PostnasalVoicing BruceHayesTanyaStivers UniversityofCalifornia,LosAngeles Draft:June2000 Abstract Manyoftheworld’slanguagesdisplayaphoneticpatternwherebyobstruentsappearas voicedwhenfollowinganasalconsonant.Thisarticleproposesaphoneticmechanismthatfavors postnasalvoicing.Themechanismisbasedontwoeffects,whichsometimesreinforce,and sometimescontradicteachanother.Oneeffectis“nasalleak,”theleakageofairthroughanearly closedvelarportduringthecoarticulatoryperiodbetweenanoralandanasalsegment.Theother is“velarpumping,”whicharisesfromtheverticalmotionofaclosedvelum. Themainpurposeofthearticleistotestthisproposal,intwoways.First,acomputational simulationofvocaltractaerodynamicsisusedtoshowthat,underarangeofplausible assumptions,themechanismspositedwouldindeedproduceasubstantialphoneticeffectinthe directionofpostnasalvoicing.Second,measurementswerecarriedoutoftheproductionsof5 nativespeakersofEnglishproducingstopsinacontrolledcomparisoncontext(postnasal/ ¡ ¡ [ tam___ ]vs./postoral[ ta ¢ ___p ]).Theresultsindicatethatpostnasalvoicingpresentasa quantitativeeffecteveninalanguagewhosephonologylacksaqualitativepostnasalvoicing process. 1. Introduction Manyoftheworld’slanguagesdisplayaphoneticpatternwherebyobstruentsappearas voicedwhenfollowinganasalconsonant(Ferguson1975).Forexample,inWembawemba (Hercus1986),theresinglephonemicseriesofstops,whichnormallyappearsasvoiceless(1)a, butisvoicedpostnasally(1)b: (1)a. /taka/ [ tak £ ] ‘tohit’ £ /milpa/ [ m¤ lp ] ‘totwist’ b. /yantin/ [ yand ¤ n] ‘me’ /panpar/ [ panb £ r] ‘shovel’ HayesandStivers APhoneticAccountofPostnasalVoicing p.2 Thepatterniswidespread;herearesomelanguagesthatshowpostnasalvoicing;welistalso thepagesfromoursourcematerialwherepostnasalvoicingisdiscussed. (2)Arusa(Levergood1987,204) EasternArmenian(Allen1951,202-3) Japanese(ItoandMester1986) ModernGreekdialects(Newton1972) Waorani(SaintandPike1962,xxx) WesternDesertLanguage(Douglas1958,3) Zoque(Wonderly1951,xxx) ManyofthelistingsinwerelocatedbyLocke(1983),whocheckedthe197languagesofthe StanfordUniversalsProject,andfound15withspecificallypost-nasalvoicing.Totheextentthat theStanfordsampleisrepresentative,itisplausibletoconcludethatpostnasalvoicingisfoundin anon-negligeablefractionoftheworld’slanguages. Postnasalvoicinghasbeenthesubjectofrecenttheoreticaldiscussioninphonology.Itoet al.(1995)treattheprocessasakindofassimilation,wherebythevoicingofthenasalperseverates (spreads)tothefollowingobstruent,despitethefactthatvoicingonnasalsintherelevant languagesischaracteristicallynotphonologicallycontrastive.Theyproposeaningenious mechanismforpermittingsuchassimilationswhileretainingunderspecifiedphonological representations. Pater(1995,1996)findsfaultwiththeItoetal.account.Henotes,amongotherthings,that Itoetal.’stheorywouldpredictthatobstruentsprecedingnasalswouldbelikelytobevoicedas well.Infact,inthedataPaterexamines(aswellasintheexampleswehaveseen),thisdoesnot occur.1Patersuggeststhatthebasisofpostnasalvoicingislikelytobephonetic,andprovides someoutlinesuggestionsalongtheselines. Thepurposeofthisarticleistoexplorethephoneticsofpostnasalvoicingingreaterdetail. Wediscusstwopossiblemechanismsthat,incombination,mightbeexpectedtoyieldthe typologicalpatternjustnoted.Thearticlehastwoparts.First,wewilltesttheproposed mechanismsbymeansofaerodynamicmodeling.Second,weattempttoestablishthataphonetic tendencytowardpostnasalvoicingispresenteveninalanguage(AmericanEnglish)thatlack postnasalvoicinginitsphonology.Wewillsuggestthattogether,ourresultssupportaviewof phonologicalpostnasalvoicingthatistiedfairlydirectlytoitsphoneticorigins. 1Obstruentsareoccasionallyvoicedbeforenasals,asinxxx,butinallsuchexampleswehaveseen, theyarevoicedbeforeothervoicedsonorants(e.g.,liquids)aswell.Thissuggeststhatinsuchcases,the casualmechanismforvoicingisnotcloselyconnectedtonasality.Incontrast,forthepost-nasalcases, thereareafairnumberofinstancesinwhichitisonlynasalconsonantsthatcaninducevoicing. HayesandStivers APhoneticAccountofPostnasalVoicing p.3 2. ReviewoftheMechanismsofObstruentVoicing TheconditionsunderwhichobstruentswillbevoicedhavebeenexaminedbyWarren(1976), Ohala(19xx),Westbury(1979,1983),WestburyandKeating(19xx),amongothers.According toWestbury(19xx,1),“voicingobtainsinspeechwhenthevocalfoldsareproperlyadductedand tensed,andasufficienttransglottalairflowispresent.Theabsenceofvoicingobtains,by contrast,whenatleastoneoftheseconditionsisnotmet.” Inobstruents,themaintenanceoftransglottalairflowisinparticularperil,sincetheexitofair fromtheoralchamberispartiallyorfullyblocked.Thisblockageleadstoarapidbuildupof supraglottalairpressure,hencetothecessationoftransglottalairflowandofvoicing.Voicingis prolongedifthebuildupisavertedorsufficientlydelayed.Anumberoffactorsdetermine whetherthiswillhappen: PharyngealExpansion.Voicingisfavoredifthepharynxisexpandedduringthecourseof anobstruent.Thisisbecausesuchexpansionpermitsmoreairtopassthroughtheglottis,sothat thetimeduringwhichthereissufficientpressuredropacrosstheglottisisextended.Expansion ofthepharynxcantakeplacebyappropriatemovementsofthetongueroot,thelarynx,andthe pharyngealwalls(Westburyxxx). SubglottalPressure.Wheresubglottalpressureislower,thepressuredropacrossthe glottisisreduced,anddevoicingwillbefavored.Typically,subglottalpressurerespondsto utteranceposition,beingfairlyconstantutterance-mediallybutloweratutterancebeginningsand especiallyendings.Thisgivesrisetoatendencyforlanguagestoemployonlyvoiceless obstruentsinutterance-final(andtoalesserextent)utterance-initialposition(Westburyand Keating1986). VocalFoldAdjustments.Abductionofthevocalfoldswillingeneralleadmorerapidlyto acessationofvoicing.Thisisdueinparttothelesserpropensityofthevocalfoldstovibrate whenabducted,andinpartobstruents)tothefactthatabductedvocalfoldswillpermitafaster buildupofairpressureintheoralcavityandthusblockvoicingsooner.Itisprobablyforthis reasonthataspiratedstopsaretypicallyvoiceless;voicedaspiratesrequireparticularadditional mechanisms(Rothenberg1968);(Dixit19xxUCLAWPP)topreservevoicing.HalleandStevens (1971),basedonacomputationalmodelofthevocalfolds,arguethatastiffeningofthevocal cordswilllikewisediscouragevoicing.[xxxread] PlaceofArticulation.Placesofarticulationnearerthefrontofthemouthprovidelarger surfacesofsofttissueinthevocaltractwalls,theyieldingofwhichpermitsmoreairtobe accommodatedsupralaryngeallybeforevoicingwouldbesuppressed.[xxxrefs.] Velum-RelatedFactors.Therearetwofactorsinvoicingcontrolthatinvolvethevelum andthuswillplayacrucialroleinthediscussionhere. (a)NasalLeak.Atthehighestrangeofpossiblevelumheights,thevelarportisfullyclosed, andanylinguisticsoundresultingwillbefullynon-nasal.Whenthevelumissufficientlylowered, HayesandStivers APhoneticAccountofPostnasalVoicing p.4 thevelarportissufficientlyopensothatanylinguisticsoundproducedwillbefullynasal.In addition,thereareintermediatevelumpositionsinwhichair“leaks”throughthevelarport,but thereisnosignificantacousticcouplingbetweenthenasalandoralcavities.Asoundmadewith “nasalleak”willsoundoral,2andpresumablyshouldbeclassifiedphonologicallyasoral. Rothenberg(1968),and,tentatively,KentandMoll(1969)xxxhaveclaimedthatnasalleakisa mechanismusedbysomespeakersinmaintainingvoicinginobstruents.Ohala(1983xxx) suggeststhatnasalleakmaybethelinkwherebycertainvoicedstopshavehistoricallyevolved intoprenasalizedstopsornasal+stopsequences,inwhichthenasalityhasbecomeacoustically patent.Theinteractionofnasalleakwithnasalcoarticulationisdiscussedfurtherbelow. (b)VelumRaising.Bell-Berti(1975)andBell-BertiandHirose(1975)haveobservedan additionalfactorthatcaninfluencethevoicingofaconsonant.Tounderstandthis,onemust consideranimportantaspectofvelaranatomy,describedasfollowsbyBell-Berti(19xx,video; italicsours):“Thereisawell-establishedrelationshipbetweenthesizeoftheopenvelarportand thepositionofthevelum.Inaddition,though,tovaryingwithportarea,velarpositionalsovaries whentheportiscompletelyclosed.Theseadjustmentsresultfromtheanatomicalrelationship betweenthevelumandthelevatorpalatinimuscle.Sincethemuscle’ssuperiorattachmentlies wellabovethelevelatwhichportclosureiscomplete,increasingcontractionofthismuscle continuestoraisethevelumevenafterclosurehasoccurred.”Ourinspectionofvarious cinefluorographicfilmskeptintheUCLAPhoneticsLaboratoryconfirmsBell-Berti’s observations,atleastinsofarassuchinspectioncandeterminethepointofvelarclosure(Bjørk 1961). ThemovementsthatBell-Bertidescribesareinprinciplecapableofchangingthevolumeof theoralcavity,increasingitasthevelumrisesanddecreasingitasthevelumfalls.Sincechanges inoralcavitysizeinfluencevoicing,thismechanismisthusasecondpotentiallink(afternasal leak)betweenvoicingandvelummovement. Afactorthatincreasesthelikelihoodofvelumraisinginfluencingvoicingisthatobstruents typicallyhavethehighestvelumpositionsofallsegments,usuallyhigherthanoralsonorants (Bell-Berti19xx).Thereasonforthispatternisnotknown,butthepatternisapparentlyrobust. Theexperimentaldataonwhetherraisingoftheclosedvelumisactuallyusedbyspeakersto maintainobstruentvoicingiscontradictory.Studiesinwhichvoicinginobstruentswasapparently facilitatedbyvelumraisingincludePerkell(1969;discussedinBell-Berti19xx),Bell-Berti(19xx; xx),Bell-Bertietal.(1979)andHiroto,HiranoandUmeno(1963).However,equalorhigher velumpositionsforvoicelessobstruentshavebeenobservedbyWestbury(1979,1983)andby xxx.Ourinteresthere,however,concernsnotwhethervelumraisingisalwaysusedasa mechanismofvoicingcontrol(itprobablyisnot),butratherthedistinctissueofwhether,given velumraising,voicingwillbefacilitated.Inthecontexttobeconsideredbelow,velumraising maybetakenasgiven,asitiscoarticulatoryinorigin. ¡ ¡ ¡ ¡ ¡