequen- reporteda strikingdifference in perceptionof the tritoneparadox be- ciesfrom -- 15 to +21 cents,with respectto the geometriccenter of the tween subjectswho had grown up in California and thosewho had sound,with vibrato.Experiments with forcedchoice for pairsof sounds grownin the Southof England:When the Californianstended to hear using musicallyexperienced listeners (including the violist who pro- the patternas ascending the Englishgroup tended to hearit asdescend- ducedthe original sounds)as subjectswill be reported.These experi- ing, and viceversa. One of us (FR), who had grownup in Mahoning mentsinclude a controlset consisting of the comparisonof pitchlevels andTrumbull Counties in Ohiohears the pattern in a fashiontypical of of thesesame sounds played without vibrato. Preliminaryresults with the southernEnglish rather than the Californians.A studywas there- listenerswho are not stringplayers are in accordwith previousresults, foreundertaken to examineperception of thispattern in subjectsfrom findingthat the pitch perceivedis that of the geometricaverage. this region.A statisticallysignificant difference was found between those subjectwhose parents had alsogrown up in this regionand thosewhose 2:4.fi-3:00 Break parents had not. The former group formed a bimodal distribution. and approximatelyhalf the subjectsproducing a histogramsimilar to that obtainedfrom Californiansand the othersproducing one similarto that obtainedfrom the southernEnglish. In contrast,those in the latter 4pPP6. Effeet• of vibratu and vowel matching on choral blend: A group produceda histogramuniformly similar to that obtained from correlation of spectral analyses and perceptual evaluations. Californians.This demonstratesregional differences in perceptionof LawrenceR. Brown (The Recordingand Res. Ctr., The Denver Ctr. this pattern,and alsoan effectof familialbackground.

1860 J. Acoust.Soc. Am., VoL 94, No. 3, PL 2, Sept. 1993 126thMeeting: Acoustical Society of America 1860 THURSDAY AFTERNOON, 7 OCTOBER 1993 CENTURY-SPRUCE ROOM, 1:30 TO 5:30 P.M.

Session4pSA

Structural Acousticsand Vibration: Radiation and Scattering Theory

Joel M. Garrelick, Chair CambridgeAcoustical Associates, 200 BostonAvenue, Medford, Massachusetts 02155

Contributed Papers

1:30 semi-infiniteintegral. The Green'sfunction itself and its firstand second derivativesat the loadingline are obtainedin analyticforms that prove 4pSA1. Convolution formulation of leaky wave contributions to to be usefulin computingthe scatteringmatrix for a rib on the plate. scatteringby plates and by cylindersand shellsof variable curvature. The scatteringmatrix for an isolatedrib is derived.It is shownthat the P. L. Marston (Appl. Res. Lab., Univ. of Texas, Austin, TX waveincident onto one of the n-arbitraryribs on the platecan be written 78713-8029and Phys. Dept., WashingtonState Univ., Pullman, WA as a productof the originalincident wave and a matrix,referred to as 99164-2814) the influencematrix, which reflectsthe alterationof the incidentwave A novel high-frequencyformulation is investigatedthat approxi- on one rib producedby the presenceof the other ribs. The influence matesthe leaky wave amplitudeat the scattererin terms of a spatial matrix is an inverseof a matrix whoseelements are the scatteringma- convolutionof the local incidentwave pressureand a one-sidedline tricesfor singleribs and unit matrices,and it can be expandedas an responsefunction h(s>O)=-ja exp(-as+ikts). Here, s is the prop- infiniteseries which convergesrapidly. Each term in the infiniteseries agationdistance along the flat or curvedsurface, a is the reciprocalof may be interpretedas a generalizedray. Numericalresults are presented the attenuationlength, kt the realpart of the wavenumber, and j = 1 for andcompared with previouswork. [Worksupported by ONR.] equalfluid loadingon bothsides of a platebut j=2 for one-sidedfluid loadingof a shellor for Rayleighwaves on a solid.Application to plane 2:15 wavesincident on cylindricalsurfaces (empty shellor solid) of slowly varyingcurvature yields the followingfar-field amplitude from a leaky 4pSA4. Diffraction effects from the joining of two curved plates. ray propagatinga distanceS on the surface:p•=-2ctpi,•(2•ra•a2/ DouglasRebinsky and Andrew Norris (Dept. of Mech. & Aerosp. kr) •/• exp(-aS•-br/4 + i•1), where a• anda 2 are the radii of curvature Eng., RutgersUniv., P.O. Box 909, Piscataway,NJ 08855-0909) at the launchingand detachmentregions and •/is a geometricalphase accumulation.When a•=a2, the couplingcoefficient G• for a circular Acousticscattering from a fluid-loadedshell consisting of twojoined cylinderderived previously is recovered.The resultcan be modifiedto curvedplates is considered.Asymptotic approximations are madebased situationswhere a variesweakly with curvature.[Work supportedby uponthe assumptionthat the fluidwavelength is muchshorter than the ARL:UTIR&D Programand by ONR.] smallerradius of curvature.A planewave in the fluid incidentupon a line weldat whichthe shellproperties and curvature are discontinuous, but the tangentis continuous,is considered.The problemsimplifies by 1:45 firstassuming that the angleof incidencewith respectto the tangent planeat theweld is not near the critical angle for supersonicmembrane 4pSA2. Retrofiectivebackscattering of soundin water due to leaky waveson either side of the weld. The discontinuitythen generatesa waveson facets,plates, and corner truncations:Approximate theory. diffractedwave field in the fluid which is determinedby solvinga P. L. Marston,S.S. Dodd,and C. M. Loeffler (Appl. Res.Lab., Univ. Wiener-Hopfproblem. This backgroundwave field in turn forcesthe of Texas, Austin, TX 78713-8029) ordinary differentialequations describing the membranewaves. From A leakyRayleigh (or Lamb) waveis knownto be launchedon a fiat their solution, diffraction coefficientsare obtained for the membrane elasticsurface (or plate) in water when the surfacenormal lies near a wavesgenerated on eachcurved plate by the incidentacoustic field. conewhose symmetry axis givesthe k vectorof the incidentsound. If When the incident wave is closeto one of the critical anglesit couples the surfacehas a cornerwith edgesmeeting at anglesof 90ø, 45 ø, 30ø,.., directly to the shell wavesvia curvature,and the interactionof this the wave vectorof the leaky wave is exactlyreversed duc to repeated launchedmembrane wave with the discontinuityresults in scattered reflectionsat the edgesthat form the corner.The resultingleaky radi- membrane wave fields with diffraction coefficients determined in a man- ation is backscatteredtoward the sourceand dependsonly weakly on nersimilar to the previouscase. [Work supported by ONR.] the orientationof the corner.The high-frequencycross section is large sincethe outgoingwave front is fiat. For a suitablycut, randomly 2:30 orientedfacet or metal block, this effect is more likely to be observed thanthe specular reflection since then the normalmust lie on a narrow 4pSAS. Traveling wave decompositionof surfacedisplacements on a rangeof angles.An approximategeometric theory for the amplitudeis cylindrical shell: Numerical evaluation displaying gaided wave given.The mechanismalso applies to circularcylindrical shells with 90ø properties. Gregory Kaduchak,Thomas J. Matula, and Philip L. truncations. Marston (Dept. of Phys., WashingtonState Univ., Pullman, WA 99164-2814)

2:00 Internaldisplacements of sphericalshells subjected to steadysound wavesin waterhave previously been computed by otherresearchers [R. 4pSA3.Scattering of wavesfrom ribs on fluid-loadedplates. Zhang Hicklinget al., J. Acoust.Soc. Am. 92, 499 (1992)]. Suchdisplace- Wangand AndrewNorris (Dept. of Mech. & Aerosp.Eng., Rutgers mentscan be difficultto interpretwith a guidedwave representation Univ., P.O. Box 909, Piscataway,NJ 08855-0909) becauseof thesuperposition of counterpropagating Lamb waves and the A new formulation of the Green's function for a fluid-loaded infinite local responseto the incidentwave. In this researchthe surfacedis- plateunder line loading is presented.The Green's function is expressed placementsof a cylinderwere evaluated since they can be mathemati- explicitlyin termsof a sumof thefive free modes of propagationplus a cally decomposedinto counterpropagatingcircumferential traveling

1861 J. Acoust.Soc. Am., Vol. 94, No. 3, Pt. 2, Sept. 1993 126th Meeting:Acoustical Society of America 1861 waves.(Unlike an analogousdecomposition for spheres,the amplitudes The solutionfor the responseand radiatedpressure from a fluid- in the cylindercase are regular at 0 and 180deg.) By limitingattention loaded, infinite, cylindrical shell with a circumferentialline load, is a to the radialdisplacements of the outersurface, it wasalso possible to classicalproblem in structural acoustics.Although this representsa displaythe responseto short-tonebursts and therebydistinguish be- rather fundamentalproblem, the solutionfor the Crreen'sfunction typ- tweenthe localresponse to the incidentacoustic wave and Lamb waves ically involvea contourintegration for eachspatial point of interest.An launchedon the shell. Both the steady-stateand burst responsesitua- alternativeapproach has beendeveloped which solvesfor the Grecn's tionsclearly manifest waves launched on the shell.These can be easily functionswithout the need to use a contour integral, for every spatial seenfor ka as low as 8 for a thin shell. [Work supportedby ONR.] location, and without the need to introduce structural damping. The approachis a hybrid numerical/analyticalsolution, where the numeri- cal part is basedon an inversediscrete Fourier transform(IDFF) and 2.45 the analyticalpart is the contributionof someof the polesin the solu- 4pSA6.Coupling and launchingof supersonicwaves in elasticshells. tion whichhave to be removedto eliminatethe singularitiesfrom the Andrew Norris and DouglasRcbinsky (Dept. of Mech. & Aerosp. integrandof the IDFT. The singularitiesin the integrandare attributed Eng.,Rutgers Univ., P.O. Box909, Piscataway, NJ 08855-0909) to the real and near real polesof the fluid-loadedcylindrical shell re- sponsein the wavenumber domain. The locationof the singularitiesis The interaction of an acoustic wave with a smooth thin shell in a obtainedusing a numericalsearch algorithm and thereforethe devel- fluid is considered.The couplingmechanism between the acousticfield opedsolution can be usedto more complexgeometries involving the and the supersonicmembrane waves, both longitudinaland shear,is fluid-londedcylindrical shell. Resultswill be presentedwhich match discussedin detail.The couplingis mediatedby the shellcurvature, and well with resultsfound in the literature.[Work sponsoredby ONR.] vanisheswhen the curvaturevanishes. Ray methodsare usedto express the membranewaves by curvedwave fronts with amplitudessubject to a transportequation over the curvedshell surface. The coupling,and 3:45 recouplingor launching,then reduces to solvingan ordinarydifferential 4pSA9. Structural acoustics of cylindrical shells having multiple equationfor theunknown ray amplitude. In essence,the transport equa- layers using the direct global matrix. David C. Ricks and Henrik tion is forced,or "beaten"by the locally phase-matchedbackground Schmidt (Dept. of OceanEng., MIT, Cambridge,MA 02139) field.Explicit expressions are obtained for thecoupling and detachment coefficientson arbitrarilycurved regions. These are combined, using ray A methodhas been developed to computethe responseof cylindri- theoryfor the propagationover the shell,to givethe scatteredfield due rally layered viscoelasticsystems using the direct global matrix ap- to rays travelingover the shell.The generalresults are explicitlytested proach (DGM). The numericalstability of the method allows us to on the cylinderand sphere,for which the ensembleof surfacerays can modelmultilayered shells that haveviscoelastic layers for dampingand be summedinto a resonanceform, and numerical comparisons are made compliantcoatings for decoupling.In this presentation,the methodis with the exactresults for thesecanonical geometries. [Work supported applied to a cylindricalshell having externalfluid loadingand a vis- by ONg.] coelasticlayer of dampingmaterial sandwiched between two solid!ay- ers.The modelcan be excitedby ring forces,point forees,and a point

3.-00-3:15 Break sourcein the fluid. Parameterstudies arc presentedto investigatethe effectof the viscoelasticdamping layer on the variouswave types (flex- ural, membranecompression, and membraneshear). [Work supported 3:15 by ONR.]

4pSA?. Ray acousticmodeling of the surfacefields of u submerged ei•tic cylindricalshell with hem'sphericalendcaps. Jin-Meng Ho ($FA, Inc., 1401 McCormick Dr., Landover, MD 20?85 and Naval Res. Lab., Washington, DC 203?5) 4pSA10. Forward modeling of midfrequency wave propagation in shells. JosephE. Bondarykand Henrik Schmidt (Dept. of Ocean Combiningthe availableray acousticalgorithms descriptive of sub- Eng., MIT, 77 MassachusettsAve., Cambridge,MA 02139) mergedthin cylindricaland sphericalshells, this paperformulates the pressureand velocitydistributions on a hemisphericallycapped cylin- Experimental,bistatic, scattering measurements were made on two, drical shellinsonified by an obliquelyincident acoustic plane wave. As fluid-loaded,cylindrical shells in the frequencyrange of 2

4:15 4pSAg. Response and radiated pressure Green's functions from a fluid-loaded cylindrical shell. J. M. Cuschieri (Ctr. for Acoust. and 4pSA11. Effects of internal attachment on sound scattering from Vib., Dept. of Ocean Eng., Florida Atlantic Univ., Boca Raton, FL cylindricalshells. Y.P. Guo (Dept. of OceanEng., Rm. 5-204,MIT, 33431) and D. Felt (David Taylor Res. Ctr., Bethesda,MD 20084) Cambridge,MA 021219)

1862 J. Acoust.Sec. Am., VoL 94, No. 3, Pt. 2, Sept. 1993 126th Meeting:Acoustical Society of America 1862 This paperdiscusses the effectsof attachmentconditions of internal pitchangles. Comparisons with wave propagation characteristics in an structuralloading on soundscattering from cylindricalshells. The in- unstiffened shell are discussed. ternalloading is modeledas circular elastic plates. It will beshown that strongestscattering results from attachmentthat constrainstangential 5:00 motions in the shell, becausethis kind of attachment interactswith compressionaland shearwaves most strongly, which are dominant 4pSAI4. Responseof submergedcylindrical shells with internalsto wavescontributing to the scatteredfield and are essentiallyassociated an impulseline load. MichaelJ. Utschig,Takeru Igusa,and Jan D. with tangentialmotions in the shell.This is in sharpcontrast to sound Achenbach(Dept. of Civil Eng., NorthwesternUniv., Evanston,IL scatteringfrom structuraljoints in planegeometries, a fiat plate,for 60208 ) example,where the scatteredfield is dominatedby constraintsthat An infinitelylong cylindrical shell containing internal substructures restrictmotions normal to the plate.This suggeststhat slidingjoints in andsubmerged in a fluidis excitedby a shortduration line load.The shell like structuresshould be acousticallybeneficial. responseof the shell,substructure, and fluidis examinedin the fre- quencyand time domains. To gaininsight into the response character- 4:30 istics,two approaches are used. The first is the normal mode approach, wherethe response isexpressed asa Fourierseries in thecircumferential 4pSAI2. On the acousticadvantages of a helical-ringstiffener in a coordinate[M. C. Jungerand D. Feit ( 1986)].In thesecond approach, thin cylindrical shell. Y. F. Hwang (David Taylor Model Basin, the shellis unwrappedinto a two-dimensionalmanifold unbounded in Cardcrock Div., Naval Surface Warfare Ctr., Bethesda, MD boththe longitudinal and circumferential coordinates [Pierce and Kil, J. 20084-5000) Vib. Acoust. 112, 399-406 (1990)]. The responseis expressedas a A conventionalcircular-ring stiffener in a thin cylindricalshell may Fourier transform in the circumferential coordinate. The results of the causeundesirable sound radiation due to the scatteringof subsonic modalapproach are usefulin examiningresonances between the fluid- flexuralwaves. Vibration in eachof a setof disjointedcircular rings may loadedshell and the substructuresand in interpretingthe effectsof the stay within the ring, which resultsin a resonantbuildup that actsas a substructureconnections. The resultsof the secondapproach can be localized excitation of the shell. Furthermore, elastic waves in a cylin- visualizedas wavespropagating around the shell circumferenceand dricalshell tend to propagate,having a plate-wavefront, alongthe axis generatingnear-field acoustic disturbances. A time sequence of contour of the cylinder.A circularring is orientedin the planenormal to the plotsof thenear-field pressure reveals the evanescent and propagating directionof wavepropagation and thereforeit seesthe elasticwave as a acoustic waves associatedwith the shell and substructureresponses. normalincident wave. These rings are separated at a certaindistance in [Worksupported by ONR.] tandem.An incidentwave in the shellmay be reflectedback and forth betweena pairof adjacentrings. Therefore, a circularring may not only 5:15 be an efficientscattered, it couldalso scatter the samewave several times causinga reverberantbuildup in the shellbetween rings, and, conse- 4pSAIS. Echoesfrom a submergedspherical elastic shell coupled to quently,enhance acoustic radiation from the shell. This paper discussed an internalmechanical system. H. Huangand G. Gaunaurd (Naval the technicalrationale to alleviatethese shortcomings by usinga con- Surface Warfare Ctr., White Oak Detachment,Silver Spring, MD tinuoushelical-ring stiflenet in a thin cylindricalshell. 20903-5640) The scatteringof soundwaves by a submergedspherical elastic shell 4:45 coupledto an internaltwo-degrees-of-freedom mechanical system is studied.The problem is solvedusing the classical separation-of-variable 4pSAI3. Wavesin a cylindricalshell stiflened by a helicalrib. K. techniquetaking into accountthe effectsof the trilateralinteraction StevenKim (SignaturesDirectorate, Cardcrock Div., NavalSurface betweenthe incidentwave, the elasticshell, and its internal mechanical Warfare Ctr., Bethesda, MD 20084-5000) system.Numerical results show that echoes from the shell varies signif- In vacuoelastic wave propagation characteristics in an infinitecy- icantlywith the mechanicalproperties of the internalsystem. Particu- lindricalshell stiflened by an infinitehelical rib are investigatedanalyt- larly, the analyticalsolution indicates that at the "fixedbase" resonance ically.Equations of motionof the helicalrib andof the cylindricalshell frequenciesof the internalsystem, the shellmotion stops at the point in helicalcoordinates are developed. They are combined into a singleset where the internalsystem is attached.The scatteredacoustic pressure of equationsusing appropriate boundary conditions. Dispersion curves fieldsat thesefrequencies are analyzedin detail. [Work supportedby of the elasticwaves propagating in the shellare obtainedfor different NSWC.]

1863 d. Acoust.Soc. Am., Vol. 94, No. 3, Pt. 2, Sept. 1993 126thMeeting: Acoustical Society of America 1863 THURSDAY AFTERNOON, 7 OCTOBER 1993 MAJESTIC BALLROOM, 1:00 TO 5:00 P.M.

Session 4pSP

SpeechCommunication: Phonetic Perception

Susan Nittrouer, Chair BoysTown National Research Hospital 555 North 30th Street,Omaha, Nebraska 68151

ContributedPapers

1:00 1:30

4pSPl. Trade-off between burst cues and transition cues in the 4pSP3. Perception of the [m]-[n] distinction in VC syllables perceptionof prevocalicstop consonants:Predictions from acoustical producedby child and adult speakers. Ralph N. Ohde, ChristineW. measurements.Roel Stairsand Ren6 Collier (Inst. for Percept.Res., McMahon, and Katarina L. Haley (Div. of Hear. and SpeechSci., Box P.O. Box 513, 5600 MB Eindhoven, The Netherlands) 552, Station 17, Vanderbilt Univ. School of Medicine, Nashville, TN 37232} Two male Dutch talkersproduced two tokensof eachof 20 stop- vowel syllables(/b,d,p,t,k/followed by/a,i,y,u/}. The releasebursts This researchextends previous developmental studies on the percep- were separatedfrom the voicedparts and four typesof stimuli were tion of the [m]-[n] distinctionin CV syllables[R. N. Ohde and K. created:Burst-only stimuli (BO}, burstlessstimuli (BL), stimuli with Haley, J. Aconst. Soc. Am. 92, 2463(A} (1992}]. With only one ex- cross-splicedbursts, where burst and transitionsindicate conflicting ception,three talkers for eachage level of 3, 5, 7, adult female,and adult male producedVC syllablesconsisting of either /m/ or /n/ in the place-of-articulationinformation (CS}, and original utterances(OR). contextof four vowels/i•eua/. Two productionsof eachsyllable were These stimuli were presentedto 20 subjectsfor identification.Results modifiedusing waveform editing techniques so that the distributionof showthe well-knownvowel-d•endent trade-offbetween burst cues and placeof articulationcues for consonantperception could be determined. transitioncues. An attemptwas made to predictthe confusion matrices Ten adultsidentified the placeof articulationof the nasalfrom several from acousticproperties of releasebursts and formanttransitions using murmur and vowel transitionsegments. Preliminary findings indicate Luce's similarity-choicemodel. Most of the variance (89%} in the that the salienceof the placeof articulationfeature from spectraldis- confusionmatrix for the BO conditionwas explainedusing a spectral continuitycues is substantiallyweaker in VC syllablesthan CV sylla- tilt measureand a spectralcompactness measure. Much of the variance bles,partieulary in children'sproductions. The findingsfor the percep- (80%) for the BL conditionwas explained using frequencies ofF2 and tion of speech segments will be discussedrelative to (1) The F3 at voicingonset and of F2 in the vowel. Using the sameburst and independenceof formanttransitions in the voweland the murmur spec- transitionmeasures for the CS conditionthe explainedvariance dropped trum as cues to place of articulation in VC syllables,and (2) the de- to 40%. Preliminaryresults show better predictions when acoustic mea- velopmentalrole of spectralchange between the voweland the murmur suresare usedwhich integrateover burst and transitions. in syllableacquisition. [Work supportedby NIH, D•.]

1:15 1:45

4pSP2. Acousticsof perceptualcenters in speech. CharlesA. Harsin 4pSP4. A new masked spectrumrepresentation applied to English (Dept. of Psychol.,Univ. of New Orleans,2000 LakeshoreDr., New /r/-/!/ dissimilaritymeasurement. Kiyoaki Aikawa and Reiko A. Orleans, LA 70148) Yamads (ATR Human Information Process. Res. Labs., 2-2 Hikaridai, Seika-cho,Soraku-gun, Kyoto, 619-02Japan) An investigationof the acousticcorrelates of perceptualcenters (p centers) in CV and VC syllableswas conducted.Subjects located the p This paper provesthat a dynamiccepstrum is effectivenot only in centersof the syllablesby placingthe syllablesinto perceptualisochrony automaticspeech recognition, but alsoin enplainingthe speechpercep- with a seriesof 1000 Hz, 5-ms clicks. In all syllablesthe vowel was/a/. tion mechanism.Talker dependencyon the perceptionof American The CV syllablesused the consonants/g/,/r/,/n/,/t/,/d/,/k/, and English/r/-/l/in Japaneselisteners has beenreported [J. S. Logan /g/, while the VC syllablesused the consonants/g/, /r/, and /n/. et ai., J. Acoust.Soc. Am. 89, 874 (1991}]. In orderto interpretthis Consonant duration was varied within each VC combination and within phenomenonwith regardto the acousticalproperties of the stimuli, talker dependencyis assumedto be causedby the acousticaldissimilar- the CV combinationswhich did not beginwith a stop.Energy modu- ity of the stimuli.This paperapplies a dynamiccepstrum to measuring lationsof between3 and 42 Hz were extractedfrom the syllablesand the dissimilarityof the stimuli_The dyrmmieeepgtrum i• a new spectral wcrc weightedaccording to an acousticmodulation sensitivityfunction. representationfor automaticspeech recognition that incorporatesthe The rate, magnitude,and location of energymodulations within the time-frequencycharacteristics of forwardmasking [K. Aikawa et aL, J. syllableswere all found to affectp-center location. In eachsyllable, the Acoust.Soc. Am. 92, 2476(A) (1992)]. This parameterenhances for- largestenergy modulation, which was associatedwith the vowel onset, mant shiftsand suppressesstationary spectral features. In a perception had the greatesteffect on p-centerlocation. In CV syllables,the mod- experiment,identification tests for English/r/-/L/minimal pairs ut- ulation associatedwith the consonanthad a secondaryeffect, while in tered by five talkers were conducted.The dynamic cepstrumand a VC syllablesthe initial vowel modulationwas apparentlythe only de- conventionalcepstrum were comparedfor their performancein mea- terminantof p-centerlocation. The nature of the relevantmodulation suringthe acousticaldissimilarity of the minimalpairs. The/r/-/1/ energy parameterssuggests that they could be acting as information dissimilaritymeasured by the dynamiccepstrum shows a talkerdepen- aboutvelocities and/or accelerationsof articulators,and that p-centers dencyhighly correlated with the talkerdependency of the perception mightsignify an integrationof multiplearticulatory events into a single experimentalresults. [Speech data wereprovided by Dr. D. B. Pisoni, syllabicevent. Indiana University.]

1864 J. Acoust.So(:. Am., VoL 94, No. 3, Pt. 2, Sept. 1993 126thMeeting: Acoustical Society of America 1864 2:00 otherinvestigators reported diverse patterns of dependenciesfor differ- ent stimulusparameters. However, it is not clearif thesedependencies 4pSP5. The perceptualweighting of acousticcues changeswith arespecific only to thespeeded-classification paradigm. The purpose of linguafie experience. SusanNittrouer, Carol Manning,and Gina thisexperiment was to try to generalizeWood's (1975) resultsusing a Meyer (BoysTown Natl. Res.Hospital, 555 North 30th St., Omaha, differentparadigm. The processingdependencies between pitch and NE 68131) placeof articulationusing a speeded-discriminationparadigm were cho- Previousstudies found that children'sjudgments of syllable-initial sen for examination.The basic principle of the experimentwas the /s/ and/[/ are morerelated to the vocalicF2 transitionand lessrelated same,however instead of classifyingthe sounds,subjects had to dis- to the fricative-noisespectrum than are adults'judgments [e.g., Nit- criminatepairs of soundsusing a two-choice("same" or "different") trouer, J. Phon. 20, 351-382 (1992)]. Such resultshave led to a model discriminationtask. The overallpattern of resultswas similar to Wood's of speechdevelopment proposing that children'sweighting of acoustic study,i.e., thereexists an asymmetricdependency between pitch and cueschanges as they gainlinguistic experience. The presentstudy tested placeof articulation.Furthermore, this patternof resultswas observed two requisitesof that model,namely that the perceptualweighting of for "same" as well as "different" reactiontimes. A secondfinding (not acousticcues must be flexible and cannot simply reflect a listener's reportedby Wood) wasthat the error rate data showedthe samepat- auditorysensitivities. Adults and 3-yearolds participated in two tasks: tern of resultsas the reactiontime data. Finally, it appearsthat speeded Identificationtasks, using synthetic fricative noises and eithernatural or discriminationrequires a greaterlevel of selectiveattention and cogni- syntheticvocalic portions; and discrimination tasks, measuring sensitiv- tive processingfor the decisionmaking process than speededclassifica- ity to fricative-noisespectrum and F2 transition.Identification tasks tion. showedthe sameage-related differences found in earlier studieswhen natural vocalicportions were used,but theseage effectswere reduced 2:45-3:15 Break whensynthetic vocalic portions were used. Discrimination tasks showed slightlylarger difference thresholds for boththe fricativenoise and the F2 transitionfor childrenthan for adults,but this age effectcould not 3:15 explainthe ageeffect on the weightingof thosecues for identification.It wasconcluded that the weightingof acousticcues is flexibleboth for 4pSPS.Dialect differences in vowelperception. Alice Faber (Haskins adultsand for children,and that age-relateddifferences in the weighting Labs., 270 Crown St., New Haven, CT 06511), Catherine T. Best of the cuesto/s/and/f/are not explainedby age-relateddifferences in (WesleyanUniv. andHaskins Labs.), and MariannaDi Paolo (Univ. auditorysensitivities. [Work supportedby NIH.] of Utah) Analysisbased on phonemesassumes that "u," for example,in whatevercontext is phonologicallythe same,and that deviations-- 2:15 sometimesextreme--imposed by followingapproximants do not affect 4pSP6. A mapping between trainable generalized properties and the the categorymembership of the vowel.Informed by Best'sperceptual acoustic correlates of distinctive features. Mark A. Johnson (Res. assimilationmodel, which predicts perception of non-nativespeech con- Lab. of Electron.,Dept. of Elec. Eng. and Comput.Sci., Rm. 36-511, trastsfrom their relationshipto nativesegment inventories, this study Cambridge,MA 02139) investigatesthe contrastingpossibility that AmericanEnglish contrasts likepool-pull and heel-hillare perceivedindependently of the contrasts It hasbeen suggested that the acousticcorrelates of distinctivefea- between/u/-/o/and/i/-/•/in other contexts. Connecticut and Utah tures may be most reliably measuredrelative to important acoustic listenersheard productions of both contrastsby speakersfrom both events,or landmarks[K. N. Stevenset al., Proc. Int. Conf. Spoken states;the contrastsare acousticallyless different for Utah than for CT LanguageProcess. 1, 499-502 (1992)]. Theoreticaland empiricalliter- speakers.Listener groups completed Keyword identification,forced- aturein the fieldof phoneticsdescribes many of the acousticcorrelates choicelabeling, and AXB discriminationtasks. There weresystematic of distinctivefeatures, but theseacoustic correlates are often described listener dialect differenceson the keyword and AXB tasks, and both in termsof formantfrequencies and amplitudes,aspiration noise, and groupsdid betteron the CT thanon the UT contrasts.Heel andhill other attributeswhich are difficultfor a speechrecognizer to measure were identifiedwith the vowelsin HID and/or HEED; howeverpool reliably.This paperreports on a preliminaryattempt to compilea table and Npull were identifiedwith AWED or HOED more than with of acousticcorrelates of distinctivefeatures, and to map thesecorrelates FOOD or HOOD. Even whenpool and pull were identifiedwith the to reliableacoustic measurements in the vicinity of an acousticland- samekeyword, one class often contained better exemplars of the key- mark. The acousticmeasurements are simple energy and spectral word than the other, and discriminationwas still abovechance. These changemeasurements, defined in termsof frequencyand timing param- resultssuggest that pool and pull, andheel and hill, minimallydistinct eterswhich may be optimizedfor maximumfeature discrimination us- in Utah, may differprimarily in their distancefrom/•/-/o/and/•/, ing the techniquedescribed by Phillipsand Zue [Proc.Int. Conf.Spo- respectively.[Work supported by NIH GrantNos. HD-01994 and DC- ken LanguageProcess. 1, 795-798 (1992)]. The tableis indexedby 00403.] distinctivefeature, and if an acousticcorrelate is likely to be salientonly in a givenphonological context, the contextis givenas a list of neigh- boringand simultaneous distinctive features. [Work supported by NSF.] 3:30 4pSP9. Productionaml perceptionof work-initiai stops by Korean

2:30 adults. Mi-Ran Kim (Dept. of English,Univ. of Wisconsin,Madison, WI 53706), Charles Read, Keith Kluender, and Andrew Lotto 4pSP7. A speeded-discriminationtask is used to examine processing (Univ. of Wisconsin,Madison, WI 53706) dependenciesbetween pitch and placeof articulation. Anu Sharma, In Koreanthere are threeclasses of stops:Voiceless unaspirated [t], Thomas D. Carrell, and Nina Kraus (Dept. of Commun. Sci. and voicelessslightly aspirated [tb], and voiceless heavily aspirated [thh]. For Disord., Northwestern Univ., Searle Bldg., 2299 N. Campus Dr., theseclasses of stopsproduced by maleand femaleSeoul and Pusan Evanston,IL 60208) speakers,voice-onset time (VOT), amplitudeof aspiration,and f0 of Speededclassification of stimuli varyingalong two independent thefirst five glottal pulses were measured. VOT waslonger for slightly acousticdimensions is frequentlyused to studyperceptual processing of aspiratedthan for unaspiratedstops, and longerstill for heavilyaspi- dependenciesin speech perception. Reaction times are comparedfor rated stops.Unaspirated and heavilyaspirated stops were both pro- differentpresentation sequences to infer perceptualdependencies. Ini- ducedwith significantlyhigher œ0 (more than 30%) than slightlyas- tially,Wood [J. Exp. Psychol. 1, 3-20 ( 1975)]observed a unidirectional piratedstops. Gender and dialect (Seoul versus Pusan) differences in dependencyrelation demonstrating that the processingof placeof ar- thesevariables were also noted. Then, six 12-stepseries of syllables ticulationis dependenton theearlier processing of pitch.Subsequently, differingin VOT (5-82 ms), fundamentalfrequency (100, 125, 150

1865 J. Acoust.Soc. Am., Vol. 94, No. 3, Pt. 2, Sept. 1993 126thMeeting: Acoustical Society of America 1865 Hz), and amplitudeof aspirationnoise ( --33, --21 dB re: vocalicen- followingthe plosion(with the exceptionof increasedFo) but are ergy) weresynthesized. These stops, varying perceptually from [ta] to thoughtto influenceperception by theirappearance in the closurephase [tba]to [t•a], werepresented to 12 native-Koreanlisteners. Results precedingpiGsion [K. Kohler, Phonetics36, 332-343 (1979)]. Kohler indicatethat all threestimulus variables were pereeptuallysignificant [Phonetics41, 1:50-174( 1984)] has claimed that the two piGsire classes for the Koreanlisteners. [Work supportedby NIDCD Grant No. in SwissGerman cannotcontrast initially (where closurefeatures are 00719 and NSF Grant No. DBS-9258482.] not audible), as neither voicingnor aspirationsupports the contrast. This paper reportspreliminary acoustic data {spectrograms)obtained 3.•5 from the natural productionof SwissGerman piGsives by a native speaker.The data indicatethat sonarantsfollowing fortis consonants 4pSPI0. Consonant context affects perceived similarity of North exhibit increasedhigh formant clarity and intensityin relationto the Germanand AmericanEnglish vowels. Winifred Strange,Sonja A. first spectralpeak. Kohler and W. A. van Dominclen[J. Phon. Trent, JanetW. Stack,Xiange Ling, and Alba I. Rodriguez (Dept. of 365-381 (1987)] show a similar acousticfeature to be associatedwith Commun. Sei. and Disoral., Univ. of South Florida, 4204 E. Fowler global "tense voice" manner in the vowelssurrounding intervoealic Ave., Tampa, FL 33620-8150) piGsives.It is thussuggested that the observedacoustic feature is oneof tensionassociated with the productionof fortis plosivesin SwissGer- Severalcurrent theoriesof L2 learningattempt to predict relative man, and that this is available to maintain the fortis/lenis contrast difficultiesin learningto producephonetic contrasts of a foreignlan- initial position. guageon the basisof the non-nativephones' phonetic similarity to native phonemecategories. In this study,monolingual speakers of American English (AE) were askedto categorize(into AE vowel categories) 4:30 instancesof the 14 North German (NG) vowelsand to judge their goodness-of-fiton a seven-pointscale. Multiple tokensof eachvowel 4pSPI3. Intelliglbility of Mandarin speakersof English: Correlation wereproduced in/C-vowel-t/syllables (whereC=/b,d,g/) in a carrier of acousticand pereeptua measures. C. Wardrip-Fruin and A. sentence.Results indicated that both the proportionof assignmentsto Constantinou (Dept. ofCommun.Disord. and Programin Linguistics, particularAE categoriesand the gcodness-of-fitratings were influenced CaliforniaState Univ., Long Beach,CA 90840) significantlyby the initial consonantalcontext. While front roundedNG Wave duration and wave peak amplitude were measuredfor 10 vowelswere categorizedmore often overall as back roundedAE vowels Mandarin speakersof Englishand five nativeEnglish speakers. Results than as front unroundedAE vowels,front unroundedresponses were revealedsignificant differences between the two groupson theseacoustic significantlygreater for front roundedvowels in labial contextthan in variables.Discriminant function analysisresulted in 12 (80%) of 15 alveolar and velar contexts. In addition, the categorizationof several subjectsbeing classified correctly in their respectivelanguage groups NG vowelsindicated significant individual differences among subjects in basedon the wave duration and wave peak amplitude measures.A categorizationpatterns. Implications of thesefindings for conceptual- secondexperiment, with the 10 Mandarin subjectsas speakersand 231 izationsof nativeqanguagephonetic "prototypes" as discussed. nativeEnglish speakers as listeners,ranked the intelligibilityof each speaker.A regressionanalysis revealed high correlation{r=0.897) be- 4.'OO tweenacoustic and perceptualmeasures; measurements of amplitude waveduration account for 89.1% of the variationin intelligibilityand 4pSP11. A dynmic model for the temporal properties of Swedish. measurementsof peaksin wave amplitudeaccount for 68.5% of the Bertil Lybergand BarbroEkholm (Telia Res. AB, S-136 80 Haninge, variationin the speechsamples. These findings suggest that intelligibil- Sweden ) ity of Mandarinspeakers of Englishis a functionof acousticparameters The segmentduration varies dependingon a number of linguistic of prosody. and nonlinguisticfactors. At the word and phraselevels, the segment

durationis foundto vary dependingon the positionin the work and in 4:45 the phrase.The positionaleffects on segmentduration have been studied by severalinvestigators and, for somelanguages, models have been 4pSP14. Final stop devoieingin Polish: Incompleteneutralization. hypothesizedin order to describethe durationof speechsegments in Bo•cnaTieszen and CharlesRead (Dept. of Linguistics,Univ. of differentpositions in wordsand phrases.The greatestpositional effect is Wisconsin, 1220 Linden Dr., Madison, WI 53706) the phenomenonof final lengtheningthat appearsto be of considerable generalityas a phoneticphenomenon. Most computationalmodels for In Polish,as in someother Slavicand Germaniclanguages, word- segmentduration are, however, static, i.e., the durationalproperties are final obstruentsare devoiced.Three monolingual speakers in Krakow modeledat a certainspeech rate. In this investigationthe segmentdu- recordeda sampleof ine minimal pairs containingfinal /p,t,k,b,d,g/ ration is studiedat differentspeech rate and with focusassignment precededby eachof the vowels/i,a,u/in a meaningfulcarrier sentences. systematicallyvaried along the sentence.The segmentduration values Eachword wasfollowed by a voicelessobstruent, in onecase, and by a are studied by means of both reiteratant speechand ordinary read vowel in another.The speakershad also recordedsome of the same speech.A tentativedynamic model for the segmentduration is pre- wordsin the sameenvironments in a narrativepassage. Three durations sented. were measured:Of the precedingvowel, of the stop closure,and of glottalpulsing into the closure.For all threespeakers and all environ- ments,the durationsof the precedingvowel and of the stopclosure did 4:15 not differsignificantly between underlyingly voiced and underlyingly 4pSPI2. Acoustic correlates of the fortis/lenis contrast in Swiss voicelessstops. However, for all threespeakers and all threeplaces of German piGsives. Scan A. Fulop (Dept. of Linguistics,Univ. of articulation,glottal pulsinginto the closurewas significantly longer for Calgary,2500 UniversityDr., Calgary,AB T2N IN4, Canada) underlyinglyvoiced stops than for their underlyinglyvoiceless counter- parts.This outcomeheld for the wordsin the narrativepassage as well Featuresof articulatorytension in piGsives,such as increasedclosure as those in the carrier sentences. These results contrast with those ob- duration, have not beenshown to be perceptuallysalient in the time tainedby Slowiaczekand Dinnsen[J. Phon.13, 325-341 (1985)].

1866 J. Acoust.Soc. Am., VoL 94, No. 3, Pt. 2, Sept. 1993 126thMeeting: Acoustical Society of Amedca 1866 THURSDAY AFTERNOON, 7 OCTOBER 1993 COLUMBINE ROOM, 12:55 TO 5:00 P.M.

Session4pUW

Underwater Acoustics: Signal Processing II

Nicholas C. Makris, Chair Naval ResearchLaboratory, Washington,DC 203 75

Chair's Introduction--12:55

ContributedPapers

1:00 In shallowwaters, the effectivevertical aperture of an array com- posedof horizontaland verticalsegments may be greaterthan the water 4pUWI. Serpentinearray processing.J. RobertFricke (Dept. Ocean column depth. The extendedvertical aperture leads to better decompo- Eng., MIT, Rm. 5-218,77 MassachusettsAve., Cambridge,MA 02139) sitionof bottom-interactingnormal modes and hencebetter range-depth Oftenone must determine the wave-numberspectra of complicated localizationcompared with the performanceof the vertical subarray spatial wave fields, which contain significantenergy propagatingin a alone.The conditionsunder which the effectivevertical aperture gives broad rangeof directions.In this casea singlelinear array must be improvedlocalization performance over a vertical array spanningthe steeredto endfireto computesome of the wavenumbers of interest.To watercolumn are demonstrated.The effectof sourcefrequency, ratio of alleviatethis need a multilineararray, e.g., a Mill's Cross,is oftenused. horizontalto verticalarray length,and bottomproperties on localiza- This paper discussesa broadbandwave-number spectral estimation tion performanceare discussed. methodologywherein the array elementsmay be placedin an arbitrary serpentinepattern. The array processingtechnique is a modified radon 1:45 transformfor serpentinearrays, which may be interpretedas a plane wavedecomposition. The elementsof the serpentinearray are projected 4pUW4. Digital acoustic video image transmission system for onto virtual linear arrays steeredin the intendeddirection for plane- deep-sea research submergence vehicle "SHINKAI 6500." Toshio waveestimation. A weightingfunction is computedto compensatefor Tsuchiya,Yasutaka Amitani, Hiroshi Ochi (Deep SeaTechnol. Dept., multipleserpentine array segments being projected onto a singlevirtual JapanMarine Sci. and Technol. Ctr., 2-15 Natsushima-cho,Yokosuka, array segment.The compensationvaries with each steeringangle. The 237 Japan), and Michiya Suzuki (NEC Corp., Fuchu, 183 Japan) lengthof the virtual lineararray at eachsteering angle determines the resolutionof the serpentinearray. [Work supportedby ONR.] High-speedvideo image transmission from a researchsubmersible to the mothership is desirableto facilitateeffective deep-sea research by a submersible.Therefore, a digital acousticimage transmissionsystem 1:15 wasdeveloped, and was installedin the manneddeep-sea research sub- mergencevehicle "SHINKAI 6500" of the JapanMarine Scienceand 4pUW2. Large sets of frequency hopped codes with nearly ideal TechnologyCenter. This systemwhich adopts4-DPSK modulation orthogonality properties. Scott T. Rickard and J. Robert Fricke with a carrier frequencyof 20 kHz, has a communicationcapability of (Dept. Ocean Eng., MIT, Rm. 5-218, 77 Massachusetts Ave., 16 kbit/s and is able to transmita color-stillimage of 256X240 pixels Cambridge,MA 02139) in 8 s. Its communicationrange is more than 6800 m. In order to transfer a high-qualitycolor image in a short time, (a) a wide band Significantperformance improvements would be realized in many transducer, that doubles the transmission band, (b) a DCT- (discrete sonarsystems if only it werepossible to havemultiple pings in the water cosinetransform) based image coding technique that reducestransmis- at any giventime. The useof orthogonalfrequency hopped codes is one sion data volume, and (c) an adaptiveequalizer and phasecontroller, way to achievemultiple, simultaneousaccess. These codes can be de- that improve communicationquality and Doppler compensation,are signed to have nearly ideal autoambiguityand low cross-ambiguity employed.Results of a performancetest (variousvideo images)were properties.In someapplications it is desirableto usecodes drawn from successfullyreceived from the "SHINKAI 6500" from a depthof 6500 a very largeset, say O( 101300).This paperdiscusses how sucha setcan m to the surfacevessel. After a successfulperformance test, this system be generated.Specifically, the trade-off betweenauto/cross ambiguity will probablybe installedin the "SHINKAI 6500," and new biological properties,time-bandwidth product, and codeset sizewhen generating or geologicalexperiments will be carried out by the systemin the deep largesets are explored.For codeswith N frequencyhops, the focusis on sea of the western Pacific Ocean. techniquesfor generatingmore than O(N) codes,which characterizes most codegeneration techniques. Others are nonlinearin N. In partic- ular,the Golomb-Costas method generates O(N 2) codes.These codes 2:00 are "full", whichmeans every available frequency is usedin everycode. TheReed-Solomon method, in contrast,generates O(N k) codes,where 4pUWS. Detection of a submergedobject insonifiedby beach noise. k is a trade-offparameter proportional to sidelobelevel in the cross- Nicholas C. Makris, William A. Kuperman (Naval Res. Lab., ambiguityfunction. Reed-Solomon codes, however, are not "full." The Washington,DC 20375), and Frank Ingenito (SACLANT Undersea trade-offbetween fullness and numberof codesis illustrated.[Work Res. Ctr., La Spezia,Italy) supportedby C. S. DraperLaboratory.] In a previouspaper, numerical simulations were performedwhich demonstrated that a submerged object insonified by surface noise in an

1:30 oceanwaveguide can be detectedat low to mid frequencyfor realistic arrayswithin about l-km range[Makris et al., J. Acoust.Soc. Am. 91, 4pUW3. Effective vertical aperture for three-dimensionalarrays in 2416 (A) (1992)]. For the presentpaper, an investigationinto the shallowwaters. ChristopherW. Bogartand T. C. Yang (Naval Res. possibilityof detecting a submergedobject insonifiedby low- to mid- Lab., Washington,DC 20375) frequencybeach noise in an ocean waveguidewas carried out. Model

1867 J. Acoust. Soc. Am., Vol. 94, No. 3, Pt. 2, Sept. 1993 126th Meeting: Acoustical Society of America 1867 beachnoise is definedas a one-dimensionalarray of uncorrelatedsur- search,Program Element 61153N, with technicalmanagement pro- facesources and the detectabilityof the objectis investigatedfor various vided by NRLSSC.] orientationsof the sensingarray axis,beach axis, and object.

3:00-3:15 Break 2:15

4pUW6. Time compressionprocessing of M sequencesfrom the 3:15 Heard Island Feasibility Trial. Garry J. Heard (Defence Res. 4pUW9. Signal-to-noiseimprovement for higher-ordercorrelators EstablishmentPacific, Bldg. 199, FMO Esquimalt,Victoria, BC V0S with one-dimensionalprefiltering. Lisa A. Pfiug (Naval Res. Lab., lB0, Canada) and Ian Schumacher (JASCO Res. Ltd., Sidney,BC StcnnisSpace Center, MS 39529-5004),Julictte W. Ioup,George E. V8L 3S1, Canada) Ioup (Univ. of New Orleans, New Orleans, LA 70148), and Canadawas one of nine participatingcountries in the Heard Island Robert L. Field (Naval Res. Lab., Stennis Space Center, MS FeasibilityTest (HIFT) and had two towed-arrayreceivers operating, 39529-5004) one in the Pacificand one in the Atlantic.Due to the extremelylong Previouswork by the authorshas shown that prefilteringwhen used propagationpaths the Canadiandata werefound to haverelatively low in conjunctionwith higher-ordercorrelators possesses potential detec- signal-to-noiseratios that complicatedthe M-sequencetime-compression tion advantagesover the ordinarycross-correlation detector for band- correlationprocessing. An analysiswas carried out to determineif time- limitedtransient signals in noisefor active(known source) and passive compressionprocessing of the datawas possible with the low signal-to- (unknownsource) sonar. Preliminary simulation results have been pre- noiseratio data available.A meansof removingDoppler variations sented[Ioup et al., •. Acoust.Soc. Am. 92, 2417(A) (1992); Ioup fromthe data based on phase tracking the heterodyned baseband signal et al., Proceedingsof the IEEE SignalProcessing Workshop on Higher- wasdeveloped and applied to severalof the strongerHIFT receptions. Order Statistics,7-9 ]'une 1993]. Additional researchhas been com- Useful correlationresults were obtainedusing this technique.Initial pleted,including a systematicand quantitative study using three differ- estimates of the travel time differences for the dominant acoustic arriv- entfilter levels. Eight test signals are presented in thestudy: Several very als were obtained from the correlations. low-frequencysignals, a pulse,a 50-Hzsinusold, a resonatingsinusold, a FM linearsweep, and a nonlinearFM sweep.SNR gaincomparisons 2:30 betweenthe detectors are made for Pd=0.5 and P/a=0.001. Significant SNR gainsare evidentfor both the known and unknownsource models 4pUW7. Noise cancellation,environmental focusing, and source with thetricotrelation detector exhibiting the largest gains. For all the localization.Michael D. Collins (Naval Res.Lab., Washington,DC testsignals, the tricorrelation detector outperforms the cross-correlation 20375) detectorfor the unknownsource model, and outperforms the matched The ability to localizean acousticsource in the oceanis oftenlimited filter for sevenof the eighttest signals for the knownsource model. by ambientnoise and other typesof noise.If the natureof the noiseis [Researchsupported by Officeof NavalResearch, Program Element at leastpartially understood, this limitation can be reduced significantly 61153N,with technicalmanagement provided by NRLSSC.] by includingthe noiseparameters in the spaceof searchparameters. The performanceof this approachhas been tested in simulationsinvolv- 3:30 ing a source buried in ambient noise and interference noise due to a sourceat a known location. Uncertainty in the ocean environmentis 4pUW10. Minimum entropy deconvolutionof underwater acoustic anotherlimiting factor that can be reducedby expandingthe spaceof transients. Michael K. Broadhead (Naval R es. Lab., Code 7173, searchparameters [Collins and Kuperman,]'. Acoust.Soc. Am. 90, StennisSpace Center, MS 39529-5004) 1410-1422(1991)]. By includingthe source,noise, and environmental Theminimum entropy deconvolution (MED) methodJR. Wiggins, parametersin the searchspace, it is possibleto localizean acoustic Gcoexploration16, 21-35 (1978)],is usedto producesource signature sourceburied in noisein an uncertainenvironment. Special cases of this estimatesfrom underwater acoustic transients, which has application in optimizationproblem include source localization, tomography, geoa- the passivesonar classification problem. The Green'sfunction, repre- cousticinversion, localization, and imagingwith acousticdaylight sentingenvironmental distortion effects, is treated as a non-Gaussian [Buckinghamet al., J. Acoust.Soc. Am. 91, 2318(A) (1992)]. randomprocess. The MED methodimplemented in thispaper leads to a one-parametermodel that doesn'trequire accurate knowledge of the 2:45 sourcelocation and environmentalparameters, or the computationof Grcen'sfunctions. Results from applyingthe MED methodto single- 4pUW8. Theoreticalsignal-to-noise gain formulasfor energysignal sensor,broadband ocean acousticmeasurements are shown, where bicorrelationand tricotrelation detection. Lisa A. Pfiug (Naval Res. sourcesignature estimate correlation coefficients range between 0.87 to Lab.,Stennis Space Center, MS 39529-5004),George E. Ioup (Univ. 0.91.The method is alsoapplied to realisticsimulations, produced with of New Orleans,New Orleans,LA 70148), RobertL. Field (Naval a parabolicequation (PE) model,using a sourcepulse that was longer Res. Lab., StennisSpace Center, MS 39529-5004),and JulietteW. andmore complex than the measured source. Source signature estimate Ioup (Univ. of New Orleans,New Orleans,LA) correlationcoefficients ranged between 0.95 and0.99. The technique In the pastthe authorshave examined energy signal detection and assumesthat the input random process is non-Gaussian,which is jus- tifiedby highkurtosis values of thecomputed (PE) Green'sfunctions timedelay estimation performance of ordinary and higher-order corre- associatedwith thisdata set. [Work supportedby Officeof NavalRe- lationsusing Monte Carlo simulationsand hypothesistesting [for ex- acarch, with technical managementprovided by the Naval Research ample,Pfiug et al., J. Acoust.Soc. Am. 91, 2763 (1992)]. For some Laboratory.] circumstanceshigher-order detector performance and SNR gainscan be predictedtheoretically based on third- and fourth-ordermoments. SNR gainformulas for higher-orderdetectors have been derived for a prob- abilityof detectionof 0.5 andare discussedin thispaper. Comparisons 4pUWII. The effects of a bottom-limitedocean on signal of thesetheoretical results are made to simulationswith a modelsignal kurtosis•Applications to tricorrelation detection and minimum whosemoments can be varied.Validity of the theoreticalresults is entropy deconvolutionof broadbandsignals. R. L. Field and •. H. confirmedwith eight diverse test signals which have been used in pre- vioussimulation studies. The formulasmake possible the calculation of Leclcre (Naval Res. Lab., Code7173, StennisSpace Center, MS 3952%5004) minimum third, and fourth-order moment values neededfor the bicor- relationand tricorrelationdetectors, respectively, to outperformthe As signalspropagate in theocean their temporal and spectral fea- cross-correlationdetector. [Research supported by Officeof Naval Re- turesvary as a functionof spaceand time.This is especiallytrue in

1868 J. Acoust.Soc. Am., Vol. 94, No. 3, Pt.2, Sept.1993 126thMeeting: Acoustical Society of America 1868 bottom-limitedenvironments where the signal may encounter numerous transfer function could be extracted from the fourth-order cumulant boundaryinteractions with significantloss due to absorption.This en- spectrum.Results for three elasticspherical objects in motion will be vironmentaldistortion can have a significanteffect on the ability to discussed.Specifically, performance results for the extractionof the detectand classify broadband signals. A broadbandparabolic equation Dopplercomponent, phase, and magnitudeof the object'stransfer func- modelis usedto predictsignal distortion over a 25-150-Hz bandwidth tion from the fourth-ordercumulant spectrum will be comparedwith in both range-independentand downslope,bottom-limited environ- classical first- and second-order methods. merits.Signal kurtosis is usedto characterizesignal distortion in range anddepth. Comparisons are made between the kurtosis predicted by the 4:30 modeland that estimatedfrom experimentaldata. It is shownthat the 4pUWI4. Shallow water reverberation, signal motion loss, and model,together with goodenvironmental information, can accurately acousticnavigation: A preliminarystudy for autonomousunderwater predictsignal kurtosis as a functionof rangeand depthin the ocean. vehicletarget detection. W. Kenneth Steward,Xiaoou Tang, and The significanceof the variationof signalkurtosis is discussedin terms DezhangChu (Dept. of Appl. OceanPhys. and Eng.,Woods Hole of the tricotrelationdetector and minimumentropy aleconvolution of Oceanogr.Inst., WoodsHole, MA 02543) broadbandsignals. [Work supportedby Officeof Naval Research,Pro- gram Element61153N, with technicalmanagement provided by the It is usuallydifficult to useautonomous underwater vehicles (AUV) Naval ResearchLaboratory.] for locatingtargets in shallow-waterocean environments due to the strongwave surge and multipath acoustic reverberations. A preliminary 4:00 studyof someenvironmental effects unique for a shallow-watersound channelhelps place bounds on possiblesolutions and reduceprogram 4pUW12. Cross-spectral matrix estimation efteeLs on adaptive uncertainty.Accordingly, three interrelated issues are addressedin this beamforming. David E. Grant, Jonathan H. Gross, and Mimi Z. paper: Signal maskingby shallow-waterreverberation, signal loss Lawrence (Appl. Res. Labs., Univ. of Texas, P.O. Box 8029, Austin, causedby extremeplatform motions, and shallow-wateracoustic navi- TX 78713) gation.A modelestimating the signalmotion loss and the averagere- verberationintensity in the shallow-waterenvironment is developed. Adaptivebeamforming algorithms, which use CSM (cross-spectral The computersimulation of multisensornavigation serves not onlyas a matrix) datato calculateoptimum weights, are sensitiveto the number precisevehicle-positioning device but alsoas the platformmotion data of unsmoothedCSM samplesused in the CSM estimate.Assuming that input for the model.As a resultof the shallow-waterexperiments and the samplesused in the CSM estimateare independentidentically acousticmodeling, conclusions of thispreliminary study are ( 1) SML is Gaussiandistributed with zeromean, it is shownthat the outputpower not the dominantfactor for sonarsin the frequencyrange of interest fromthe estimated CSM is biasedlow relative to theoutput power from ( > 200 kHz) with respectto targetdetectability, (2) beampatterns can the real CSM. Usingdata from a horizontalline array deployedin a be manipulatedto effectivelyreject most interferences caused by surface shallowwater, high noise environment, the adaptivebeamformer output reverberationand noise,and (3) a multisensornavigation filter is prac- powerwith variousnumbers of samplesused in the CSM estimatehas tical evenwith limited sensordata quality. beenmeasured. The numberof CSM sampleswas varied by changing the time-bandwidthproduct. The measuredmedian beam noise levels 4:45 arecompared with thetheory. Since the data do notfit theassumptions statedabove, the agreement is notexact. However, the general trends of 4pUWlS. Spatial coherencemeasurement of sound in the northwest the data and theoryagree quite well. Conclusionsare drawnabout the Pacific Ocean. Dinghua Guan, Ruichao Zhu, Renhc Zhang, and numberof samplesthat shouldbe usedfor a CSM estimateto be reli- Yaoming Chcn (Inst. of Acoust., Acadcmia Sinica, P.O. Box 2712, able, and about the stationarityof the data within the time-bandwidth Beijing 100080,People's Republic of China) integrationused in the CSM estimates.[This work is supportedby the U.S. Navy Spaceand Naval Warfare SystemsCommand.] An experimenton the transversehorizontal spatial coherenceof soundpropagating in the oceanwas performedjointly by Chineseand Russian acousticians in the northwest Pacific Ocean in June 1990. Three 4:15 hydrophoneswith spacingsof 270 and 130 m were put in the water at 4pUW13. Results on the identificationof acousticobjects in motion a 30-m depth. The acousticsource with four cw (from 109 to 860 Hz) from the fourth-ordercumulant spectrum. Roger F. Dwyer (Naval and a broadbandpseudorandom noise signal was drifted at a depthof UnderseaWarfare Ctr., New London, CT 06320) 100m. Part of the measurementresults of up to 140km are presented in this paper. It seemsthat the spatial coherencewas related to the It wasreported [J. Acoust.Soc. Am. 93, 1460-1465( 1993)]that the amplitudeof the receivedsignals and risesconsiderably in convergence Dopplercomponent and both the magnitudeand phaseof an object's zones.

1869 J. Acoust.Soc. Am., Vol. 94, No. 3, Pt. 2, Sept. 1993 126th Meeting:Acoustical Society of America 1869 THURSDAY AFTERNOON, 7 OCTOBER 1993 SAVOY ROOM, 1:30 P.M.

Meeting of Accredited Standards Committee S1 on Acoustics

to be held jointly with the

U.S. Technical Advisory Group for ISO/TC 43 Acousticsand IEC/TC 29 Electroacoustics

G. S. K. Wong, Chair S1 Institutefor National MeasurementStandards (INMS), National ResearchCouncil, Ottawa, Ontario K1A OR6, Canada

H. E. von Gierke, Chair U.S. TechnicalAdvisory Group (TAG)for ISO/TC 43, Acoustics,1325 MeadowLane, YellowSprings, Ohio 45387

V. Nedzelnitsky,U.S. TechnicalAdvisor (TA) for IEC/TC 29, Electroacoustics National Institute of Standardsand Technology(NIST), Building 233, Room A149, Gaithersburg,Maryland 20899

StandardsCommittee S1 on Acoustics.Working group chairs will report on their preparationof standardson methodsof measurementand testing,and terminology,in physicalacoustics, electroacoustics, sonits, ultrasonics, and underwatersound. Work in progressincludes measurement of noisesources, noise dosimeters, integrating sound-level meters, and revisionand extensionof soundlevel meter specifications.Open discussionof committeereports is encouraged.

The international activities in ISO/TC 43 Acoustics,and IEC/TC 29 Electroacoustics,will also be discussed.The chairs of the respectiveU.S. TechnicalAdvisory Groups for ISO/TC 43 (H. E. vonGierke), andIEC/TC 29 (V. Nedzelnitsky),will report on currentactivities of theseTechnical Committees. Reports will be givenon the resultsof the last methodsof ISO/TC 43 (in Oslo,Norway, held from 31 May-4 June 1993), and of IEC/TC 29 (in Oslo,Norway, held from 24-28 May 1993).

Scopeof SI: Standards,specifications, methods of measurementand test, and terminologyin the field of physicalacoustics includingarchitectural acoustics, electroacoustics, sonics and ultrasonies,and underwatersound, but excludingthose aspects which pertain to biologicalsafety, tolerance, and comfort.

THURSDAY AFTERNOON, 7 OCTOBER 1993 SAVOY ROOM, 3:00 P.M.

Meeting of Accredited Standards Committee S3 on Bioaeousties

to be held jointly with the

U.S. TechnicalAdvisory Group (TAG) Meetingsfor ISO/TC 43 Acoustics,IEC/TC 29 Electroacoustics,and ISO/TC 108/SC4 Human Exposure to Mechanical Vibration and Shock

J. D. Royster, Chair S3 4706 ConnellDrive, Raleigh,North Carolina27612

H. E. von Gierke, Chair U.S. TechnicalAdvisory Group (TAG) for ISO/TC 43, Acousticsand ISO/TC 108/SC4, Human Exposure Mechanical Vibration and Shock 1325 Meadow Lane, YellowSprings, Ohio 45387

V. Nedzelnitsky, U.S. Technical Advisor (TA) for IEC/TC 29, Electroacoustics NationalInstitute of Standardsand Technology(NIST), Building233, RoomA149, Gaithersburg,Maryland 20899.

StandardsCommittee S3 on Bioacoustics.The currentstatus of standardsunder preparation will be discussed.In additionto thosetopics of interest,including hearing conservation, noise, dosimeters, hearing aids, etc., consideration will begiven to new standardswhich might be neededover the nextfew years. Open discussion of committeereports is encouraged.

Theinternational activities in ISO/TC 43 Acoustics,and IEC/TC 29 Electroacoustics,and ISO/TC 108/SC4Human Exposure to MechanicalVibration and Shock, will alsobe discussed.The Chairsof the U.S. TechnicalAdvisory Groups for ISO/TC 43

1870 J. Acoust.Soc. Am., VoL 94, No. 3, Pt. 2, Sept.1993 126thMeeting: Acoustical Society of America 1870 (H. E. yonGierke), and IEC/TC 29 (V. Nedzelnitsky),will reporton currentactivities of theseTechnical Committees and Subcommittees.Reports will be givenon the resultsof the lastmeetings of ISO/TC 43 (in Oslo,Norway, from 31 May-4 June 1993),and of IEC/TC 29 (in Oslo,Norway, from 24-28 May 1993).A reportwill be givenon the ISO/TC 108/SC4meeting held in London,United Kingdom,from 29 March-I April 1993.

Scopeof S3: Standards,specifications, methods of measurementand test,and terminologyin the fieldsof mechanicalshock and physiologicalacoustics, including aspects of generalacoustics, shock, and vibrationwhich pertain to biologicalsafety, tolerance and comfort.

THURSDAY EVENING, 7 OCTOBER 1993 GRAND BALLROOM D/E, 7:30 TO 8:30 P.M.

Session 4cAB

Animal Bioacoustics,Acoustical Oceanography, and UnderwaterAcoustics: Panel Discussionon Effectsof Noise on Marine Mammals

William C. Cummings,Chair Tracor,Inc., 9150 ChesapeakeDrive, San Diego,California 92123-1003

FRIDAY MORNING, 8 OCTOBER 1993 MAJESTIC BALLROOM, 10:00 A.M. TO 12:00 NOON

Session 5aMU

Musical Acoustics: Theatrical Performance

Ronald C. Scherer, Chair Recordingand ResearchCenter, Denver Center for the PerformingArts, 1245 ChampaStreet, Denver, Colorado 80204

Invited Paper 5aMUI. Contrastingspeech and singing•Performancedemonstration. Ronald C. Scherer,Tony Church (Denver Ctr. for the Performing Arts, 1245 Champa St., Denver, CO 80204), and Renee SkravanosRoot (Univ. of Colorado, Denver, CO 80204)

Nonamplifiedvoice and speechfor the stageimposes different production requirements than during conversationalspeech. Tony Church,noted Shakespearean actor and Dean of the NationalTheatre Conservatory, and ReneeSkravanos Root, operatic and recital artist and singingteacher, will demonstratevoice and speechproduction for the stagerelative to contrastsof communicationintent and requirementsfor audibilityand intelligibility.Open discussion and researchconnections will accom- pany the demonstrations.

1871 J. Acoust. Soc. Am., Vol. 94, No. 3, Pt. 2, Sept. 1993 126th Meeting: Acoustical Society of America 1871 FRIDAY MORNING, 8 OCTOBER 1993 DENVER ROOM, 8:40 TO 11:30 A.M.

Session SaNS

Noise: Low-Frequency Sound, Propagation, and Other Noise Topics

Daniel L. Johnson, Cochair EG&G SpecialProjects, P.O. Box 9100, Albuquerque,New Mexico 87119

Robert D. Bruce, Cochair CSTI, 15835 Park Ten Place, Suite 105, Houston, Texas 77084-5131

Chair's Introduction--8:40

Cont•buted Papers

8:45 injectionflow ratesand far-fieldsound pressure levels were determined. In addition,correlations between sound pressure levels and typical res- SANS1. Crosswlndeffects on acoustic propagation. Mark Sprague, idential wall vibrationlevels were alsosimilarly determined.From these Richard Rasper (Phys. A½oust.Res. Group, Univ. of Mississippi, relationships,the potential for flare noise-inducedvibrations to cause University,MS 38677), and V. E. Ostashev (Inst. of Atmospheric cosmeticdamage to nearbyhouses will be discussed. Phys.,Russian Academy of Sci.,Pyzhevskii 3, Moscow109017, Russia)

Ray theory saysthat a ray movingin a crosswindwill drift out of the 9:30 plane of propagation,and that this effectcan be significantwith high windspeedsand over long propagation distances. White andLi [Michael SANS4. Low-frequencynoise-induced vibration of housingstruetures. J. White and Y. L. Li, J. Acoust. Soc. Am. 92, 2405 (A) (1992)] and BennettM. Brooks (BrooksAcoust. Corp., 27 Hartford Tpk., Vernon, Wilson [D. Keith Wilson, $. Acoust. Soc. Am. 92, 2405 (A) (1992)] CT 06066) developedtwo-dimensional fast-field programs (2DFFPs) to calculate the sound pressurelevels of windy atmospheres.They reportedthat It is known that moderatelevels of very low-frequencynoise (less than 20 Hz) can induce vibration in elements of common residual hous- crosswindeffects were negligiblefor the casesthey consideredand that a one-dimensionalstationary phase solution yields accurate results. Ray ing structures.Measurements of low-frequencynoise caused by nearby analysisof the two-dimensionalphase space used in the 2DFFP indi- largeindustrial facilities were made at severaldifferent types of houses. catesthat there is a small region that contributessignificantly to the These data are comparedto criteria for the perceptibilityof noise- soundlevel. In the presenceof a crosswind,the one-dimensionalsta- inducedvibration. The subjectiveperception by residentsof housevi- tionaryphase approximation does not includeall of thisregion. 2DFFP bration,and the independentobservations of others,correlate well with the noise criteria. In addition, measurementsof house vibration were calculationsfor realisticwindspeeds that showcrosswind drift are pre- sented,and the 2DFFP calculationsare comparedto the calculationsof madeat sometest locations and are comparedto both noiseand vibra- tion criteria. a one-dimensionalstationary phase approximation.

9:45

SANS2. Low-frequency sound waves associated with avalanches, 5aNSS. The Lookup program for prediction of noise levels outdoors. atmospheric turbulence, severe weather, and earthquakes. Alfred J. Michael J. White and Y. L. Li (U.S. Army ConstructionEng. Res. Bedard, Jr. (Natl. Oceanic and Atmospheric Admin., Wave Labs., P.O. Box 9005, Champaign,IL 61826-9005) PropagationLab., 325 Broadway,Boulder, CO 80303) A rigorouscalculation of the noiselevel away from a broadband Recent measurementsof naturally occurringatmospheric sound sourceof knowncharacteristics under known meteorological conditions wavesnear I Hz indicatepotential uses for monitoringand studyinga requiresconsiderable computational effort. However, many practical varietyof geophysicalprocesses including avalanches, atmospheric tur- situationsfall into easilydescribed classes of meteorologicalcondition, bulence,severe weather, and earthquakes.A review presentstypical sourceand receiverheight, ground type, etc. Resultshave been of tab- signalcharacteristics including spectral content, showing clear differ- ulated full-waveacoustic calculations, systematically changing the encesbetween signals from varioussources. Possible generation mech- sourceand receiver configuration, frequency, and environmental param- anismsare discussedin the contextof thesedata and possiblepotential eters.The Lookupprogram accepts a one-thirdoctave source spectrum, practical usesindicated. sourceand receiver configuration, ground condition, and meteorological profile,then accesses the Lookuptable for the nearestcase and estimates the receiverspectrum. It doesthis in under I s on a PC. 9:15

SANS3. Flare noise damage potential. C. Moritz and R. Bruce 10:00 (Collaborationin Sci. and Technol., Inc., 15835 Park Ten PI., Ste. 105, Houston, TX 77084-5131) SANS& SoundProp--Fast,accurate prediction of soundpropagation under varying weather conditions and over hard or soft surfaces. Large elevatedrefinery flares producesignificant acoustic power PaulD. Sohoruerand Michael J. White (U.S. Army ConstructionEng. during periodsof heavyflaring. Much of this soundpower is low fre- Res. Labs.,P.O. Box 9005, Champaign,IL 61826-9005) quency, typically in the 4- through 16-Hz octave bands.The intense low-frequencysound can excite resonance frequencies in housesleading LOOKUP providesa fast, accuratecallable sub-routine to predict to noticeablevibrations of the walls.Through experimental investiga- the one-thir&octave band receivedsound spectrum for an arbitrary tions and publisheddata, correlationsbetween hydrocarbon and steam combinationof sourceheight, receiver height and range,one-third-

1872 J. Acoust.Soc. Am., Vol. 94, No.3, Pt.2, Sept.1993 126thMeeting: Acoustical Society of America 1872 octave-bandsource spectrum, and surfaceimpedance (soft or hard). 10:45 SoundPropis a shellthat facilitatesthe useof LOOKUP. With Sound- Prop,the user can accurately and quickly perform virtually any sound SANS9.Acoustic intensity measurements in the presenceof low Math propagationprediction for a softor hardsurface and a rangeof sound numberturbulent flow. Toby McNeal (Naval SurfaceWarfare Ctr., propagationconditions. Simple barriers can alsobe included.Future Acoust. Res. Detachment,Code 752, Bayview, ID 83803) and enhancementswill include separate specification of the source, path, and GeraldC. Lauchle (PennState Univ., State College, PA 16804) receiversurface impedance and additionalsound-speed profiles in the Acousticintensity measurements using the two-sensor cross-spectral LOOKUP library.SoundProp is limitedto simpleASCII text file out- densitytechnique are susceptible to errors when made in thepresence of putand must have a VGA monitor.Currently, SoundProp uses about 6 meanflow. These errors are predominantlydue to turbulentpressure MB of diskspace and must be locatedin driveC. WINSoundPropwill fluctuationsacting on and near the sensors.To quantifythese errors, be a Windowsversion of SoundPropand will be ableto plot graphical intensitymeasurements were performed in a soundfield that contained outputon any printersupported by Windows.These programs, devel- both an independentacoustic source and a mean, low Mach number opedby the U.S. Army ConstructionEngineering Research Laborato- (M<0.1), turbulentboundary-layer flow. The microphoneswere ries, are free. flushedmounted in the wall supportingthe turbulentboundary layer and the acousticsource was positioned a largedistance downstream. 10:15 The streamwisecomponent of intensitywas measured with and without the flow keepingthe soundoutput of the sourceconstant. Associated SANS7. Finite element and finite difference models for the fast-field biaserrors were calculated in accordancewith a theoreticallyestab- program in outdoor sound propagation. Kenneth E. Gilbert and lishedbias error [G. C. Lauchle,Noise Control Eng. J. 23, 52-59 ScottD. Hansen (Appl. Res.Lab. and the GraduateProgram in ( 1984)].As predictedtheoretically, the calculatedbias error decreases Acoust.,Penn State Univ., P.O. Box 30, StateCollege, PA 16804) rapidlyas the sensorseparation distance increases relative to the corre- The so-called"fast-field program" (FFP) hasbecome a popular lationlength associated with the turbulent boundary-layer pressure fluc- methodfor predictingsound pressure levels in outdoorsound propaga- tuations.[Work supported by various U.S. Navy projects at NSWCand tion. The methodrequires the solutionof a one-dimensionalGreen's ARL Penn Statc.] functionequation. The usualapproach in outdoorsound propagation hasbeen to obtainthe solution in termsof sinusoldsor specialfunctions. I1:00 Here, a simpledirect method is demonstratedthat useseither finite elementsor finitedifferences in muchthe sameway as doesthe para- 5aNS10. Active control of liquid-borneenergy in a pipe with a bolic equationmethod. The finite elementmethod presented here is uni-directional wave generator. Lisa Louie (Cardcrock Div., Naval adaptedfrom a range-dependentFFP modeldeveloped for underwater SurfaceWarfare Ctr., Carderock,Bethesda, MD 20084-5000) acoustics[K. E. Gilbert and R. B. Evans, in OceanSeismo-.4coustics, editedby T. Akal andJ. M. Berkson(Plenum, New York, 1986)].The Activeattenuation of narrow-bandsound in a liquid-filledsteel pipe finiteelement FFP hasbeen used successfully for propagationproblems wasconducted experimentally. The pipe is connectedto a noisesource in atmosphericacoustics for severalyears. The finite differenceap- at oneend and openedinto a largereservoir at the otherend. For active proach,which has been developed only recently,is morestraightfor- cancellationpurposes, a pair of flush-mountedactuators are locatedin ward than finiteelements but equallyaccurate. We comparethe FFP the mid-sectionof the pipe.The pair of actuatorsare usedto senda solutionsin termsof speedand accuracyusing several existing bench- uni-directionalwave that is equal in amplitudebut 180deg out of phase mark problemsas testcases. to thepropagating wave down the pipe. The consequence of implement- ingthis technique is that there is no increaseof energybetween the noise sourceand the actuators.Results are recordedby hydrophoneslocated 10:30 in many locationsalong the pipe and in the reservoir.Over 20-dB 5aNSS. Computation of turbulent boundary layer wall pressure reductionwas achieved. [Work supportedby ONR.] spectra. Dean Capone (Naval Surface Warfare Ctr., Acoust. Res.

Detachment,Code 752, Bayview,ID 83803) and Gerald C. Lauchle 11:15 (Penn StateUniv., StateCollege, PA 16804) 5aNSI1. Active noise control applied to extended sources in a The suitabilityof variouswave-vector-frequency spectral models for half-space.Steve Shepard and Kenneth A. Cunefare (The GeorgeW. predictingthe pointwall pressurespectrum due to developedturbulent WoodruffSchool of Mech. Eng., GeorgiaInst. of Technol.,Atlanta, GA boundary-layerflow overplanar, rigid surfacesis investigated.The in- 30332-0405 ) compressibleand compressiblemodels developed previously [D. Chase, J. SoundVib. 112, 125-147 (1987)] are givenparticular attention. The Recentwork adapted free-field boundary element method-based op- effectof finite-sizedmeasurement transducers is included in theintegra- timalactive noise control techniques for applicationin a half-spacewith tion of the theoreticalwave-vector-frequency spectrum over the in- a rigid or pressurerelease boundary. Here the requiredcontrol source planewave numbers in orderto arriveat an attenuatedpoint pressure strengthsand relativephases for activenoise control applied to a rect- frequencyspectrum that can be compareddirectly to existingexperi- angularsolid above a rigid planeare investigated.It is assumedthat one mentaldata [G. Schewe,J. Fluid Mech. 134, 311-328 (1983) (air), G. face of the solid is radiating harmonicallywith known surfacenormal C. Lauchle and M. A. Daniels, Phys. Fluids 30, 3019-3024 (1987) velocity.The existenceof uniquebehavior, as comparedto free-field (glycerineLand M.P. Horne and R. A. Handler, Exp. Fluids 12, conditions,for the controlsource strengths and achievablepower re- 136-139(1991) (water)]. The selectedexperiments cover a widerange ductiondue to the presenceof the planeis demonstrated.This unique of fluidproperties and Reynolds numbers: it is foundthat the optimum behavioroccurs at andnear certain discrete frequencies. These frequen- setof empiricalconstants needed to exercisethe Chase models depends ciesare not the characteristicfrequencies of the Helmholtzintegral for on the experimentconsidered. The need to considerviscous effects in the rectangularsolid; rather, they are relatedto the particularnoise futuremodeling is borneout whendealing with viscousfluids like glyc- sourcevelocity distribution and control source distribution. Finally, the erine. [Work supportedby variousU.S. Navy projectsat NSWC and half-spacecontrol formulation is employedto evaluatedata from an ARL Penn State.] experimentconducted in a hemi-aneehoicchamber.

1873 J. Acoust.Soc. Am., Vol. 94, No. 3, Pt. 2, Sept. 1993 126th Meeting:Acoustical Society of America 1873 FRIDAY MORNING, 8 OCTOBER 1993 SILVER ROOM, 8:00 A.M. TO 12:00 NOON

Session 5aPA

Physical Acoustics:Propagation and Nonlinear Acoustics

Charles E. Bradley, Chair BerkeleyCenter for Sensorsand Actuators,University of California,Berkeley, California 94720

ContributedPapers

8:00 comparingthe resultsof somesimplified cases to publishedresults of other numericalschemes and, wherethey are known, to analyticalso- SePAl. Dispersivepulse propagationand group velocity. Charles E. lutions.Specifically, results will be shownregarding the code'sability to Bradley (Appl. Res. Labs.,Univ. of Texas,Austin, TX 78713-8029) simulatethe 2-D linear propagationof a curvedshock wave front in a The propagationof pulsesin a dissipativemedium is investigated homogeneousmedium, and I-D nonlinearpropagation of pulseswith both theoreticallyand experimentally.The theoreticalwork is basedon dissipationand molecularrelaxation. Also presentedwill be somere- the dissipativedispersion integral, and the measurementsare madein an sults of 2-D nonlinearpropagation, in which an N wave with a curved air-filledperiodic waveguide (i.e., the dispersionis Bloch wave disper- wave front passesthrough a caustic.[Work supportedby NASA and sion). The dispersionintegral is consideredin the contextof a sequence the William E. Leonhard endowmentto the PennsylvaniaState Univer- of characteristicpulse duration distances. The pulsepropagates without sity.] distortionup to the smallestcharacteristic distance, and thereafterun- dergoesa new variety of distortionas it encounterseach subsequent 8:45 characteristicdistance. Several new solutionsof the dispersionintegral that exhibita varietyof novelpropagation properties are found. Pulses 5aPA4. Propagationof transient waves in a random medium. Alan that shift in frequencyas they propagate,accelerate as they propagate, R. Wenzel (NASA Langley Res. Ctr., MS 460, Hampton, VA andpropagate at near-infinitegroup velocity are foundanalytically and 23681-0001 ) verifiedexperimentally. [Work supportedby ONR.] A theoreticalanalysis of the propagationof transientscalar waves in a one-dimensionalrandom medium is presented.The indexof refraction 8:15 of the medium is assumedto deviateonly slightly from unity, which allows the analysisto be carried out with the aid of a perturbation $aPA2. Pulse.splitting in a nonlinear waveguide. Andrrs Larraza, method.The specificapproach adopted here combinesa renormaliza- William F. Coleman,and Anthony A. Archicy (Phys. Dept., Code tion techniquewith a travel-time-correctedaveraging procedure called PH/La, Naval PostgraduateSchool, Monterey, CA 93943) asynchronousensemble averaging. A generalexpression, valid for an A nonlineareffect in an acousticduct is describedfor waveguide arbitrary initial disturbance,is obtainedfor the variance of the wave. modesabove the first cutofffrequency, whereby a finite extentmodula- From that result,an expressionfor the varianceis derivedfor the special tion of the nonlinearmode splits into two disturbancesmoving with two casein which the initial disturbancehas the form of a ramp function differentvelocities of propagation.That is, for eachbit of information with arbitraryslope. These results show that the varianceof the waveis input, there will be two bits output. The effectwas first predictedby directly proportionalto the varianceof the refractiveindex of the me- Whitham for nonlineardispersive media [G. B. Whitham, Linear and dium, but is only weaklydependent on the propagationpath length.It Nonlinear Waves(Wiley-Intcrscience, New York, 1974)]. An experi- is alsofound that, asthe slopeof the rampfunction decreases, the wave ment to verify this phenomenonwill be discussed.The apparatuscon- variancedecreases as well. The presentationconcludes with someob- sistsof a 21-m-long,7-segment, thick-walled aluminum tube with a 2-in. servationson the relevanceof theseresults to the problemof sonic-boom internal diameter.Two high-intensitycompression drivers arranged in a propagationin the atmosphere.[Research supported by NASA.] push-pullconfiguration are mountedat one end to drive a modeabove the first cutoff frequency.A 3-m anechoictermination spanned the lengthof the last segmentat the other end. A physicalexplanation of 9:00 the effect,a simplifiedperturbative treatment of the problem,and pos- 5aPA5. Connection between structural and statistical models of sible applicationsto fiber optic communicationswill be presented. atmosphericturbulence. GeorgeH. Goedecke,Paul M. Pellegrino [Work supportedby ONR and NPS Direct-FundingProgram.] (Dept. of Phys.,NMSU, Las Cruces,NM 88003-0001),and Harry J. Auvermann (Army Res. Lab., BatfiefieldEnvironment Directorate, 8:30 WSMR, NM 88002-5501)

5aPA3. A multidimensional numerical algorithm to simulate the A structuralmodel of isotropichomogeneous atmospheric turbu- propagation of a shock wave through caustics. Andrew A. Piacsck lence is presented, in which the turbulence is described as an ensemble (Graduate Program in Acoust., Penn State Univ., P.O. Box 30, State of individual localizedquasistatic eddies or turbules.Turbules of differ- College, PA 16804) ent sizesa are assumedself-similar with respectto their temperature and flow velocityfields, and randomly positionedand orientedwith no One strategyin tbe effortto explainfeatures of observedsonic boom correlations.It is shownthat, in order to obtain agreementwith the profilesthat deviatefrom the classicalN shapeis to simulate,one a Kolmogorovacoustical scattering spectrum, the usualrelation between computer,the propagationof shockwaves in an inhomogeneousme- turbuleflow speed v andsize, v •x a I/3, must be assumed, and, in addi- dium. A time-marchingfinite-difference code is beingdeveloped by the tion,(i) turbulenumber densities must be proportional to a-3, and(ii) author which employsa multidimensionalexplicit flux correctedtrans- turbulesizes must be in a geometricsequence, from the outer scaleto port scheme,based on work by Zalesak [1. Comp. Phys. 31, 335-362 the inner.It is alsoshown that the Kolmogorovspectrum is insensitive (1979)] and McDonald (NPE sourcecode and private communica- to theturbule morphology, and that the extent of the"inertial range" is tion). Certainessential features of the programhave been examined by influencedonly weakly by themorphology. Expressions for C• andC•,

1874 J. Acoust.Soc. Am., VoL 94, No. 3, Pt. 2, Sept. 1993 126thMeeting: Acoustical Society of America 1874 andfor the boundaries of the inertial range, are derived in termsof the approximationsit reproducesDaigle's results for homogeneousatmo- structuralparameters. spheresand compareswell with the upwardrefraction measurement of Parkin and Scholesand with measurementstaken undera varietyof

9:15 refractiveconditions at Bondville,Illinois by the U.S. Army Construe- tion EngineeringResearch Laboratory. 5aPA6. Comparisons of experimental measurementsof sound propagationover a hill and the polar parabolic equation method. ChulssoYou, Henry E. Bass (Natl. Ctr. for Phys.Acoust., Univ. of 10:00 Mississippi,University, MS 38677), and KennethE. Gilbert (Penn $aPA9. Examination of sonic boom propagationthrough turbulence StateUniv., StateCollege, PA 16804) with ray theory. Leick Robinson (Appl. Res.Labs., Univ. of Texas, The polar parabolicequation (POPE) method,which introduces Austin, TX 78713-8029) the boundaryfitting coordinates into the parabolicequation (PE) The propertiesof sonicboom propagation through turbulence con- method,was developed to solvefor soundpropagation over a curved tinueto be exploredby a ray theoryapproach. Ray theoryis usedto surfaceand over irregular terrain (hills) [X. Diet al., J. Acoust.Soc. modelthe effects of refractionand subsequent folding of the wavefront Am. 92, 2431 (A) (1992)]. POPEcan include realistic sound-speed by an instantaneousrealization of the turbulence.Comparison is made profilesand ground impedance. Predictions based upon the POPEhave with otherprediction methods. These results are comparedwith char- beencompared to measurementsat the JAPE 91 (JointAcoustic Prop- acteristics observed in sonic boom measurements. The relative contri- agationExperiment) terrain masking experiment at White SandsMis- butionsof the large and small scale modesof the turbulent field are sileRange, New Mexicoduring the period27-28 July 1991.The sound evaluated. sourceswere hovering helicopters at the baseof a hill and far awayfrom the hill. In theJAPE data,the relativesound pressure level decreases rapidlyfrom the top of thehill andbecomes nearly constant along the 10:15 baseof thehill. Thischaracteristic feature is well predicted by thepolar parabolicequation calculations. POPE methodappears to be an accu- 5aPA10. Comparison of measured and predicted pure tone rate meansfor predictingsound propagation over realisticterrain. propagationlevels from JAPE-l: An evaluationof the performanceof ASOPRAT. Carl K. Frederickson,Henry E. Bass,Richard Rasper, and JohnMesser (Phys.Acoust. Res. Group, Univ. of Mississippi, 9:30 University,MS 38677)

5aPA7. Determinationof turbulent velocity correlationsby the Shortgrangepropagation data (<2 km) from the Joint Acoustic nonlinearscattering of crossedultrasonic beams. Murray S. Korman PropagationExperiment Phase One (JAPE-I) has beenused to evalu- and JamesE. Parker,III (Dept. of Phys.,USNA, Annapolis,MD ate the performanceof the advancedsound propagation in the atmo- 21402) sphere(ASOPRAT) computercode. Speakers mounted 2 and 30 .m abovethe groundwere used as puretone sources for the short-range The nonlinearinteraction of two, mutuallyperpendicular crossed measurements. Pressure levels measured in the time domain have been ultrasonicbeams, overlapping in thepresence of turbulence,generates a Fourieranalyzed to produceplots of the pressuredue to a particular scatteredsum frequency component that radiatesoutside the interaction frequencyover time. Meteorological profiles measured at the experi- region.In the absenceof turbulence,virtually no scatteredsum fre- ment site wcrc usedas input for the predictionroutine ASOPRAT. quencycomponent exists (outside the interaction region). A theoretical Agreementbetween the predictedand measuredpropagation losses is investigationis reportedthat relatesthe shapeof the ensembledaver- very good.Source strength data werenot availableas of the writingof agedscattered sum frequencyintensity spectrum, I+ (o, 0.) (which thisabstract, so at thistime comparisonsare all relativeto a reference exhibitsa Dopplershift, frequency broadening, skewness, and kurtosis), microphoneat the ground.Source strength data may be availableby the to the scatteringangle 0., incidentand scatteredwave vectors(where time of the meeting. K+ = ks-- [k• +k2]), and statisticalproperties of the turbulentvelocity field v. The n spectralmoments ((K+.v)")crfI+(o•,O.) - (co))• do (obtainedfrom experiment)are usedto evaluateturbulent 10:30 velocitycorrelations like (oxoy),where n=2. Thescattering geometry involvesrotating the axisof the transmittingcrossed beams (which are SaPAll. Comparisonbetween short-term and long-termaverages of alwaysperpendicular to eachother) in the planecontaining the sub- turbulence parametersfor use in atmosphericacoustics. John M. mergedcircular water jet and receiveraxes. Angle 0, is measured Noble (U.S. Army Res. Lab., BattlefieldEnvironment Directorate, tweenthe ray bisectingthe transmitting axes and the stationary receiver ATTN: AMSRL-BE-M, WhiteSands Missle Range, NM 88002) axis.The crossedbeams are focusedand overlapat the commonfocal Sonicanemometers are good instruments for measuringtemperature point. Spectralmoments, obtained from scanningthe overlapregion and wind speedfast enoughto calculatethe temperatureand wind acrossthe jet, are usedto predictvelocity correlations across the width structureparameters used to calculatethe variancein the acousticindex of thejet with goodspatial resolution. of refraction.The problemis howlong of an averageis needed to obtain a representativevalue of the strengthof the turbulencefield in the 9:45 atmosphere.In additionto this problem,there are severalproblems associatedwith makingpoint measurements and usingthem to repre- 5sPA8. Calculation of average turbulence effects on sound senta turbulencefield. These problems will be examinedby analyzing propagation based on a fast field program formulation. Richard someof the sonicanemometer data from the JointAcoustic Propaga- Raspet and Wenliang Wu (Univ. of Mississippi,University, MS tion Experiment(JAPE) conductedduring July 1991at DIRT site 38677) locatedat White SandsMissle Range, New Mexico.This experiment Daiglehas published a seriesof papersin whichhe hasapplied the providesturbulence data from sonicanemometers at five heightsfor turbulent scatteringtheories of Chernov and Karavainikov to sound severalhours a day overa periodof approximately2 weeks. propagationover hard and finite impedancegrounds. In thesepapers, Daiglehas introduced the decorrelationin phaseand amplitudedue to 10:45 turbulence along the direct and reflected path into the spherical wave reflectionanalysis for a nonrefractingatmosphere. The phaseand am- 5aPA12. Application of the CFFP to sound propagation in plitudedecorrelation terms have been incorporated into the evaluation inhomogenemm media above a ground with an impedance of the spectralintegral of a fast field programfor propagationin a discontinuity.Y.L. Li andMichael J. White (US Army Construction refractingatmosphere. Although the calculationinvolves two significant Eng. Res.Lab., P.O. Box 9005, Champaign,IL 61826-9005)

1875 J. Acoust.Soc. Am., Vol. 94, No. 3, Pt. 2, Sept. 1993 126thMeeting: Acoustical Society of America 1875 Using the chirp fast field program (CFFP), a systematicmethod has Makin, and Mark F. Hamilton (Dept. of Mech. Eng., Univ. of Texas, beendeveloped for numericalcomputation of soundpropagation in an Austin, TX 78712-1063) inhomogeneousatmosphere above a groundwith an abruptchange in impedance.In situationswhere a noiseis generatedabove one type of The reflectionof focused,finite amplitude sound beams from curved groundsurface (say pavement)and travelsbeyond its edge,onto a targetsin water wasinvestigated experimentally and theoretically.Mea- secondtype of surface(e.g., grassyground), eachsurface usually con- trols the rate of attenuationnear it. When the air near the ground is surementsof small signaldiffraction effects were usedto characterize refractive,it may emphasizethe attenuationduring downward refrac- the effectiveradius ( 1.9cm) andfocal length ( 15 cm) of the source,the tion and eliminateit in upwardrefraction. Other effectsof the inhomo- centerfrequency of whichis 2.25 MHz. Detailedcomparisons are made geneousatmosphere are discussed.Several interesting examples will be betweenmeasurements of harmonicgeneration in the incidentfocused presented. beamand numericalresults from a computercode that solvesthe KZK equationin the frequencydomain [Naze Tjotta et al., J. Acoust. Soc. 11:00 Am. 89, 1017-1027 (1991)]. Reflectionfrom both convexand concave target surfacesis considered.The targetsare made of nickel with dif- 5nPA13. Low-frequency wind noise for a microphone inside a ferent radii of curvature down to a minimum of 5 cm. Measurements of spherical foam windscreen. Scott Morgan (Dept. of Phys., the reflectedbeam were obtainedwith a membranehydrophone that Southeastern Louisiana Univ., 878 SLU, Hammond, LA 70402) and Richard Raspet (Univ. of Mississippi,University, MS 38677) wasplaced between the sourceand the target.Theoretical predictions for harmonicgeneration in the reflectedfield wereobtained by modify- Windscreensare commonly used to reduce wind noise in outdoor ing the computercode to accountfor the phaseshifts introducedby measurementsby shieldingthe microphonefrom the incomingflow. In interactionof the incidentbeam with the target.Theory and experiment this papera theoreticalmodel for wind noisereduction of a spherical are in goodagreement for both the incidentand reflectedbeams. [Work foam windscreenand experimentalevidence supporting this modelare supportedby the Packard Foundation and the Office of Naval Re- presented.Results show that wind noise reductionis approximately search.] independentof windscreendiameter for turbulencescale sizes that are much larger than the windscreenand that wind noisereduction scales well with the screen number (defined as the ratio of the windscreen diameter to the scale size of the turbulent eddies) for screen number 11:45 valuesless than one. Calculationsusing averagewindscreen surface pressuremeasurements yield wind noisereductions that are of the same 5aPAI6. Measurementsof finite amplitudepulses radiated by plane order of magnitudeas thosemeasured. circular pistons in water. Michalakis A. Averkiou and Mark F. Hamilton (Dept. of Mech. Eng., Univ. of Texas, Austin, TX 11:15 78712-1063) 5a_PAI4. Sound propagationin inhomogeneousmedia above a ground with a barrier. Y. L. Li and Michael J. White (U.S. Army Measurementsare reportedfor finite amplitudeacoustic pulses ra- Construction Eng. Res. Lab., P.O. Box 9005, Champaign, IL diatedby planecircular pistons in water.Pulses with centerfrequencies 61826-9005 ) of severalmegahertz, peak soundpressures up to 1 MPa, durations To studythe problemof scatteringof acousticwaves from a ground rangingfrom approximately2 to 20 cycles,and differentamplitude and with a barrier,the exactexpression of the Green'sfunction due to a line frequencymodulations were investigated. Measurements of shortpulses sourceembedded in a layeredmedium has beensuccessfully incorpo- weremade very near the source,where the centerwave and edge wave rated into the Helmholtz-Kirchhoffintegral equation. An extensionof can be separated.Pulse envelopedistortion that accompaniesshock the method of moments,which can solvethe Helmholtz-Kirchhoff in- formationin frequency-modulatedtone bursts is demonstrated.Acous- tegral equationfor studyingthe problem of sound scatteringin the tic saturationof pulsedsound beams is alsoinvestigated. All measure- inhomogeneousmedium has beendeveloped. Using the method,the mentsare comparedwith theoreticalpredictions obtained from a com- effectsof scatteringin the regionbeyond a barrier are studiedfor situ- puter codethat solvesthe KZK equationin the time domain[Lee and ationswhen the backgroundmedium is inhomogeneous.The effectsof Hamilton, UltrasonicsInternational 91 ConferenceProceedings the inhomogeneousatmosphere are discussed.Several interesting exam- pieswill be presented. (Butterworth-Heinemann,Oxford, 1991), pp. 177-180]. Very good agreementbetween theory and experimentis obtainedboth in the near field and the far field, on and off axis. Artifacts in measurements of 11:30 waveformscontaining shocks, which are attributed to bandwidth limi- 5aPA15. Measurementsof focused,finite amplitude sound beams tationsof membranehydrophones, are discussed.[Work supportedby reflectedfrom curvedtargets. MichalakisA. Averkiou,Inder Raj S. the PackardFoundation and the Officeof Naval Research.]

1876 J. Acoust.Soc. Am., Vol. 94, No. 3, Pt. 2, Sept.1993 126thMeeting: Acoustical Society of America 1876 FRIDAY MORNING, 8 OCTOBER 1993 CENTURY-SPRUCE ROOM, 8:30 A.M. TO 11:45 P.M.

Session $aSA

Structural Acousticsand Vibration: Radiation and Scattering Measurements

Geoffrey L. Main, Chair Officeof Naval Research,800 North QuincyStreet, drlington, Virginia22217

ContributedPapers

8:30 and Yves H. Berthelot (Georgia Inst. of Technol., Atlanta, GA 30332-0405 ) $aSA1. Energy branchingof a subsonicflexural wave on a plate at an air-water interface: Transition radiation and the acoustic wave field Experimentshave been conducted on the thermaelasticgeneration in water. ThomasJ. Matula and Philip L. Marston (Dept. of Phys., of Lamb wavesin platesby a Q-switchedruby laser. Detectionwas WashingtonState Univ., Pullman, WA 99164-2814) performedboth by interferometriclaser probe and a miniaturepiezo- electricpinducer. The long-termobjective of this work is to determine The diffractionof subsonicflexural plate waves due to a discontinu- variouscharacteristics of the plate suchas materialproperties, plate ity in fluid-loadingis experimentallyinvestigated. A toneburst of flex- thickness,flaws, and inhomogeneities,or even bonding between plates ural wavespropagates down a plate, the lower sectionof which is sub- by comparingexperimentally determined points with the theoretical mergedin water.Observations indicate that thereoccurs a branchingof dispersioncurves. The techniqueconsists in formingon the surfaceof energyas the flexuralwave passesthrough the air-water interface.A the specimenan arrayof confocalarc sourcesby passingthe laserbeam portionof the energycontinues along the plate as a subsonicflexural througha Fresnellens. The array spacingproduces a "forcingwave- wave with an associated evanescent wave. A second acoustic wave length"for which only a few specificfrequencies can propagate.Dis- (which is termedtransition radiation) originatesat or near wherethe persiancurves can be obtainedby measuringthe frequencycontent of plate crossesthe interface,and propagatesin water to the far field. In the receivedsignals for a range of wave numbers.Because of the the near field of the interface there exists an interference between the narrow-bandnature of the technique,and becauseof the confocalge- two acousticwaves in waterthat resultsin a seriesof pressurenulls. The ometryof the sourcedistribution, this techniqueoffers a relativelyhigh pressurenulls are associated with a •r phasechange in thewave field and signal-to-noiseratio. Good agreementis obtainedbetween theoretical are indicatorsof wave front dislocations[P. L. Marston, "Geometrical and experimentaldispersion curves especially for the lowermodes, thus andCatastrophe Optics Methods in Scattering,"Physieal.•coustics (Ac- showingthat the proposedtechnique has potentialfor the above- ademic,New York, 1992), Vol. 21, pp. 1-234]. A computationof the mentionedapplications. [Work supportedby the National Science wave field in an unbounded fluid due to a line-moment excitation of a Foundation.] plate is comparablewith the null pattern observedbut differsin certain details.[Work supportedby ONR.] 9:15

8:45 5aSA4. Impulse responsefor backscatteringby a thin spherical shell: Measurement and wave interpretation. Gregory Kaduchak, $aSA2. Repulsion of phase-velocitydispersion curves and the nature ChristopherS. Kwiatkowski,and Philip L. Marston (Dept. of Phys., of plate vibrations. B. Hosten,M. Deschamps,A. Girard (Lab. de WashingtonState Univ., Pullman, WA 99164-2814) M6can. Phys., Univ. BordeauxI, F-33405 Taleace, France), and H. •berall (UniversityBordeaux I and CatholicUniv. of America, A broadbandsheet source was developedto producea pressure impulsewith a planarwave front containinga widerange of frequency Washington,DC 20064) components[C. S. Kwiatkowskiet al., to be presentedat thismeeting]. The Lamb wavespropagating in an elasticplate in •acuo generate This sourceis nearlyacoustically transparent and was usedfor back- compressional(L) and sheartype (T) platevibrations that are coupled scatteringfrom an emptystainless steel spherical shell where prominent due to the boundaryconditions. Without suchcoupling, their phase- featuresin the shell'scalculated impulse response are observedover a velocitydispersion curves would form two intersectingfamilies, which wide frequencyinterval. A widebandhydrophone was placed in the far at high frequencytend towards the elastic-wavespeeds C L and Cr, field of the scattereron the oppositeside of the source.Time records respectively.It is shown that the coupling causesa repulsionof the reveal a gaussianwave packet associatedwith the excitationof the dispersioncurves, similar to that encounteredin atomicphysics for the subsonica o_ wave responsiblefor a large backscatteringenhancement energylevels of atoms combininginto molecules,which preventstheir near the coincidencefrequency. Superposed on the same recordsare intersectionand at the sametime exchangesthe nature (L•-•T) of the large contributionsfrom the low frequencyexcitation of the underlyingvibrations. However, in the repulsionregions a successionof mode[G. Kaduchakand P. L. Marston,J. Acoust.Soc. Am. 93, 2700- dispersioncurves combines to asymptoticallyapproach the uncoupledL 2706 ( 1993)]. The shellused in the experimenthas a thicknessto radius or T dispersioncurves, respectively. For the caseof a platebounded by ratio of 2% for which the abovescattering phenomena occur for fre- fluid on one side,and vacuumon the other, the dispersioncurves of the quenciesless than 450 kHz. [Work supportedby ONR.] fluid-borne (Stoneley-Scholtetype) wave, which is known from the studiesof Grabovskaand Talmant to be presentin this case,and of the 9:30 usual.40 Lamb waveexhibit a similarrepulsion phenomenon. 5aSAS. Observation of the prompt high-frequency enhancementof tone bur•tg baekgeattered by a thin •pherieal •hall near the firgt 9:00 longitudinal resonance. Gregory Kaduchak and Philip L. Marston (Dept. of Phys., WashingtonState Univ., Pullman, WA 99164-2814) 5aSA3. Fresnel array method for determiningthe dispersioncurves in plates. R. Daniel Costley,Jr. (Naval Res. Lab., UnderwaterSound A prominentfeature predicted for the backscatteringof tone bursts ReferenceDetachment, P. O. Box 568337, Orlando, FL 32856-8337) by thin sphericalshells is an enhancementof a guidedwave contribution

1877 J. Acoust. Soc. Am., Vol. 94, No. 3, Pt. 2, Sept. 1993 126th Meeting: AcousticalSociety of America 1877 near the first longitudinalresonance. This has beenexplained with a Thesetwo fieldsare decomposedin the wave-vectordomain in order to backwardray model of a leaky Lamb wave whereenergy is leakedoff extractthe scatteredfield. Numerical simulations are performedand the withouthaving circumnavigated the backside of the shell[P. L. Mar- effectof variousparameters is investigated.Specifically, the distance stonet a!., J. Acoust.Soc. Am. 90, 2341 (1991); D. H. Hughes,Ph.D. betweenthe two-holographycylinder, the samplingrate, and the aper- thesis,Washington State University (1992)]. The relevants2b Lamb ture sizeare investigatedin the fieldseparation technique. In addition, wavehas opposinggroup and phasevelocities giving rise to prompt experimentalstudies were conducted inside an aneehoicchamber with a radiationfollowing the directspecular echo. The presentresearch gives baffledloudspeaker as a sourceand a cylinderas a scatterer.The de- a comparisonbetween a ray theoryapproximation and experiments in composedscattered field is then used to estimatethe far-field target whichtone bursts having carrier frequencies in the range595 < ka < 640 strength.The near-fieldscattering is alsoinvestigated. were incident on an empty stainlesssteel sphericalshell in water of radiusa= 12.7 cm. The sphere'sthickness to radiusratio is 2%. The 10.'45 responsegenerally follows the predictedamplitude which can be close to 4.5 timesthe specularamplitude. [Work supported by ONR.] 5aSA9. Comparisonof dual surface and tri-surface approachesfor acousticalholography measurements of radiated and scatteredfields. Michael A. Sartori and JosephA. Clark (CardcrockDiv., Naval Surface Warfare Ctr., Bethesda, MD 20084-5000) 5aSA6. The influence of internal structures on historic scatter from finite cylindricalshells near axial incidence.Matthew Conti and Ira Usingnear-field measurements of the pressurefield of an immersed Dyer (Dept. of OceanEng., MIT, Cambridge,MA 02139) structure,an estimateof the strncture'sradiated field and scatteredfield can be made.With the pressureand the pressuregradient measured at Previousresults have examinedthe scatterfor an empty shell at discrete locations in the near field, a discretized solution of the exterior axial incidenceillustrating the primary role of the endcap.Building on Helmholtz integral is solvedto obtain the far-field pressure.This ap- this,important differences in the bistaticscatter due to the presenceof proachhas been shown to work for bothacoustic radiation and acoustic internalstructures are presented.In addition,differences due to source scatteringproblems. Using two normal surfacesto approximatethe incidenceaway from axial are investigated.Discussion is basedupon pressuregradient, parametric simulations were performed to determine bistaticmeasurements on an emptyshell with endcaps,a duplicateshell the scatteredfield predictabilityof the approachfor an insonifiedrigid with internalring stiflehersand a duplicatering stiflenedshell with sphere.The resultsindicate that this dual surfaceapproach better pre- resilientlymounted wave-bearing internal structures. Integrated target dictsthe scatteredfield when the surfacesare very close,which implies strengthsshown as a functionof observationangle reveal spatial regions that a goodapproximation of the gradientis needed.A differentap- where the internal structurescause significant change. Of particular proximationof the pressuregradient uses three surfaces instead of two. interestis enhancementof targetstrength near backscatter. In conjunc- Usinga cylindricalshaped measurement surface, the radiatedpressure tion with conventionalbeamforming techniques, these analyses reveal field from a monopoleand the scatteredpressure field from a rigid the distributionof energyalong the shalllength. This distributionis sphereare simulatedfor the differentcases of the approximatedgradi- modifiedby rotationof incidenceaway from axial. Relativedecay rates ent, namelythe dual surfaceapproach and the tri-surfaceapproach. The and frequency-dependenteffects are also discussed.The bistaticmea- effectson the predictabilityof the radiated field and the scatteredfield surementswere conducted over a frequencyrange of 2.5 < ka < 10,cor- are discussed.[Work supportedby ONR.] respondingto 3/4 to 3 timesthe ring frequencyof the shells.[The authorsacknowledge the assistanceof NRL for acquisitionof data. 11:00 Work supportedby ONR.] 5aSAI0. Wave vector measurementsof empirical design transfer functions. JosephA. Clark and Michael A. Sartori (CardcrockDiv., Naval Surface Warfare Ctr., Bethesda,MD 20084-5000) 5aSA7. Experimentalinvestigation of nonspecularscattering from a framed shell. Brian H. Houston,Joseph A. Buearo,and DouglasM. Empiricaldesign transfer functions can be usedto predictthe radi- Photiadis (Phys. Acoust.Branch, Naval Res. Lab., 4355 Overlook ated noisegenerated from variouscomponents in a system.The Darby Ave., Washington,DC 20375) methodis one exampleof an approachused to find theseempirical designtransfer functions.For an immersedand radiating structure, Recentlythe existenceof flexuralBloch waves contributing signifi- near-fieldmeasurements of the pressurefield can be wavevector filtered cantly to featuresobserved in far-fieldexperimental data was reported to find the empirical designtransfer function from the structural input [Photiadiset aL, J. Acoust.Soc. Am. 93, 2413(A) (1993)]. In this point to the acousticfar field.Assuming a cylindricalbody excitedby a previouswork, broadbandscattering data from framedand unframed forceand radiating,a discreteline array of pressuresensing devices are low aspectratio fluid-loadedshells (!/a = 3) werestudied. Calculations usedto measurethe near-fieldpressure. The acousticpressure data of the dispersioncurves for an infiniteribbed shell were usedto predict measuredat eachpoint are sampled,digitized, time averaged,and fre- the locationsof the peaksin the backscatteredcross section. Here, the quencytransformed. The position-frequencydomain pressureis then resultsof the scatteringfrom a high aspectratio (i/a=8} pseudoperi- transformed into the wave vector domain, and the far-field radiation is odicallyframed shell are reported.The variouselastic wave types using predicted.The empiricaldesign transfer function is foundby dividing the infiniteframed shell dispersion relations are identifiedand the rele- the predictedfar-field radiation by the input force. The mathematical vant contributionsare quantified. developmentof this approachis presented.Silrlulationa Ere presented for variousradiation sources, including a monopoleand a discreteline 10:15-10:30 Break source.The pressurepredictions of the wavevector are comparedwith the pressuredirectly computedfor the sources.[Work supportedby ONR.] 10:30

5aSAS. Scattering investigationwith cylindrical acousticholography. 11:15 Ming-To Chengand J. Adin Mann III (Dept. of Aerosp.Eng. and Eng. Mech., Iowa StateUniv., Ames,IA 50010) 5aSAII. Nature of the Scholte wave on a cylindrical shell. G. Maze, F. L6on, L Ripache (LAUE, Univ. Le Havre, 76610 Le Havre, The objectiveof this paper is to investigatesound scattering of a France),and H. 0berall (Univ. of Le Havreand Catholic Univ. of rigid scatterer using a two-plane cylindrical acoustic holography America, Washington, DC 20064) method. A piston source,which is vibrating sinusoidally,illuminates a scatterer.The superimposedincident and scatteredfields are measured The real parts of the eigenfrequenciesof an evacuated, fluid- in the near field of the scatterer using cylindrical acousticholography. immersedinfinite cylindrical shell can be usedto obtainthe dispersion

1878 J. Acoust.Soc. Am., VoL 94, No. 3, Pt. 2, Sept. 1993 126th Meeting:Acoustical Society of America 1878 curvesversus frequency of the phasevelocities of familiesof circumfer- The experimentalmeasurements of high-order mechanicalreso- ential waves.These wavesare analogousto thoseof the familiesof nancesof metallicstructures in the high-frequencydomain is generally Lamb waveson an elasticplate in vacuo,but containan additional.4 difficult and unreliable,due to the methodsof excitationsand analysis. wave correspondingto the Scholte-Stoneleywave in the fluid loading Here, an originaltechnique associating a nondestructive •er•ussive ex- [seeM. Talmant, Ph.D. thesis,Univ. of Paris VII (1987), or M. Tal- citationtogether with an acousticdetermination of the near field created inant et al., J. Acoust.Sac. Am. 86, 278 (1989)], which is approxi- by the vibrationsof the structurein air are proposed.The excitationis matedby the first Franz wave lB. Clotteauet al., J. Acoust.3, 213 obtainedusing a steelball magneticallyactivated, which createsa cali- (1990)]. Near the coincidencefrequency, a repulsionphenomenon is brated impulse.The observationis made usinga large bandwidth mi- obtainedbetween the (Lamb wave) .40 and the ,4-wavedispersion crophone.The experimentationshave been carried out on "gongs"(alu- curves,analogous to that in perturbed,quasidegenerate atomic levels. minum platesof l-ram thicknesswith other dimensionsof the order of An analyticexplanation is provided,using perturbation theory, for the the meter) possessingnoncanonical shape (stadium, sarcophagus...). form of the dispersioncurves and the natureof the correspondingwaves With this high signal-to-noiseratio obtainedin an anecho¾croom, it is in the regionof repulsion. possibleto obtainseveral hundred eigenfrequencies witha resolutionof the order or better than 1/10th the differencebetween neighboring fre- 11:30 quencies.This wasattained without any particulartreatment other than the spectralLMS analysis.The signaldynamics is around 80 dB, which 5aSA12. New methodof investigationof large bandwidthresponse of allowsone to obtain the pole and zerosof the transferfunction, imply- mechanicalstructures. M. Lagier,G. Vanderborck (ThomsonSintra ing that the amountof informationthus obtainedis considerable.The ASM, 525, Routedes Dolines, BPI57, 06903 SophiaAntipolls Cedex, resultswere then comparedwith thosepredicted within the theoretical France), F, Mortessagne,O. Legrand,and D. Sornette (CNRS URA frameworkproposed previously, in terms of quantumchaos methods 190, Facult6 des Sciences,06108 Nice Cedex 02, France and X-RS, appliedto high-frequencyvibrations of structures,in order to charac- Parc-Club,91893 Orsay Cedex,France) terizethe natureof the spectrumand the vibrationeigenfunctions.

FRIDAY MORNING, 8 OCTOBER 1993 LOWER PLAZA, 8:00 A.M. TO 12:00 NOON

Session 5aSP

SpeechCommunication: Topics in SpeechCommunication Research (Poster Session)

James R. Sawusch, Chair Departmentof Psychology,Park Hall, State Universityof New York at Buffalo,Buffalo, New York 14260

ContributedPapers All posterswill be on display from 8:00 a.m. to 12:00 noon. To allow contributorsan opportunityto see other posters, contributorsof odd-numberedposters will be at their postersfrom 8:00to 10:00a.m. and contributorsof even-numberedposters will be at their postersfrom 10:00a.m. to 12:00noon.

5aSP1. Acoustic and syntactic correlates of hesitations in In the work by Sussmanet al. [J. Acoust.Sac. Am. 90, 1309-1325 spontaneoussla•eeh. Nanette Veilleux, Ahwat Schlosser,and Mari (1991)], locusequations, which describelinear relationshipsbetween Ostendorf(ECS Dept., Boston Univ., 44 CummingtonSt., Boston, the onsetand steady-stateformant values in consonant-vowelsyllables, MA 02215) have beenexperimentally tested using a large quantity of acousticdata and beenproposed as a sourceof relationalinvariance for stop place One of the difficultiesin modeling the prosody of spontaneous categorization.In this presentation,a statisticalmodel is presented, speechis distinguishinghesitations from fluent intonational phrase which utilizesthe conceptualizationof the locusequations as a basisfor breaks.The goal of this study is to identify acousticand syntacticcues parametricmodeling of phoneticcontexts•plaee of articulation,and of that canbe usedto bettermbdel hesitation phenomena. The studyis their acousticconsequences--formant transitions. The model is based basedon a setof severalhundred utterances of spontaneousspeech from on hidden Markov model representationof formant-transmissionmi- the ATIS corpus,each with prosodicconstituents and hesitationsla- crosegmentsof speech.A generalizedexpectation-maximization algo- beledby hand and syntacticconstituents and phoneticalignments la- rithm is developedfor automaticestimation of the model parameters. beledautomatically. The first set of analysescompared acoustic corre- The proposedmodel is capableof generalizingconsonant characteristics latesfor prosadiephrase boundaries with and withouthesitations. For from a smalltraining data setwhere the contextualinformation is only constituentsbelow the level of the intermediatephrase, the average sparselyrepresented, and is henceapplicable to very largevocabulary durationof a pauseis longerwhen there is a hesitation(mean 270 msvs speechrecognition problems. Results from vowel classificationexperi- 19 ms), as is the meannormalized segment duration in the word-final ments(TIMIT database),demonstrating relative performance between syllablerhyme (mean 1.8 vs 0.2), both with significance p < 10 -5. The this locus-basedmodel and the conventionalhidden Markov model, will secondset of analyseslooked at the differencesin syntacticstructure at be presented. word boundarieswith and without hesitations.Again, for constituents gaSP3. The phonologlcal reality of locus equations across manner belowthe level of the intermediatephrase, results show that hesitations class distinctions: Preliminary observations. Harvey M. Sussman are likely to occur after a conjunction,auxiliary verb, or preposition, (Depts. of Linguist. & SpeechCommun., Univ. of Texas, Austin, TX i.e., at locationswhere the entropyof next-wordcandidates is relatively 78712) high. Locusequations, regression fits to coordinatesobtained by plotting 5aSP2. Vowel clusaification using a microsegmental model for F2 of a variety of vowelsat their midvowelnuclei in relation to F2 at formant transitionbased on locusequations. L. Deng and D. Braam the acousticonset of the CV syllablehave been shownto phonetically (Dept. of Elec. and Camput.Eng., Univ. Waterloo,ON N2L 3GI, indexplace of articulationwithin oral stopcategories across speakers of Canada) diverselanguages-English, Swedish, Cairene Arabic, Thai, and Urdu.

1879 J. Acoust. Soc. Am., Vol. 94, No. 3, Pt. 2, Sept. 1993 126th Meeting: Acoustical Society of America 1879 The purposeof this studywas to determineif locusequations best songof the zebrafinch consists of simultaneousand sequentialarrange- encode featural or segmentalentities. Several consonantalmanner mentsof acousticelements. Neuronal responses to individualsong ele- classeswere assessed.The inventory consistedof CVt tokens having mentsand to syllablescomposed of harmonicfrequencies were studied initial approximants---/w/,/j/,/r/,/1/; fricatives•/v/,/•l/,/z/,/3/; in each subdivisionof field L and HVc. The responsesto pairwisese- nasaism/m/,/n/. In addition voicingcontrasts were examinedusing quencesor harmonic syllablesdiffered from their responsesto an indi- voicelessstops (s/Cl/VC 2) with C•=/p/,/t/,/k/. Ten roedialvowel vidual element or a tone presentedin isolation. These nonlinear re- contextswere used.Locus equations were found to acousticallydistin- sponseswere evaluatedby a mattix-basedanalysis method. Results guishplace contrasts within each manner class, with nasalityand voic- showeda hierarchicalincrease of nonlinearinteractions as a recording ing not affectingthe place feature. However, similar place features site moved from field L to HVc. Both sequentialand simultaneous acrossstop-fricative--approximant classes, did not correspondin terms nonlinear interactions were enhanced from field L to HV½. These inter- of slopeand y-interceptvalues. It wasconcluded that locusequations actionsinvolved either inhibitory or facilitatoryeffects. Although, in bestcharacterize segment-based rather than feature-based,entities. theory,this selectivitycould be formedby a linear way, the songselec- tivity provedto be achieveddominantly by thesenonlinear interactions. $aSP4. Effectsof speakingrate, focal stress,and sentenceposition on [Work supportedby IHFSPO.] spectral characteristicsand vowel duration. Dawn M. Behne (Linguist.Inst., Univ. of Trendhelm,N-7055 Dragveil,Norway) and 5aSP7. Relative perceptual prominence of fundamental frequency LynneC. Nygaard (Indiana Univ., Bloomington,IN 47405) peaksin the presenceof declination. BrunoH. Repp (HaskinsLabs., 270 Crown St., New Haven, CT 06511-6695), H. H. Rump, and Speakingrate, focalstress, and sentenceposition can affectthe du- JacquesM. B. Terken (Inst. for PerceptionRes., 5600 MB Eindhoven, ration and spectralcharacteristics of vowels[e.g., B. Lindblom, J. The Netherlands) Acoust. Soc. Am. 35, 1773-1781 (1963)]. However prior researchhas beenless than conclusivein characterizingeffects of thesefactors [cf. Two experimentswere conductedto determinethe perceivedrela- e.g., T. (3ay, J. Acoust.See. Am. 63, 223-230 (1978)]. Previousfind- tive prominenceof two accentedsyllables within the same utterance. ings[D. M. Behneand L. C. Nygaard,I. Acoust.Sec. Am. 90, 2254(A) The fundamentalfrequencies (F0) at the two accentpeaks (PI,P2) (1991)] haveconfirmed the combinedeffects of thesefactors on vowel were varied as well as the rate of F0 declination over the unaccented duration and have shownthat vowelscan be independentlyaffected by syllables.Extending earlier work by Terken [J. Acoust. Soc. Am. 89, speakingrate, focal stress, and sentenceposition. The goalof thispaper 1768-1776 (1991)] with low-pitchedreiterant speech, a real Dutch is to characterizethe effectsof thesefactors on formant frequenciesof sentencewas employedin both femaleand male pitch ranges.The re- vowelsand relate them to effectson vowel duration.Using the vowels sultsconfirm earlier observationsthat P2 is usuallylower than PI when /•, o, a, •e/, conversationswere developedwith/kVt/and/kVd/as judgedto be equalin prominence,and that this differenceincreases with targetwords. In eachconversation a target word occurred in initial and PI height. However, this secondeffect diminishesas declinationrate in final sentenceposition and waseither focused or nonfocusedby the increases.The resultsdo not fit any simplemodel of prominenceper- discourse.Twelve subjectsproduced each conversation at three speak- eeptionbased on distancefrom a referencedeclination line. [Work car- ing rates.The presentresults demonstrated no effectof eitherspeaking ried out at IPO, Eindhoven.] rate or focal stresson the spectralcharacteristics of the vowels,but 5aSPS. Aural differentiationof related speakers. Winfried Krebber relativelyhigh first formant frequency and low secondformant frequen- and Vigo Rinas [Inst. for Commun.Eng., AachenUniv. of Technol. ciesfor vowelsin final sentenceposition compared to initial sentence (RWTH), Melatener Str. 23, D-52056 Aachen, Germany] position.These findings verify that speakingrate, focalstress, and sen- tenceposition can concurrentlyinfluence syllable-internal timing with Motivatedby the well-knownidentification problems in telephone distinct acoustic effects. The results will be discussed in terms of vowel communication,this studyinvestigates the influenceof filteringon the reduction and undershoot. aural differentiationof relatedspeakers (e.g., father and son). Speech 5aSPS. The influence of stress, vowel, and juncture cues on samplesof couplesof relatedspeakers were presentedto 30 listenersin segmentation. Paul N. ¾erkey and JamesR. Sawusch (Dept. of 14 sessions(1 couple/session).Each sessionstarted with a reference Psychol.,Park Hall, State Univ. of New York, Buffalo, NY 14260) sampleto acquaintthe listenerswith one speakerof the couple.Subse- quently the listenersreceived samples of both speakersand had to detect Cutler and Nortic [JEP:HPP14, I l•-121 (1988)] proposeda seg- the samplesbelonging to the acquaintedspeaker. Additionally they gave mentationstrategy based on strongsyllables. According to their strat- information about the certainty of their decision using the terms egy, a listenerattempts lexical accessever•j time a strongsyllable is "surely," "probably,"or possibly."The followingspeech samples were heard.In a word monitoringtask, Cutler and Norris found supportfor used: voiced vowels and (unknown) sentences,unfihered and filtered this strategywith speakersof British English.However, in the Cutler with severalbandpass filters; voiced vowelswithout higher formants and Norrisexperiments, the strongsyllables used were characterized by (only FI left), and whisperedvowels. In an additionalopinion test the strongstress, a tensevowel, and the possible presence of aliophoniccues similarity of both voicesof each couplewas rated. The rates of false to word junction.Thus the relativeroles of thesecues in segmentation identificationsdepend clearly on the filter bandwidth.For voicedvowels is still to be determined.As reportedat previousmeetings of the Acous- there is a goodcorrelation between the subjectivesimilarity and the tical Society,Yerkey and Sawusch[J. Acoust.Sec. Am. 91, 2338(A) ratesof falseidentifications, but not for sentences.Speech transmitted (1992}, J. Acoust.Sec. Am. 92, 2443(A) (1993)] examinedthis issue by usualtelephone handsets, applied with an acousticalleakage to the by separatingsyllable stress and vowel color in an attempt to determine ear, resultsin very high falseidentification rates (up to 45%). their relativeroles as cuesto segmentation.The resultsof theseexper- imentssuggest that, for AmericanEnglish, syllable stress is a primat3, 5aSP9. Acoustic features as indices of emotional responding cue for seRmentation.and vowel color doesnot •em to have an impor- following reward and failure feedback. Jo-Anne Bachorowski, tant influence.The presentstudy extends these results by evaluatingthe ChristopherD. Linker, and Michael L Owren (Dept. of Psycbol., Univ. of Colorado, Campus Box 173, P.O. Box 173364, Denver, CO role of allophonicjuncture in word segmentation. 80217-3364) 5a•P6. Development of the song selectivity by nonlinear neural rcspouse interactions in the zebra finch. Dukhwan Lim (Div. of Comprehensivemodels of personalityregard individual differences BioL, California Inst. of Technol., Pasadena,CA 91125) in emotionalresponding as important mediatorsof behavioracross a variety of contexts.However, traditional psychophysiologieal and self- The zebra finoh'ssong control systemcontains song-selective nen- reportmeasures are often unreliableor unwieldywhen applied to emo- rons. One of the song nuclei, hyperstriatum ventral, caudal (HVc) tional responses.Several acoustic features were examinedas indicesof receivesauditory inputsfrom the forebrainauditory area, field L, which changesin emotionalstate. Adult subjectswere given noncontingent is subdividedinto LI, L2, and L3. Where and how this selectivityis positiveand negativefeedback as they participatedin a computerized formed has not beenstudied quantitatively in this forebrainarea. The lexicaldecision task. Acoustic components were extracted from discrete

1880 J. Acoust.Soc. Am., VoL 94, No.3, Pt. 2, Sept.1993 126thMeeting: Acoustical Society of Amedca 1880 speechsegments recorded immediately following feedback. In compar- breath was replacedwith the sound of rustling leaves.The rustling isonto baselinerecordings, higher F0 valueswere associated with both sounds matched the breaths in duration and loudness. The results positiveand negative feedback. However, changes in jitter andshimmer shouldtell us whether the presenceor absenceof a breath beforea weredifferentially associated with the typeof feedbackin that increases synthesizedsentence functions as a cue for the upcomingspeech, or in theseperturbation measures were especially apparent following neg- merelyas a generalattention-orienting sound. [Work supportedby NIH ative feedback. The results of this research will be used to elaborate the Grant No. HD-01994.] cognitiveand emotionalprocessing of trait-anxiousand trait-impulsive individualsin contextsdesigned to engenderanxious and impulsivebe- 5aSPI3. The preliminary applicationof Gabor speetrogramanalysis havioralresponses. in speechsamples. Jack J. Jiang (Dept. of Otolaryngology--Head and NeckSurgery, Northwestern Univ., 303 E. ChicagoAve., Chicago, SaSPI0. Perceptionof multiple levels of prominencein spontaneous IL 60611), Shie Qian (Natl. Instruments,TX 78730), David G. speech.Colin W. Wightman (Dept. of Elec.Eng., New MexicoInst. Hanson, Eric Cuasay, and Jerilyn fogemann (Northwestern Univ., of Mining and Technol.,Socorro, NM 87801) Chieagn,IL 60611)

In both readand spontaneousspeech, phrasal prominences play an It hasbeen widely recognized that the FieF-basedspectrogram does importantrole in conveyingthe spcaker'sintent. Prominencesserve not providegood simultaneous resolution in both time and frequency bothto mark importantdiscourse-related events in the conversationand domains.A new methodof spectralanalysis has been developed based help to resolveambiguities at severallevels. Many speechresearchers upon the Gabor expansionand the Wignet-Ville distribution.The res- reportthe intuitionthat there are severallevels of prominence,that is, olution of the Gabor spectrogramis twice as high as that of a FFT- thatsome prominences are bigger than others. Nonetheless, attempts to basedspectrogram. In this report,FFT-based speetrograms and Gabor train human labelerato mark multiple levelsof prominencehave not spectrogramsare comparedfor 5 Englishvowels, 6 stopsconsonants, 4 beensuccessful: while therewas agreementon the locationof promi- fricatives, and vowelsformat transitionsin a CVD contentson 6 normal nences,there was little agreementbetween labelera on the level to be subjects.Results demonstrate that the Gabor speetrogramis a promis- assignedto each.Here, an alternativeapproach, using a panelof naive ing alternativefor FFrF-basedspectrogram in speechanalysis because of listenersto mark prominencesin a corpusof spontaneousspeech has its higher temporaland frequencyresolution. beentaken. Instead of markingmultiple levels of prominence,a simple binarylabeling was usedby eachlabeler and the levelof eachpromi- $aSPI4. Searching for attractors in speech and nouspeeeh nencedetermined by the numberof labeleramarking it. In this paper, respiration. Robert J. Porter (Kresge Hear. Res. Lab. of the South, the resultsof thispreliminary study are presented, and the relationships Dept. of Otorhinolaryngol.,Louisiana State Univ. Med. Ctr., New Orleans, LA 70112) and David .M. Hogue (Univ. of New Orleans, betweenthe estimatedlevels of prominenceand the acousticcorrelates New Orleans,LA 70148) of vowellengthening, syllable lengthening, and pitch level and excursion are investigated. Our recentstudy of breathingduring speech revealed that a nonlin- $aSPII. Inferring articulatory movementsfrom acousticproperties at ear equation,originally proposed as a descriptionof respirationduring fricative-vowel boundaries. forin Wilde (Res. Lab. of Electron., quietbreathing, may alsoprovide a descriptionof respiratorybehavior Dept. of Elec. Eng. and Comput.Sci., MIT, Rm. 36-547,Cambridge, duringspeech. This equationinterrelates variables such as lung volume, MA 02139} airwayresistance, and the durationof the utterance,and capturescom- monalitiesin the basicorganization of the respiratorysystem during Formant transitionsprovide context-dependent acoustic cues that what have been considereddifferent tasks or modes of behavior (i.e., can be interpretedin terms of the articulatory kinematicsinvolved in speechand nonspeech}.Further explorationsof thesedata suggestthat movingfrom a consonantto a vowel.Formant frequencies were mea- the mechanismunderlying the behaviormay be viewedas an attractor, suredat identifiedacoustic landmarks for eightEnglish fricatives pre- possiblychaotic. The presenceof suchan attractor in respiratorypat- cedingfront, back,and back-roundedvowels. Formant onset times des- terns is supportedby the findingsof other researchersand is consistent ignatedthe pointwhen the energyincreased most rapidly and evidence with the adaptivenature of the systemduring speech and nonspeech of the first formantwas first observed.Comparing the two-dimensional tasks[e.g., M.P. Sammonand E. N. Bruce,J. Appl. Physiol.70(4}, representationof F2 X F3 onsetfrequencies along the voicingdimension 1748-1762( 1991}]. Descriptionsof the attractorand someof its char- showedthe voicelessfricatives to be moredependent on vowelcontext. acteristieswill be presented. The onsetfrequencies for voicedfricatives reflect a more extreme su- praglottalposture, while the voicelessfricative measures can be consid- 5aSPIS. Velar coarticulationrevisited. FrederickaBell-Berti (Dept. ered to be at a point closerto the vowelbecause voicing begins at a later of Speech,Commun. Sci., and Theatre,St. John'sUniv., Jamaica,NY 11439 and Haskins Labs., 270 Crown St., New Haven, CT 06511), time relativeto the oral releasegesture. Formant structure in the noise before the release, to the extent that it is visible in the consonantal RenaA. Krakow (TempleUniv., Philadelphia,PA 19122and Haskins Labs.,New Haven, CT 06511), and Dorothy Ross (CUNY Graduate intervalprior to voicingonset, can provideadditional place information School, New York, NY 10036 and Haskins Labs., New Haven, CT for voicelessfricatives. Formant onset data are compared with measure- 06511} mentsreported from investigationsof placecategorization of stopcon- sonants.[Work supportedby NIH.] Severalmodels, embodying fundamentally different assumptions $aSPI2. Can you rustle up someattention?: Further resultson breath aboutthe natureand organizationof speechmotor control, have been soundsin synthesis. Sonya M. Sheffert (Haskins Labs., 270 Crown offeredin explanationof observationsof coarticulatoryphenomena. A St., New Haven, CT 06511, and Univ. of Connecticut), D.H. seriesof experimentshas beenundertaken to test specificpredictions Whalen {Haskins Labs., New Haven, CT 06511}, and Charles E. about the role of carryover coarticulationin delaying the normally sta- Hoequist {BNR, Inc., ResearchTriangle Park, NC 27709) ble onset of a velar gesture for a segment,made by BelI-Berti and Harris' coproductionmodel [F. Bell-Bertiand K. S. Harris, Phonetics During conversation,speakers typically take a breathwhen prepar- 38, 9-20 (1981}; F. l]ell-Berti, Phonet. Phonol.5, 63-85 (1993}]. For ing to speak.At the previousmeeting [Whalen and Hoequist,J. Acoust. example,the onsetof velar loweringfor a vowelor a nasalconsonant SOC.Am. 93, 2298(A) (1993}], it was shownthat subjectswere signif- followingan obstruentwill be delayeduntil nearthe endof the acoustic icantly more accurateat transcribingsynthesized sentences that were periodof the obstruent(depending upon its duration},to insureade- precededby a (naturallyproduced} breath intake than tho•e that were quate velopharyngealclosure for the obstruent.(That is, the velar ges- not. It wasconcluded that the perceptionof syntheticspeech is facili- ture for a later segmentis modifiedby the requirementsfor a preceding tated by the additionof a breath,presumably because it increasedthe one.) Early resultsencourage the beliefthat it will be possibleto ac- naturalheSSof the stimuli. However, there is the possibilitythat this countfor anticipatoryand carryover effects with a singlemodel. [Work resultis simplydue to the extra attention-gettingeffect of the breath supportedby NIDCD Grant No. De-00121to the HaskinsLaborato- betweenthe warningtone and the sentence.To test this possibility,the

1881 J. Acoust.Soc. Am., Vol. 94, No. 3, Pt. 2, Sept. 1993 126th Meeting:Acoustical Society of America 1881 SaSP16. The effect of !era-singdue to voice ussessmentin acoustic ing of the intelligibilityof selectedpassages of continuousdiscourse. analysisof vocal tremor in patients with Parkinson'sdisease. Judith Microphones,placed on KEMAR, recordedspeech stimuli embedded B. King (Recordingand Res. Ctr., Denver Ctr. for the Performing in cafeterianoise yielding S/N ratios of 0 and 8 dB SPL. Half of the Arts, 1245 ChampsSt., Denver, CO 80204 and Northern Arizona speech-in-noisestimuli were processed through the hearingaid digital Univ., Collegeof Health Professions,Box 15045,Flagstaff, AZ 8601! ), signalprocessor while half remainedunprocessed. The hearingaid pro- Ion H. Lemke (Univ. of Iowa, Iowa City, IA 52242), and William eessorutilizes a technologysimilar to adaptive-beamformingto reduce S. Winholm (Denver Ctr. for the Performing Arts, Denver, CO the maskingeffects of backgroundnoise on speechrecognition. Unproc- 80204) easedand processedspeech-in-noise stimuli were presentedto 10 nor- mally hearingsubjects, 10 hearing-impairedsubjects, and 10 hearing- For yearsresearchers have questioned the influenceof learningfrom impairedindividuals fit with linearamplification. Comparison of word baselineassessments. In a 3-yr study of 14 Parkinson'spatients who recognitionscores, reaction times, and intelligibilityratings for the two receivedno spe•h treatment,investigators studied phonatory variabil- S/N ratiosbetween unproeessed and processedspeech-in-noise stimuli ity and the effectof learningdue to voiceassessment. Statistically sig- suggestthat the hearing aid processingscheme provides significant ndicant constantdecline in weightedmean valueswere found to exist release-from-maskingeffects which may improve the recognitionof over time on acousticvariables of maximum performance.A strong speechin noisefor normally hearingand hearing-impairedlisteners. learningexperience as a resultof baselineassessment was also docu- mented.However, measures of maximumperformance are notoriously 5aSP19. Dishabituation of visual attention by natural and synthetic variable,potentially unstable and havebeen linked to effort,motivation, infent-direeted speechstimuli varying in spectral properties. Peter S. and learning.Therefore, the presentstudy was designedto examinethe Kaplan, MichaelH. Goldstein,and MichaelJ. Owren (Psychol.Dept., effectof learningreflected among the samegroup of 14 subjectsbut on Univ. of Colorado, P.O. Box 173364, Denver, CO 80217-3364) a more sensitive,less motivationallydependent phonatory variable. Amplitude-and frequency-demodulatedoutputs and measuresof fre- A habituation-dishabituationparadigm was usedto studyacoustic quencyand level (percent)of low-frequencyvocal tremor components characteristicsof adults'infant-directed (ID) speechthat elicit infant in sustainedphonation were analyzed. Growth curveanalysis models visualattention. Five groupsof 4-month-oldsreceived twelve 10s pre- were constructedto simultaneouslyestimate a constantrate of decline sentationsof a checkerboardpattern. On the ninth trial, one of five of the variablesover time (excludingthe influenceof baselinevalues) auditory stimuli was presented.Differences in looking duration were and to estimatethe effectof learningdue to baselineassessments. Pre- comparedon the trialsbefore and after the auditorystimulus. Attention liminary data from this studyenhance the understandingof the pro- increasedsignificantly after presentationsof a natural,intact ID speech cressirenature of Parkinson'sdisease among untreated subjects, and segmentand after a versioncomposed of sinewaves simulating its fun- further define which acoustic measures of voice are more sensitive to the damentalfrequency (Fo) and first five harmonics(Hi-Hs). However, effect of learning. [Work supportedin part by DC 00976 from the no significantchanges in attentionoccurred following sine waves sim- National Institute on Deafness and Other Communication Disorders; ulating the F 0 only, the F0-plns-Ht, or the harmonicsonly. The OrganizedResearch Grant, NorthernArizona University.] harmonies-onlystimulus elicited significantly less responding than did any other stimulus.The roles of frequencymodulation and spectml SaSP17. Changes in voice-onset time in speakers with cueMeat propertiesare discussed. implants. Harlan Lane, Jane Wozniak, Joseph Perkell, Melanie Matthies, and Mario Svirsky (Res. Lab. of Electron., Rm. 36-511, 5aSP20. Pereeptoal evaluation of infant artienlatory transitions. MIT, Cambridge,MA 02139) Naneye C. Roussel (Dept. of Cormnun. Disord., Univ. of SouthwesternLouisiana, P.O. Box 43170 USL, Lafayette,LA 70504} Voice-onsettime (VOT) was measuredfor the Englishplosives in and Raymond (3. Daniloff (North Texas State Univ., Denton, TX) /Co/•ontext spokenby three femaleand one male postlinguallydeaf- enedrecipients of multi-channelOneraid) cobhlearimplants. Record- The distributionof phonemi½cues containedwithin consonant- ingswere made of their speechbefore activation of their speechproces- vowel (CV) nonreduplicated(NRB} syllablesof infantsages 6 to 15 sorsand at intervalsafter activation, extending over several years. Also monthswas compared to thedistribution observed in adultproductions measuredwere: instantaneous oral airflow;sound pressure level; an in- IS. Furui, J. Acoust.Soc. Am. 57, 1016-1025(1986)] to examinethe direct index of giottal aperture;and averageairflow during passage extentof eoproductiveoverlap of infantconsonant and vowelgestures. readings.Pre-implant, all four speakerscharacteristically uttered plo- Truncatedversions of infant CV syllableswere presentedto adult lis- sireswith too-shortVOT, comparedto normafivedata. After activation tenersfor syllableidentification. Perceptual critical points (truncation of their processors,all four were relativelyaccurate in identifying point at which syllableidentification fell below 60% for the first time) sireswith respectto voicing,and the threefemale speakers lengthened were determinedfor both initial and final truncationconditions, and YOT.The women also increased glottal aperture post-activation. How- criticalintervals were calculated. Results revealed significant differences ever, none of the womenincreased peak oral flow followingplosive in the temporaldistribution and strengthof pbonemi½cues within the release,possibly because of a countervailingdecrease in subglottalpres- infant NRB CV syllable.Fewer than 1/3 of the infant syllablesdemon- sure: all three reduced SPL post-activation.Complementary results strated normal, adult-like identification functions under both initial and werefound for the malespeaker: a decreasein inferredglottal aperture final truncation conditions, and infant critical intervals were on the and an increasein oral flow accompaniedby an increasein SPL. In- average2«times longer than those of adult Japanese speakers. Results creasesin glottalaperture are expectedto inhibit the onsetof voicingin did not reveala clear developmentalprogression towards either more theplosives [K. Stevens,Phonefica •4, 264-279 ( 1977)].Consequently, adult-like critical interval durations or identification functions in the some or all of the observed increases in VOT with activation of the NRB syllablesstudied. implantprocessors may be due to "postural"adjustments of the larynx. $agP21. Intrinsic F0 in the babbling of infants at ages 6• 9, and 12 [Work supportedby N.I.D.C.D.] months. D.H. Whalen (HaskinsLabs., 270 Crown St., New Haven, 58SP18. Release-from-maskingeffects provided by a hearing aid CT 06511), AndreaG. Levitt (HaskinsLabs. and Wellesley College), digital signalprocessor. Michael A. Grim (Dept. of C.D.S.S., Univ. Iris Smorodinsky(Haskins Labs. and Yale Univ.), and Pai-Ling of Colorado,Campus Box 409, Boulder, CO 80309), Christopher Hsiao (Haskins Labs. and Univ. of Connecticut) Schwietzer, Eric Lindemann (AudioLogic, Inc., Gunbarrel, CO 80027}, and Richard H. Sweetman (Univ. of Colorado, Boulder, CO In adult speech,fundamental frequency (F0} has been found to {:• 803O9) relativelyhigh with high vowelsand low with low vowels.This "intrin- sicpitch" has been found in everylanguage examined, including tone Release-from-maskingeffects provided by a digitalhearing aid signal languages.One studywith infants[Bauer, Folia Phonia.40, 138-146 processorutilizing multiple-microphoneinputs were evaluatedwith ( 1988}]found that F0 changedconsistently with the front/backdimen- threemeasures of speechrecognition. Speech recognition measures were sionrather than the high/low dimension. Bauer interpreted this pattern monosyllabicword recognitionscore, reaction time, and subjectiverat- in termsof the changein vocaltract shape that occursover the first 18

1882 J. Acoust.Soc. Am., Vol. 94, No.3, Pt. 2, Sept.1993 126thMeeting: Acoustical Society of America 1882 monthsof life. In this study,four infantswere examinedat 6, 9, and 12 from its phase,the stimulusreconstructed from the amplitudewas monthsof age.Only vowelswith non-mid-centralarticulation were sc- foundnot of muchvalue in representingthe originalVCV signal.Little leeted. Results indicated that there was, after all, an associationwith improvementon consonantperception could be madeafter the itera- height,though there was also an interactionwith front/back.Reasons tionsifs fiat or a randomphase was taken as the initial guess.However, for the discrepancywith earlier work will be discussed.[Work sup- with an appropriatechoice of the initialguess, which contains one bit of portedby NIH Grant No. DC-00403.] the original phaseinformation, stimuli with near-perfectconsonant identificationperformance were reconstructed. 5aSP22. Childrenøscontrol of temporal variability in repetition tasks. BruceL. Smith and Mary Kay Kenney (Dept. of Commun. Sci. and 5aSP25. A multidimensionalscaling analysis of vowel discrimination Disord., Northwestern Univ., 2299 Campus Dr. N, Evanston, IL in humans and monkeys. Joan M. Sinnott, Charles H. Brown, and 6020g) ReginaA. Kressley (ComparativeHear. Lab., Dept. of Psychol.,Univ. of South Alabama, Mobile, AL 36688) Althoughseveral previous studies of normallydeveloping children haveexamined effects of speakingrate changeson segmentduration and Five humansand threeAfrican Sykes' monkeys (Cercopithecus al- variabilityand their possiblerelationship to neuromotoricmaturity for bogularis)discriminated among the ten Englishvowels using a repeating speech,there have been no investigationsconcerned with children's backgroundprocedure. Human subjectsare four native American- ability to directlycontrol the variabilityof their speech.The present Englishspeakers and one non-nativeHispanic speaker. Reaction times studyattempted to evaluatechildren's control of temporalvariability by wereinput to a multidimensionalscaling analysis (ALSCAL} in order assessingthe performanceof 7- to I l-year-oldsubjects who wereasked to derivea measureof perceivedsimilarity or dissimilarityamong the to minimizevariability in their speech.The tasksincluded: ( I ) a control vowels.For all subjects,including monkeys, the front vowelswere the condition,in which I 1 subjectsrepeated a variety of stimuli 25 times most distinguishablevowel group, while the central and back vowels each, with no specialinstructions as to how they were supposedto wereless clearly differentiated. The Hispanicspeaker performed simi- producethem, and {2} an experimentaltask, in which subjectswere larly to the native AmericanEnglish speakers, although Spanish does specificallyinstructed to be asconsistent as possible in repeatingstimuli not differentiateamong the spectrallysimilar vowels of English.One in an attemptto minimizevariability. Results indicate that for thegroup differencethat emergedbetween humans and monkeyswas that humans as a whole,the temporalvariability of variousspeech segments did not appearedmore sensitive than monkeysto first formantchanges in the tend to differ substantiallywhen comparingthe children'scontrol and frontvowels. [Work supportedby NIDCD.] experimentalproductions, with approximatelyhalf the subjectsshowing smalldecreases in variabilityand half showingsmall increases for the 5aSP26. Can lexical knowledgeinhibit phonemeperception? Lee H. segmentsthat weremeasured. It, thus,appears that for at leastthis type Wurm and Arthur G. Samuel (Dept. of Psychol.,State Univ. of New of repetitiontask, subjects perform at essentiallyoptimal levels, in terms York, Stony Brook, NY 11794) of variability, even when not specificallyattempting to do so. This seriesof experimentstests a critical predictionof the TRACE $aSP23. Syllable duration in Italian and Japanese, Laura Brighenti modelof speechperception [J. L. McClellandand J. L. Elman, Cog. ( Inst. for Speechand LanguageSci., New York Univ., New York, NY Psychol.lg, 1-86 (1986)]. Experiment I was a replication[73. H. 10003} and Peter Homel (Baruch College,CUNY, New York, NY Frauenfelder,J. Segui,and T. Dijkstra,JEP:HPP 16, 77-91 (1990}]. 10003} Subjectslistened to lists of wordsand non-words,and made speeded detectionresponses to specifiedphoneme targets. In accordwith the This studyanalyzes duration of stopsyllables in Italian and Japa- Frauenfelderet al. result,experiment I producedno evidenceof inhil> nese.Its resultsshow that the two languagesare verysimilar in termsof itory lexicaleffects on phonememonitoring reaction times. Experiment syllablelength. They also indicatethat, in accordancewith previous 2 improvedseveral design aspects of the Frauenfelderet al. experiment findings,both Italian and Japanesesyllable duration is contrasfivein by usingbalanced target locations,increasing the numberof critical termsof gemination,and Italian durationis alsocontrastire as a func- stimuli,and usinga moreappropriate baseline condition against which tion of stress.Finally, they showthat both languagespresent variability to measureinhibitory effects. The resultsof this line of researchclarify in the duration of their syllables,even in caseswhere the syllableis whether indirect lexical inhibition should be included in models of lex- neithergeminate nor stressed.These results point to the followingcon- ical access. clusions:(1} other elementsoutside the syllableitself (i.e., position within word, surroundingsyllables, information content, etc.} may be $aSP27. Lexical effects in nonwords? Rochelle Newman, James R. involvedin determiningsyllable duration; and (2) the stress-timed/ Sawusch,and Paul Luce (Dept. of Psychol., SUNY, Buffalo, NY syllable-timedlanguage distinction may not be usefulfor understanding 14260) how languagesassign duration for particularparts of the syllable.In particular,the resultsof this study indicatethat stressand syllable Previousresearch has reported the existenceof a "lexicaleffect" in positionplay an importantrole in determiningsyllable duration even in identificationtasks. For instance,one seriesmight rangefrom "dice" to syllable-timedlanguages. "tice," while the other variedfrom "dype" to "type." The ambiguous stimulifrom eachseries were more likely to be classifiedas membersof 5aSP24. Pereeption of stop consonants in speech signals the categorywhich makesa word. (Thus, they would be classifiedas reconstructedfrom phase or amplitude. L. Liu, J. L. He, and G. "d" in the dice-riceseries but as "t" in the dype-typeseries. } However, Palm (Dept. Nenroinformation,Univ. of Ulm, 7900 U!m, Germany) theseresults have sometimes been inconsistent, suggesting that factors otherthan lexical status are involved.In a seriesof experiments,pairs of It is well knownthat undercertain conditions, a signalis completely nonword-nonwordcontinua were presentedto listeners,where one end specifiedeither by its Fouriertransform phase or amplitude.An itera- of eachseries had a higherneighborhood density than the other end. tive techniquesimilar to that usedby Hayes et al. [IEEE Trans. That is, oneend of eachseries was similar to a greaternumber of words, Acoust.,Speech, Signal Process. ASSP-28, 672-680 (1980)] wasap- weightedaccording to frequencyof occurrence,than the other.Ambig- pliedto the globalFourier transform phases or amplitudesof natural uous items were classifiedby listenerswith the phoneticlabel corre- VCV (vowel-stopconsonant-vowel) utterances and the perceptionof spondingto thehigher density end of theseries. The resultssuggest that stopconsonants was experimentally studied. Under a varietyof condi- neighborhoodeffects may contributeto the variabilityin previous"lex- tions,the consonantidentification performance in the phase-onlystim- ical" effects.[Supported by NIDCD Grant No. DC00219 to SUNY at uli improvedfrom about 66% to more than 90% after the iterations. Buffalo and an NSF Graduate Fellowship to the first author.] The influenceof the initial amplitudeguess on the qualityof the recon- structedsignals was also investigated. The retrievalof stopconsonant $aSP28. Transformed auditory feedback: Effect• of fundamental informationfrom phasefor variouswindow lengths and variousphase frequency perturbation. Hideki Kawahara (ATR Human noiselevels were analyzed with regardto vowelcontexts, stop manner, Information Processing Res. Labs., 2-2 Hikaridai Seika-cho, andplace of articulation.In contrastto thecase of signalreconstruction Soraku-gun, Kyoto, 619-02 Japan)

1883 d. Acoust.Soc. Am., Vol. 94, No. 3, Pt. 2, Sept. 1993 126th Meeting:Acoustical Society of America 1883 A rapidinteraction between auditory perception and speech produc- Psychol.,Univ. of South Alabama,Mobile, AL 36688) tion has beenfound usingthe techniqueof transformedauditory feed- Four Sykes'monkeys (Cercopithecus albogularis) and threehumans back with fundamentalfrequency perturbation as the transformation. discriminatedamong 12 chirps presentedin a repeatingbackground The techniqueof transformedauditory feedback has been developed to paradigm.The teststimuli consisted of setsof four chirpsrecorded from investigatethe role of auditoryperception in speechproduction under Sykes' monkeys,red-tailed monkeys (Ce. ascanius),and small East natural conditions.The basicidea of the methodis to keepthe distur- African birds, respectivdy.Reaction times were submittedto a multi- banceof normalspeech production processes to a minimum,while al- dimensionalsealing analysis (ALSCAL). All monkeylisteners per- lowinginteractions between speech production and auditoryperception ceivedthe bird chirpsas similar to eachother, and distinctfrom the to be detectable.In the first experiment,subjects were instructedto monkey calls, while two of the three human listenershad difficulty sustainthe Japanesevowel/a/with a constantpitch. The phonated distinguishingthe bird chirpsfrom the monkeycalls. Both humanand vowelwas frequency modulated using sinusoids of 2- to 7-Hz rangeand monkeysubjects tended to exhibitoverlapping maps for the Sykes'and fedbackdiotically via headphones.The modulationdepth was 200 cent red-tailedcalls, but the magnitudeof overlaptended to be greatestfor from peak to peak. The resultsindicate that there is a phase-locking the monkey listeners.Guenon monkeysgive chirps in similar alarm effectin the fundamentalfrequency of the producedspeech. In a second contexts,and thesecalls alert membersof sympatricspecies to common experiment,a correlationanalysis using a pseudo-randomsignal as a dangers.Conversely, bird chirpsare very commonlyheard, are not modulatorrevealed that the reactionto fundamentalfrequency pertur- associatedwith alarm, and must constitutefor monkeysan acoustical bation is correctiveand that its latencyranges from 100 to 200 ms. Its impedimentto communication.The presentdata suggestthat the mon- relationwith the auditory-laryngealreflex will be discussed. key'sperceptual map of thesehighly similarcalls is influencedby the 5aSP29. The perceptionof chirps by Sykes' monkeysand humans. biologicalsignificance of these calls in nature. [Work supportedby CharlesH. Brown,Joan M. SinnoR,and ReginaA. KressIcy (Dept. of NIDCD.I

FRIDAY MORNING, 8 OCTOBER 1993 COLUMBINE ROOM, 7:55 A.M. TO 12:00 NOON

Session 5aUW

Underwater Acoustics:Propagation

Kevin L. Williams, Chair /lppliedPhysics Laboratory, University of Washington,Seattle, Washington 98105

Chairs Introductionm7:5$

Contributed Papers

method [M.D. Collins, J. Acoust.So:. Am. 93, 1736-1742 (1993)]. Severalof the derivativesare correctat the originfor Pad• approxima- SaUWI. Implementation of generalized impedance boundary tions. Improvedefficiency may be achievedby usingrational approxi- condition hi the split-step Fourier parabolic equation. F. J. Ryan mationsdesigned using the minimax method,which involvesminimiz- (Ocean and AtmosphericSci. Div., Code 541, NRaD, San Diego, CA ing the maximum error over a domainof interest.This approachhas 92152-5OOO) beenapplied for derivinga PE for fluid mediathat handleswide prop- The parabolicwave equation (PE) is a powerfulnumerical method agationangles [Vefring and Mjalsnes,J. Acoust.Soc. Am. 93, 1736- for computingthe full-wavecomplex acoustic pressure field in range- 1742( 1993)1.Additional applications of the minimaxapproach include dependentenvironments. The split-stepFourier PE algorithm (SSFPE) deriving improvedapproximations for the elasticPE (for which stabil- of Hardin and Tappert providesa very efficientcomputational imple- ity is an importantissue), the two-wayPE (which may requirea careful mentationof PE when the surfaceboundary condition is of the Dirichlet treatmentof the evanescentspectrum ), and the split-stepPad6 solution or Neumann form, and when the solutiondecays sufficiently with depth. (which involvesthat approximationof a relativelycomplicated func- This allowsuse of fast Fourier transform(FFT) methodsto implement tion). the SSFPEalgorithm. Typically the infinitedomain radiation condition is approximatedon a finite calculationgrid by employingan artificial 8:30 absorberor sponge.In somecases involving strong bottom interaction, however,the requiredabsorber region may be quitelarge. This resultsin $aUW3. Comparisonof a parabolicequation model with Gaussian an increasedcomputational load. A new method for truncatingthe beam tracing in range-independent and range-dependent absorberregion will be describedthat is basedupon splittingthe PE environments. Timothy H. Ruppel and Robert L. Field (Naval Res. field into two componentsthat are in turn propagatedon differentver- Lab., StennisSpace Center, MS 39529) tical wave-numbergrids. Illustrative exam•at useth•s new method will be shown.[Work supportedby NRaD IR program.] Transmissionlosses predicted by the parabolic equation model FEPE over a 20- to 150-Hz frequencyband are comparedwith trans- missionlosses predicted by Gaussianbeam tracing in range-independent 8:15 and downslopeenvironments. Ocean impulse responses, computed with 5aUW2. Minimax rational approximationsfor the parabolic equation each model, are also compared with experimentallydetermined re- m,Rhod. Michael D. Collins (Naval Res. Lab., Washington,DC sponscspreviously reported. [R. L. Field and J. H. Leclere,J. Acoust. 20375} Soc.Am. 93, 2599-2616( 1993)].As in the earlierpaper, environmental inputsto the modelare derivedfrom the OceanDrilling Project(ODP) Higher-orderPad6 approximations have been applied to reducethe sitesnear the experimentlocation, and impulseresponse comparisons limitationsand to improvethe efficiencyof the parabolicequation (PE) aremade using correlation coefficients. [Work supportedby theOffice of

1884 J. Acoust.Soc. Am.,VoL 94, No. 3, Pt. 2, Sept. 1993 126th Meeting:Acoustical Society of America 1884 Naval ResearchProgram Element 0602435, with technicalmanagement For methodsthat require numerical solutions of the verticalwave func- providedby the Naval ResearchLaboratory.] tionsthe computationof the matrixelements is very time consuming and can evenlead to inaccuraciesat higherfrequencies. However the closedform solutionsallow one to code matrix elementsin relatively 8:45 simpleclosed form basedon simplearithmetic sums. This leadsto a 5aUW4. Modeling acoustic particle velocity in range-dependent rapidmethod for generatingthe projectionmatrices and thereforecon- environmentswith a paraboliceqantion code. K. B. Smith, G. L. nectsthe stepwisedomains in a rapid fashion.The methodis testedand D'Spain,and W. S. Hodgkiss (Marine Phys.Lab., ScrippsInst. of comparedwith otheravailable coupled mode programs. Ultimately the Oceanogr.,San Diego, CA 92152-6400) methodwill be usedfor the objectin a waveguideprogram for which this methodwas originally designed. [Work supportedby Naval Re- Measurementshave been made of theacoustic particle velocity field searchLaboratory 6.1 program(element 601153N) with technical generatedby a towedsource transmitting 7-, 10-,and 16-Hz tones. The managementprovided by NRL-SSC.] periodicchange in the polarizationof the motionas a functionof source-receiverrange, from progradecircular motion to retrogradecir- 9:45 cular motionand back,appears to havebeen disrupted by changesin slopeof the bottomtopographic features in theexperiment. In orderto 5aUWS. New algorithm for calculatingnormal modesin broadband test this hypothesis,the Universityof Miami parabolicequation code applications.Robert A. Koch and D. P. Knobles (Appl. Res. Lab., (UMPE) was modifiedin order to efficientlycalculate acoustic particle Univ. of Texas, P. O. Box 8029, Austin, TX 78713-8029) velocity.This numericalcode makes effective use of the equivalentfluid approximationfor low shearspeed ocean bottoms [C. T. Tindieand Z. A newalgorithm for calculatingthe normalmodes that are usedto Y. Zhang,J. Acoust.Soc. Am. 91, 3248-3256(1992)]. The predictions describeunderwater acoustic propagation is presented.The algorithmis of the UMPE modelarc comparedwith the actualmeasurements, and especiallyrelevant for broadbandnormal mode calculations in which with the predictionsmade by the finiteelement parabolic equation normalmode eigenvalues, depth functions, and attenuations are needed. (FEPE) by M.D. Collins,which explicitly incorporates the effectsof The new algorithmuses an expansiontechnique to constructnormal bottomshear. [Work supportedby ONR.] modeeigenvalues and depthfunctions for somefrequency from eigen- valuesand depthfunctions previously calculated at another,higher fre- quency.Comparisons of theestimated eigenvalues, depth functions, and 9:00 attenuationswith exactresults are presentedfor severalshallow water environments.A broadbandpropagation model that usesnormal mode 5aUW-•. Long-range acoustic propagation in four dimensions. setscalculated with the new algorithmhas been developed. Transmis- Gregory J. On'is and Michael D. Collins (Naval Res. Lab., sionloss and impulseresponses based on estimatedand exactnormal Washington,DC 20375) modesets are compared.[This work wassupported by the Officeof Oceanacoustic modeling is usuallyrestricted to frequency-domain NavalResearch through Block RL3B andBlock CS3A.] problemsin two dimensions.Since ocean acoustics problems typically involvedomains that arc verylarge relative to a wavelength,computa- 10:00-10:15 Break tiontimes often become prohibitive when a thirddimension (either time or thethird spatial variable) is included.The adiabatic mode parabolic equation(PE), whichhas been applied to solveglobal-scale problems in 10:15 threespatial dimensions [Collins et aL, J. Acoust.Soc. Am. 93, 2321 $aUW9. Three-dimensional modeling of acoustic pulse propagation (1993)], is practicalfor solvingfour-dimensional problems out to long through shallow water. Robert T. Chapman and Donald J. range(i.e., hundredsof wavelengthsor more). In the time domain,the McDowell, $r. (Naval Undersea Warfare Ctr., Div. Newport, adiabaticmode PE solutionillustrates the flow of energyin the modal Detachment New London, Code 423, New London, CT 06320) coefficients,which dependon rangeand azimuth. A three-dimensionalmodel capable of simulatingthe propagation, scattering,and reverberationof acousticwaveforms with an arbitrary 9:15 time dependenceis presented.The finiteelement method is usedto 5aUW6. Propagationand signalcoherence in bottom-limitedshallow modelthe spatialcharacteristics of the shallowwater domain. An ex- waterenvironments. F.J. Ryan (Oceanand AtmosphericSci. Div., plicitintegration scheme is usedto obtainthe time-dependent pressure Code 541, NRaD, San Diego, CA 92152-5000)and L. A. Shook fieldsolution, for the entirecomputational space, due to a prescribed (NRaD, San Diego, CA 92152-5000) sourcefunction. Multiple independentsources, depth- and range- dependentbathymetry, volumetric scattering, fluid sediments, and scat- Simulationresults will be presentedfor complexshallow water en- teringfrom irregular bottom topography may be consideredwith this vironmentsoff the southernCalifornia coast. The studyfocuses on down- modelingtechnique. As implemented,the computationalscheme uti- slopepropagation from sourcesin shallowwater to deeperbottomed lizesenhanced supercomputer vector processing, and an element-by- sensors.The environmentis a thinly sedimentedseries of terracessep- elementstorage strategy to enhancethe computationalefficiency and aratedby steepslopes. A veryhigh fidelity geoacoustic bottom model, feasibilityfor thethree-dimensional, time-dependent problems of inter- SEABEAM-typebathymetry and densesynoptic oceanographic mea- est.Computational results will be presentedfor the propagationof a surementsare used to computepressure fields using PE codes.Examples finiteduration pulse from a pointsource in deepwater, up a sloping of spatialsignal coherence and spatial variability will be shown.The bottom,into shallowwater. [Work supportedby the NUWC IR and questionof theeffects of environmentaldata spatial resolution (bathym- IED programs.] etry andsub-bottom) on computedsignal fields will be addressed.

10:30 9:30 5aUWI0. Faetorization of propagator matrices for efficient 5aUW7. A fast one-waynormal mode propagation method. E. White computationof wave-fieldsin horizontallylayered fluid-solid media. andM. F. Werby (NRL, TheoreticalAcoustics, Code 7181, Stennis SvenIvansson [Dept. of Hydroacoust.and Seismol.,Natl. Defence :•pace Center, MS 39529) R½•. E•tabli•hmcnt (FOA 260), •-172 90 •undbyberg, gweden] Thedevelopment of a newfast normal mode method produces ver- The wavefield is decomposedinto its frequency-wave-numbercom- tical wave functionsthat are in closedform. One-way coupledmode ponents.Compound matrices for solid layers provide a convenientway methodscan be basedon projectionmatrices that are generatedby of computingthe boundary values at a fluid-solidinterface [M. B. Por- integraloverlaps between vertical wave function of adjacentdomains. ter and E. L. Reiss,J. Acoust.Soc. Am. 77, 1760-1767(1985)], with

1885 J. Acoust.Soc. Am., VoL 94, No.3, Pt.2, Sept.1993 126thMeeting: Acoustical Society of America 1885 loss-of-precisioncontrol. A certainvector is propagatedthrough a se- 11:15 quenceof multiplicationswith compoundmatrices, one for eachlayer. 5aUWI3. Some observationsof aeonstic variability and array It is shownthat computationsof this kind can be performedmore performanceat short range near Vestijorden. Donald R. Del Balzo efficientlyif each compoundmatrix is decomposedas a productof (SACLANT UnderseaRes. Ctr., Viale San Bartolomen,400, 19138 La sparsematrices that areapplied in sequence.Two kindsof compound- Spezia,Italy) matrixfactorizations are proposed.In connectionwith dispersioncom- putaflons,our first factorizaflongives a methodthat is relatedto the An experimentwas conductedin October 1999 in shallow water "fastform" of Knopoff'smethod [F. Schwabeta!., Bull. Seismol.Sec. (250-320 m) near Vestljordenin supportof sonarsystem research at Am. 74, 1555-1578 (1984)]. This algorithmis slightlymore efficient, SACLANTCEN. This talk describes some observations of acoustic vari- however,and its rangeof applicabilityis wider. The secondcompound- ability and array performanceat short rangefor one-waypulse propa- matrix factorizationgives a methodthat is significantlyfaster than the gationduring a 46-minperiod. The signalswere 0.5-s LFM pulsesin the "fast form" of Knopoff'smethod. Very few arithmeticoperations are frequencyband of 340-345 Hz. They were receivedat a rangeof 13 km needed.It alsoprovides a goodbasis for analyzingthe numericalper- on 59 elementsof a towed array. Large variability in the receivedsignal formanceof compound-matrixpropagation. Finally, it is shownhow level acrossthe army, by as much as 10-15 dB, was observedon some propagator-matrixfactorization can be usedto enhancethe efficiency individual pulses.These acousticvariations appear to be related to for mulfl-frequencycomputations and computation of full wave-fields, depthvariability along the army dueto a smallarmy flit. Normal mode by wave-numberintegration or modalsynthesis. calculationsin this environmentindicate the existenceof a deepacoustic null in the vicinity of the measureddata. Average array signal gain 10.-45 degradationfor all data with SNR> 20 dB is only 0.6 dB, so the array beamformingperformance is closeto the theoreticalmaximum on this $aUWI1. Analysis of the aenustic field via spectral decomposition. 27-wavelengthaperture in shallowwater. Guy V. Norton (NRL-SSC, StennisSpace Center, MS 39529-5004)

Spectraldecomposition has beenused by variousauthors as a cal- culationtechnique for acousticpropagation in rangeindependent and 11:30 recentlyrange dependentocean environments. One of the methods' SaUW14. Shell function method inenr9orated ray representationfor strongpoints is that it mapsthe initial acousticfield at eachgiven depth enmputing the acoustic pregsure field in inhomogeneousmedia. point in the waveguideinto horizontalwavenumber space. Since the Haitao Pan and ShigeoOhstuki (Precisionand IntelligenceLab., fieldis nowexpressed in wavenumberspace, analogous to normalmode Tokyo Inst. of Technol.,Nagatsuta 4259, Midori-ku, Yokohama,227 theory,various acoustic quantities can easily be calculated. These quan- Japan) tifiessuch as the groupvelocity or the incidentfield expressed in terms of the planewave spectrum in the past were calculatedusing normal The Shell function method is presentedas a new techniqueto eval- modes.However, since all that is requiredto initiate the methodis a uate the acousticpressure field, producedby a practicalsource of finite complex acousticfield evenly spacein depth of the waveguide,the area, in a medium havingan arbitrary spaticilyvarying sound speed. method has been coupledto the output of a PE model, in order to The Shell function method considers the acoustic wave received at the analyzethat field. The associatedtheory and numericalexamples will be observationpoint, for a specifiedtravel time, and the associatedvibrat- given.[Work sponsoredby ONR.] ing sourcearea• In termsof ray representation,this approachis accom- plishedby interchangingthe positionof the observationpoint with that 11.-00 of the elementalarea of the source.Both the convergentstate of a sound beam issuingfrom the observationpoint, and the elementarea of the $aUWI2. Frequency-dependentsound attenuation in the northeastern sourceresponsible to this convergentstate, are taken into accountsi- Pacific Ocean below 400 Hz, Gerald B. Morris (Code 7172, Naval multaneously.As a consequence,the soundpressure at, and in the Res. Lab., StennisSpace Center, MS 39529) vicinityof, causticscan be givenan appropriatevalue directly. The Shell functionmethod was evaluated by the computationof the acousticfield Signalsfrom SUSexplosives were received at four hydrophonessns- pendedin the deepocean from the ResearchPlatform FLIP. Energy in a depth-dependentsound-speed profile containing caustics, for a lin- flux densitieswere determinedfor approximately700 of thesebroad- ear sourcewith a specifiedlength. bandsources at rangesfrom 70 to 1250nmi. The normalapproach in determiningattenuation is to calculatethe transmissionloss with no 11:45 frequency-dependentattenuation as a functionof rangeusing a numer- ical model,subtract the calculatedspreading loss and attributethe re- 5aUW15. The calculationof time domain signalsin a waveguidewith mainingloss to frequency-dependentattenuation. Because of the large applications. M. F. Werby and E. White (NRL, Theoretical lossesdue to geometricspreading and small lossesfrom the attenuation Acoustics,Code 7181, StennisSpace Center, MS 39529) togetherwith the stronglyrange-dependent environment calculating the spreadingor transmissionloss with high accuracyis difficult.An alter- A fast normal mode codehas beendeveloped that is basedon an nate techniquewas used.Differences in measuredpropagation losses at expansionmethod and a fast Fourier transform integral method.This variousfrequency bands up too 400 Hz were usedto calculaterelaflvc has enabledone to performbroadband pulse calculations to high fre- lossesreferenced to a band near 50 Hz. Assumptionswere then made quenciesquickly. Further the pulse returns can be decomposedinto regardingthe functionalform of the frequencydependency of these their constituentmodes. Studies on pulsereturns were performedfor lossesand the resultingfrequency-dependent attenuation losses deter- realistic shallow water waveguides for signals out to 25 krn and the mined. The resultingvalues are consistentwith a boric acid relaxation variousdispersion effects and separatemodel arrivals with increasing frequencyof I kHz, but the losscoefficient is lowerthan thosepredicted distancefrom the sourcewere illustrated. Particular emphasis is placed from Thorp'sequation. These results are in agreementwith published on strongchanneling. [Work supportedby Naval ResearchLaboratory valuesdetermined for higher frequenciesfrom cw acoustictransmis- 6.1 program(element 601153N) with technicalmanagement provided sionsin the sameregion. [Work supportedby ONR.] by NRL-SSC.]

1886 J. Acoust.Soc. Am., VoL 94, No. 3, Pt. 2, Sept. 1993 126thMeeting: Acoustical Sociely of America 1886 FRIDAY AFTERNOON, 8 OCTOBER 1993 MAJESTIC BALLROOM, 1:00 TO 3:30 P.M.

Session5pSP

SpeechCommunication: Applications of SpeechPerception Research in DisorderedPopulations

Brad S. Rakerd, Chair Departmentof Audiologyand SpeechScience, Michigan State University,East Lansing, Michigan 48824

ContributedPapers

1.-00 1:30

5pSPI. Speechperception without audition. LynneE. Bernstein (Ctr. $pSP3. Evaluating the articulation index for auditory-visual for Auditoryand SpeechSci., Gallaudet Univ., 800 FloridaAve., N.E., consonantrecognition. Ken W. Grant and Brian E. Walden (Walter Washington,DC 20002) and Marilyn E. Demorest (Univ. of Reed Army Med. Ctr., Army Audiol. and SpeechCtr., Washington, Maryland,Baltimore County, Baltimore, MD 21228) DC 20307-5001 )

Mostknowledge about speech perception is withinthe framework of The ANSI standardfor calculatingthe articulationindex [ANSI studiesconcerned with acoustic-phoneticstimulus attributes. Vision is S3.5-1969(R1986)] includesa procedurefor estimatingthe effectsof knownto affectspeech perception but is typicallyconsidered only as a visualcues on speechintelligibility. This procedureassumes that listen- supplementto hearing.The literaturecontains assertions that only 30% ing conditionswith the sameauditory articulationindex (AI^) will of wordsare recognizedin lipreading/spcechreadingand that hearing have the same auditory-visualAI (AI^v) regardlessof the spectral subjectsare moreaccurate than deaf subjects.Observations of expert compositionof the signal.In contrast,other studies have suggested that visualspeech perception among some profoundly deaf subjects[L. E. the redundancybetween A and V speechcues might be a betterpredic- Bernsteineta!., J. Acoust.Soc. Am. 90, 2971-2984(1991)] promoted tor of AV performancethan eitherthe AI A or the overall(e.g., percent questioningof the conventionalwisdom. A normafivestudy of lipread- correct) auditory recognitionscore. In the presentstudy, the ANSI ing was thereforeconducted involving 96 hearingand 72 deaf young procedureis evaluatedby measuringA, V, and AV consonantrecogni- adults.The two populationsdiffered significantly across nonsense sylla- tion undera varietyof differentsignal-to-noise and bandpass-filtered ble, word, and sentenc• identification measu•s. The most accurate sub- speechconditions. The resultsindicate that auditory conditionshaving jeerswere from within the deaf population.Results that lipreadingin the sameA! A do not necessarilyresult in the same AIAv, and that some deaf subjectsis comparableto listeningto speechin noiseby low-frequencybands of speech tend to provide more benefit to speechreadingthan high-frequencybands of speech.Analyses of the hearingsubjects. Expert lipreading demonstrates that speeehperception auditory error patterns producedby the different filter conditions doesnot requireaudition. Speech perception appears to be fundamen- showeda strongnegative correlation between the degreeof A and V tally the p•rceptionof linguisticentities not acoustic-phoneticat- redundancyand the AV benefitobtained. These data indicate that the tributes.Theories of speechperception for which generalityis claimed ANSI procedureis inadequatefor predictingAV consonantrecognition needeither to accountalso for visualspe•h perceptionor needto limit performanceunder conditionsof severespectral shaping. [Work sup- their claimsto generality. portedby NIH Grant No. DC00792.]

l:lS

SpSP2. Stimulus materials for audio-visualstudies of attention and $•P4. Abstract withdrawn. speechperception by the hearingimpaired. Brad Rakerd (Dept. of Audiel. and SpeechSci., Michigan State Univ., East Lansing, MI 48824) and Philip F. Seitz (Gallandet Univ., Washington, DC 20002)

Individualswith sensorineuralhearing impairment have been shown to devotea larger than normalshare of their attentionto speechpro- cessingwhen listening in situationsthat affordaccess to audiospeech cuesonly. Attentionalcommitments may proveto be more nearlynor- mal if both audio and visual speechcues are available.To test this possibility,a studio-qualityvideotape has beendeveloped for usein primary-taskand dual-taskstudies of attentionand speechperception. Markers on the tape make it possibleto maintain coordinationwith a computer.The timing of speechevents is specifiedto within a few milliseconds,potentiating subject reaction time measurements.There are threesets of stimulusmaterials: (i) 30 to 45ssamples of connected discourse;(ii} tripletsof phoneticallybalanced monosyllabic words, arrangedin an ABX format for discriminationexperiments; and (iii) randomizedlists of wordsand phoneticallymatched nonwords for lex- ical decisionexperiments. Copies of the videotape,along with support- ingsoftware and other test materials, are available upon request. [Work supportedby NIH-NIDCD.]

1887 J. Acoust.Sec. Am.,. VoL 94, No. 3, Pt. 2, Sept.1993 126thMeeting: Acoustical Society of America 1887 1:45 suitsfrom 19 normalheating subjects showed the ILDs alonebenefited the listenerslightly more [3.97-dBimprovement in sentencespeech re- 5p•PS. Relationshipbetween identification errors and spectraldetails ceptionthreshold (sSRT) versusa 0-deg condition]than ITDs alone of naturally produced diphthongs. Anna K. Nabelek, Zbigniew (3.22-dB improvementin sSRT), as comparedto 6.21-dBimprovement Czyzewski,and Hilary CrowIcy (Dept. of Audiol. and SpeechPathol., in sSRT when both ILDs and ITDs are present.If the sSRT is calcu- Univ. of Tennessee, 457 South Stadium Hall, Knoxville, TN lated relative to the noise level in the shadowedear, the ITDs alone 37996-0740) producedthe samesSRT as ITDs and ILDs together.Data from hear- In an earlier study [A. K. Nabelek et al., J. Acoust. SOc.Am. 92, ing impaired listenerswill also be presented. 1228-1246 (1992)], identificationerrors were collectedfor 15 English vowels,monophthongs, and diphthongs.The vowelswere produced in a 2:30-2:46 Break /b-t/context by six male talkerswho utteredfive tokensof eachvowel. There were 20 normal-hearingand 20 hearing-impairedsubjects. Lis- 2.'45 teningconditions were quiet, noise, and reverberation.Large differences in numberof errorswere observed among the 30 tokensof eachvowels. 5pSPS. Effects of hearing differenceson encodingand comparison The goal of the currentstudy was to determinerelationships between information-processingstages. Philip F. Seitz (Ctr. for Auditoryand the spectraldetails of the diphthongs/m, •, ou/ and identification SpeechSci., Gallaudet Univ., Washington,DC 20002-3695), Brad errors. Spectralanalyses indicated that all three diphthongshad two Rakerd (Michigan StateUniv.), and Paula E. Tucker (Gallaudet distinctsegments. In the first segmentFI and F2 were relativelysteady Univ.) stateand in the secondsegment F2 changedover time. For eachtoken of each diphthong, frequenciesand levels of FI and F2 were traced Reactiontimes to spokendigits presentedin a speededmemory alongthe durationof the diphthong.The resultsof this analysisseem to scanningprocedure were measuredfor groupsof listenerswith normal indicate a relationshipbetween the number of identificationerrors for hearing(N=24) and with congenitalor early-onsetsensorineural hear- thesediphthongs and the relative levels of the F2 transition segment. ing losses(N= 12). Separategroups of 12 normal-heatinglisteners were Examplesof highlyidentifiable and high confnsablediphthongs will be testedunder conditionsof goodstimulus quality (no distortion,high shown.[This work wassupported by NIDCD.] SNR) versuspoor stimulusquality (low-passfiltered, low SNR). The speededmemory scanningprocedure allows total reactiontime to be decomposedinto "encoding"and "comparison"components which cor- 2:00 respondto separatestages in a modelof humaninformation processing. At issuehere is whetherlong-term effects of hearingloss, such as pos- 5pgP6. Mutual dependenceof octave-band contributions to speech sibledeficits in phonologicaland/or lexicalrepresentation of spoken inte!ligibi!ity. Herman J. M. Steeneken (TNO Inst. for Human language,lead to unusualprocessing costs at either the encodingor Factors, P.O. Box 23, 3769ZG, The Netherlands) comparisonstage. Experimental results suggest that impairedlisteners Currentobjective measures for predictingthe intelligibilityof speech incur the sameencoding costs as normal-hearinglisteners presented assumethat this can be modeledas a simpleaddition of the contribu- with poor-qualitystimuli. However, comparison costs for the impaired tionsfrom individualfrequency bands. The articulationindex (AI) and listenersare no higherthan thosefor the normal-heatinglisteners pre- speechtransmission index {STI) arebased on thisassumption. There is sentedwith good-qualitystimuli, and are unexpectedly lower than those evidencethat the underlyingassumption of mutuallyindependent con- for the normal-hearinglisteners presented with poor-qualitystimuli. tributionsis not valid and may leadto erronconsprediction for condi- [Work supportedby NIH-N1DCD.] tionswith a limitedfrequency transfer, with spectralgaps or with spec- trally localizedmasking. An experimentwas performed focused on the 3:00 contributionsfrom individualfrequency bands. For this purposethe speechsignal was subdivided into 7 octavehands with centerfrequen- 5pSP9. Speechrecognition and frequencydiscrimination with the cies rangingfrom 125 Hz to 8 kHz. For 26 differentcombinations of 3 Incraid and CIS eochlearprostheses. M. F. Dotman (Dept. of or more octave bands the CVC-word score (consonant-vowel- Speechand Hear. Sci., Arizona StateUniv., Tempe, AZ 85287-0102) consonant,nonsense words) was obtainedat three signal-to-noiseratio. Measuresof frequencydiscrimination and speechunderstanding /:or an improved prediction of the observedintelligibility, a revised weremade for cochlearimplant patients using the Incraid, analog signal modelwas designedthat accountsfor mutual dependencybetween ad- processorand for patientsusing the continuousinterleaved sampling jacent octave bands by the introduction of a redundancycorrection (CIS) processor.For patientsusing the Ineraid,measures of frequency (secondorder cross-p•oduct terms). A similarmodel was found for discriminationare significantlycorrelated with performanceon testsof male and female speech.The data also provideda verificationof the speechunderstanding. The correlationcoefficients range from 0.60 to relationbetween signal-to:noise ratio and the contributionto the STI. 0.82 dependingon the frequencydomain of the discriminationtest and on thenature of thetest of speechunderstanding. When Incraid patients 2:15 were fittedwith a CIS processor,speech understanding improved sig- nificantly.An improvementin frequencydiscrimination may be the 5pSP7. The separate contrib-tion of head-shadow and binaural principalfactor in the highword recognition scores achieved by patients interactions to directional hearing in noise. Michael J. Nilsson, usingthe CIS processor.[Research supported by NIDCD.] Sriram Jayaraman,and Sigfrid D. SOli (House Ear Inst., 2100 West

Third St., Los Angeles,CA 90057) 3:15 A replicationof Bronkhorstand Plomp [J. Aconst.Soc. Am. 83, 5aSPI0. $peaker-inde!•ndentreengnition of children's words with 1508-1516(1988)] was Undkrtaken to study the separate contributions minimal phonerolecontrast. Diane Kewley-Port, Bill Mills, and of interaurallevel differences(ITDs); producedby head shadow,and Jonathan Dalby (Commun. Disord. TechnoL, 205 $. Walnut, interauraltime differences(ITDs), which producebinaural interac- Bloomington,IN 47404) tions,to directionalhearing in noise.Digital filtering of speechand noise signalswas performedusing head-related transfer functions (HRTFs) Speaker-independentspeech recognition can be usedin speechtrain- measuredon a ICEMAR mannequinto simulatesound field conditions ingapplications to providefeedback on phonemiccontrasts. Our appli- under headphones.Speech materials from the heating in noise test cationis drill for normal-heatingmisarticulating children with target- (HINT) were presentedat a simulated0-deg azimuth, while a noise substitutionerrors (e.g., /r/•/w/ or /sly/O/). Six word pairs signalmatched to the spectralshape of the speechwas filtered to include incorporatingeight commonmisarticulations in word initial, roedial, the ILDs and 1TI• from eithera 0-, 90-, or 270-degpresentation, and final positionswere repeatedtwice for a total of 192 words.These includingmixed combinations, e.g., 0-deg ILDs with 90-degITDs. Re- phonemiecontrasts are extremely challenging for mostrecognizers. Sev-

1888 J. Acoust.Soc. Am., Vol. 94, No..3,Pt. 2, Sept.1993 126thMeeting: Acoustical Society of America 1888 entecnchildren in third to fifth graderepeated the word list once.Two recognitionof a subsetof the wordswas alsoshown to vary across other childrenand an adult repeatedit seventimes to providespeaker- phonetalccontrasts. Analyses of thelinguistic content of theword pairs dependentcomparisons. The Scott SIR 20 recognizerwas evaluated. and comparisonswith the speaker-dependentrecognition results indi- Speaker-independenttemplates were made in round-robinfashion, leav- catethat speaker-independentrecognition is accurateenough for some ing out onechild each time for testing.The overallrecognition rate for the 16 testswas 75.3% correct,with a rangeof 85.3% for the best minimalphonemic contrasts to beused in speechdrill. [Worksupported (/s-J/) phonemiccontrast, to 65.5% for the worst(/d-6/). Human by NIDCD.]

FRIDAY AFTERNOON, 8 OCTOBER 1993 COLUMBINE ROOM, 1:00TO 4:00 P.M.

Session5pUW

Underwater Acoustics:High-Frequency Acoustics in the Upper Ocean

Ralph R. Goodman,Chair AppliedResearch Laboratory, Pennsylvania State University, State College, Pennsylvania 16804

Chair's Introduction--l:00

Invited Papers

1:05

5pUW1.Ocean surface processes affecting high-frequency acoustics. W. KendallMelville (ScrippsInst. of Oceanogr.,Univ. of California,San Diego, La Jolla, CA 92093-0213) Oceansurface processes affecting high-frequency acoustics are reviewed.The generation,propagation, and attenuation of high-frequencysound at andnear the ocean surface is of interestfor manycurrent problems in acousticsand its applications in oceanography.While models of surfacescattering by short surface gravity waves and even shorter gravity-capillary waves can be formulated,the scatterers are not homogeneously distributed on the surface. Nonlinear interactions with longer waves and swell, anddirect forcing by thewind lead to modulationsof thescatterers that are poorly understood. Nonlinear effects may not be weak,with the surface slope becoming infinite in breakingwaves. Breaking waves also generate sound as the entrained air breaks up intosmaller bubbles that radiate as they relax towards their equilibrium shape. The bubbleplumes and clouds scatter and attenuatesound but fieldmeasurements of the acoustic properties of thebubble layer near the surface vary significantly. Bubble cloudsmay align with coherent Langmuir circulations. The surface layers may also be regions of strongtemperature gradients (with concomitantsound-speed gradients), which are brokenup by thermalconvection and breakingwaves. Natural and man-madesurface slicks can suppress the waves and thereby modify both active and passive acoustics. These and other upper oceanprocesses will be reviewed.

1:30

5pUW2.High-frequency sea surface reverberation: An overview.Suzanne T. McDaniel (HC-01Box 62, SpruceCreek, PA 16683) High-frequencyseasurface reverberation is reviewed from an historicalperspective starting with the first comprehensive set of measurementsmade during World War II. Basictheories to predictreverberation due to scatteringfrom resonant subsurface microbubblesand sea surface roughness are alsoreviewed as well as the environmentalinputs to thesetheories: microbubble distributionsand the ocean surface wave-number spectrum. Because resonant microbubbles absorb as well as scatter acoustic energy,a saturation effect is predicted, that is, when the bubble density increases beyond that needed to producesaturation, the backscatterremains constant. The reverberationlevel in thislimit is a uniquefeature of scatteringfrom resonant microbubbles permittinga clear identification ofthis scattering mechanism. Comparison oftheoretical predictions with representative acoustic datademonstrates that reverberation at high grazing angles is due to roughsurface scattering, while at lowergrazing angles it is governedby scattering from resonant microbubbles. Large variations in backscatteringstrength are apparent for measurements performedat the same grazing angle, frequency, and wind speed, with reverberation levels in coastalwaters being an order of magnitudehigher than those in theopen ocean. Although the physical mechanisms responsible forhigh-frequency reverberation arewell understood, the relationship between backscattering variability and environmental factors is not.

1:55

5pUW3.High-frequency forward scattering from the sea surface: Theory and experiments. Peter H. Dahl (Appl.Phys. Lab., Collegeof Oceanand Fishery Sci., Univ. of Washington,Seattle, WA 98105) Intensityand coherence properties ofhigh-frequency sound forward scattered from the sea surface are discussed. Propagation of high-frequencyacoustic energy often involves a sea surface bounce path. In deepwater, and for manygonar acquigition geometries,a single surface bounce may be the best path to the target, because the direct path has faded owing to the sound speed structure.In shallowwater, interaction with boththe sea surface and bottom is oftenthe rule.For frequenciesabove 10 kHz, incoherentsurface scattering in the forwarddirection will usuallydominate over coherent reflection because of thelarge sea surfaceroughness. The mean total energy of thescattered field is reduced by the extinguishing effects of thenear-surface bubble fieldthrough which surface bounce paths must traverse. Coherence properties ofthe scattered field, e.g., spatial and temporal, can

1889 J. Acoust.Soc. Am., Vol. 94, No. 3, Pt. 2, Sept.1993 126thMeeting: Acoustical Society of America 1889 be relatedto the seasurface slope distribution and are alsoinfluenced by near-surfacebubbles. Performance of detectionand classificationsystems will dependon coherenceproperties, and in particulartheir degradationas a functionof sea surface environmentalconditions. Published theories on acousticscattering from the seasurface in the high-frequencylimit are discussed in the contextof recentexperimental measurements of seasurface forward scattering performed by the AppliedPhysics Labo* ratoryin bothinland water (WhidbeyIsland, Puget Sound) and open ocea• conditions (R/P FLIP off Californiacoast).

$pUW4.High-frequeney bistatie ocean surface scattering. Richard Lee Culver (Appl. Res.Lab., PennState Univ., P.O. Box 30, StateCollege, PA 16803) and PeterNeuman (PlanningSystems, Inc., McLean,VA 22102) Understandingand beingable to predicthigh-frequency (10- to 100-kHz) acousticscattering in the oceanfor bistatic geometries(transmitter and receiver not collocated)has become increasingly important in recentyears. For example,bistatic surfaceand bottom scattering must be understoodin orderto predictthe angulardependence or spatialcoherence of acoustic signalswhich have propagated through a sh•lowwater channel. A high-frequencyocean surface scattering experiment conducted by Dahl andJessup in 1992using FLIP utilizedan omnidirectionalsource and a linearray receiver to measurementout-of-plane scatteringat windspeeds up to 7 m/s. Estimatesof low grazingangle bistatic scattering strength have been derived from these measurements,and are shownto comparefavorably to theory developedby S. T. McDaniel. The McDaniel model utilizes composite-roughnesstheory to predictsorfa•e shape effects and includes attenuation and isotropic scatter by subsurfaceresonant bubbles.Bubble scattering is predicted to bethe dominant mechanism at mediumto highwind speeds and low grazing angles, and the FLIP experimentdata offer evidence that thisis the case.

ContributedPapers

2:45 distancefrom the meanofthe roughsurface were used to determinethe peakforward scattered pressure. Composites of thesetypes of scansare 5pUW5. High-frequencyforward scatteringfrom Gaussianspectrum, shownand discussedusing catastrophe theory. The catastrophetheory pressurerelease, corrugated surfaces: Catastrophe theory modeling. simulationis shownto be a valid approximationto the wavefieldfor a K. L. Williams (Appl. Phys. Lab., Univ. of Washington,1013 NE wide rangeof frequencies.[Work supportedby Office of Naval Re- 40th St., Seattle, WA 98105}, J. S. Stroud, and P. L. Marston search.] (WashingtonState Univ., Pullman,WA)

Exactintegral equations for the acousticalpressure scattered from a 3:15 roughpressure release surface can be writtendown and solved numer- ically. However,analytical head way into the problem,gained at the 5pUW7. High-frequencypropagation in a turbulent shallow water expenseof variousapproximations, can lend physicalinsight not easily environment. Danida Dilorio and David M. Farmer (Inst. of Ocean obtainednumerically. This, in part, motivatedthe work to be discussed. Sci., P.O. Box 6000, Sidney,BC V8L 4B2, Canada} In particular,a high-frequencyapproximation will be presentedfor for- ward scatteringfrom Gaussianspectrum, pressure release, corrugated A high-frequency(67-kHz} acousticpropagation experiment con- surfaces.The analysisis most directly applicableto forward scattering ductedin a shallowtidal channelprovides an opportunityfor compar- from an oceansurface dominated by swell. The presentationuses ideas isonof observedacoustical scintillations with availabletheory. The tidal and resultsfrom catastrophetheory [M. V. Berry, "Wavesand Thom's currentensures that the acousticpath runsthrough a turbulentbound- Theorem," Advan. Phys. 25, 1-26 (1976}; P. L. Marston, Phj•sicai ary layer at all times. Analysis of log-amplitude,phase, and phase- .4coustics(Aeademie, New York, 1992), Vol. 21, pp. 1-234] to include differencesignals shows close agreement with the weak scatteringthe- diffraction.Catastrophe theory allowsone to write down the scattered ory of Tatarski usingthe Kolmogorovturbulence model togetherwith pressurein termsof a finiteset of diffractioncatastrophes and stationary the Taylor hypothesisof "frozen" advectedturbulence. By combining phasecontributions. The catastrophetheory results will be comparedto acousticdata with direct measurementof temperatureand salinityfluc- numerical'integration results for an individualrough surface to demon- tuations using in situ sensors,the contributionof turbulent velocity stratetheir validityand the insightthey supply.Both steadystate and fluctuationsto the scintillationsignal is evaluated.The resultsshow that pulsecomparisons will be made.Evidence will be presentedthat this turbulentvelocity fluctuationsrather than temperatureand salinity "high-frequency"approximation is usabledown to frequencieswhere variability are the dominantsource of observedacoustic fluctuations, the wavelengthis twice the rms roughnessof the surface.[Work sup- leadingto estimatesof turbulentenergy dissipation in the range e• 10-5 m2 S-3. portedby Officeof Naval Research.]'

3:00 3:30

5pl_F•6. High-frequency forward seatiering from Gaussian si•tl'um, 5pUW8. Sound propagationthrough a bubble screen. Christopher pressure release, corrugated sarfaees: Experiment and comparison M. Hobbs and Ali R. Kolaini (Natl. Ctr. for Phys. Aeoust., Univ. of with catastrophetheory. J.S. Stroud, P. L. Marston (Phys. Dept., Mississippi,University, MS 38677) Washington grate Univ., Pullman, WA 99164-2814), and K.L. Williams (Univ. of Washington,Seattle, WA) Resultsof a laboratoryexperiment to characterizethe soundprop- agationthrough a bubblescreen are described.A bubblescreen of var- A singlerealization of a Gaussianspectrum surface, rms roughness ions void fractionswas positionedin the middle of an anechoicwater 1.5 cm, correlationlength l0 em was manufacturedout of styrofoam. tank. The cloudwas driven usinga broadbandsource and the aeonstie This surfaceprovided a pressurerelease, corrugated surface for an un- pressurewas measuredon both sides of the layer. The •sults have derwater,forward scattering investigation. Omni-directional source and revealed that there is significantattenuation near the resonancefre- receiver were used in the frequencyrange of 100 to 300 kHz. Short quency of the bubblescontained within the screen.When the source pulseswere used to allow isolation of individual contributionsto the frequencyis nearthat of oneof the "collective-oscillation"frequencies scatteredfield. These individual contributions were then classified using of the screen,sound pressure amplification may occur. In thispaper the catastrophetheory [M. ¾. Berry, "Wavesand Thum's Theorem,"Ad- newfindings corresponding to the collectivemode amplification, high- van. Phys. 25, 1-26 (1976}; P. L. Marston, Physical,4caustics (Aca- frequencyattenuation, as a functionof the screen'sphysical properties demic, New York, 1992), Vol. 21, pp. 1-234]. Scansat a constant are discussed.[Work supportedby ONR.]

1890 J. Acoust.Soc. Am., Vol. 94, No.3, Pt.2, Sept.1993 126thMeeting: Acoustical Society of America 1890 3:45 large-amplitude,low-frequency sound. The resultsof laboratorystudy 5pUW9. Low-frequencyacoustic emissionsby impacting transient of the noiseproduced by this processwere reportedpreviously by Ko- cylindrical water jets in fresh and salt water. Ali R. Kolaini (Natl. laini et at [J. Acoust.Soc. Am. 89, 2452-2455(1991)l. In thispresen- Ctr. for Phys.Acoust., Univ. of Mississippi,MS 38677), RonaldA. tation,a fieldstudy of noiseproduced by thisprocess in bothfresh water Roy (Univ. of Washington,Seattle, WA 98105), and David L. (Lake Washington)and saltwater (the PugetSound) will be described. Gardner (NOAA, PMEL, Seattle, WA 98115) Studiesof acousticemissions from transientbubble plumes as a function The impactof a jet of wateronto a still water surfaceresults in the of cylinderparameters will be described,with specificattention devoted entrainmentof large amountsof air and the eventualformation of a to a comparisonof resultsobtained in salt and fresh water. The mea- bubbleplume. The denselypopulated bubble plumes were generated by surements indicate that there is a correlation between the acoustic in- droppinga fixed volumeof water, held in a cylindricalcontainer, onto tensityradiated from bubbleplumes and the total potentialenergy of the a still-watersurface. The detachedbubble plume, which is roughly waterjet. [Work supportedby ONR.] sphericalin shape,undergoes volume pulsationsand radiatesrelatively

FRIDAY AFTERNOON, 8 OCTOBER 1993 (TO BE ANNOUNCED) ROOM, 1:00 TO 2:30 P.M.

Session5pAA

Architectural Acoustics:Vern O. KnudsenDistinguished Lecture

David Lubman, Chair David Lubman & Associates,Westminister, California 92683

Chair's Introduefio•l:00

lnoited Paper

1:05

5pAAI. Qmmtifying musical acousticsthrough audibiliOd.David H. Griesinger (Lexicon, 100 Beaver St., Waltham, MA 02154}

This paperproposes a setof measuresof musicalacoustics derived from a studyof binauralhearing and speechperception. The measuresare testedon analyzingdata from unoccupiedand occupiedhalls, data from severalhalls which include electron- ically variableacoustics capable of a wide rangeof adjustment,and data from a binauralsynthesizer of hall acoustics.The new measuresinclude the 500-ms reverberantlevel (L500), early (0--60 ms) reverb time (ERTL middle (0.1-0.5 s} reverb time (MRT}, late (0.5+} reverbtime (LRT}, early binauralfraction (EBF), and middle binauralfraction (MBF). L500, a measure of reverberantlevel, is relatedto early decaytime (EDT). OptimumL500 is foundto be high in the rangeof musicalfunda- mentals,and low in the regionof maximumspeech information. ERT is in parta measureof the Iocalizabilityof the sound,which is relatedto its clarity.MRT is particularlysignificant whenever the decaycurve is not a simpleexponential. It is foundthat when MRT is muchlonger that ERT the soundcan be both clearand reverberantat the sametime. The binauralmeasures are found to be similar to IACC, but have advantagesat frequenciesbelow 300 Hz. Someimplications of this researchon optimum hall shapeand surfacetreatment are discussed.

2:00 DISCUSSION

1891 J. Acoust. Soc. Am., VoL 94, No. 3, Pt. 2, Sept. 1993 126th Meeting: Acoustical Society of America 1891