Patents: Digital Hearing Aids and Related Devices

Compiled by Helen Nowolarski, programnlable nlemory (15) can be changed or Tcc.hnic.nl lufi)rnlcxtior~Spcc icrlist modified by operation of a switch (19) which can be manually user-operated or automatically, for The following is a selected list of patents on digital example by measuring stapedius reflexes. After hearing aids and related devices as found in the setting or changing the transfer frrnction in the pate~ltdatabase of BRS (database vendor). The programmable memory (15), the normal program patent database is produced by the U.S. Patent & of the digital data processor - which can be of Trademark Ofice of the U.S. Department of Com- standard construction - is engaged by switch-over merce and includes patents from 1975 to the present. by a user-controlled transfer switch (18). Patents in this database are classified by number, US 447 1 171. SEP l 1, 1984. Application No. 466,840; title, and inventor, but not by subject. However, a Filed FEB 16, 1983. subject search was required for our purposes, and terms related to digital hearing aicls, such as audi- Hearing Aid with Digital Processing for Correlation ometric, audiometer, processor, filter, speech, com- of Signals from P1usal Microphones, Dynamic Range puter, and digital were used to retrieve the citations. Control, or Filtering Using an Erasable Memory: The names of the researchers who contributed to Mosec-Ludwig-M. this issue of the Jourrzal also were included in the In an illustrated embodiment a behind-the-ear search. hearing aid includes a microphone, an amplifier- Each entry presented below includes the name of low pass filter circuit, an analog to digital con- the device, the inventor (last name then first name, verter, a digital integrated circuit arithmetic and separated by a hyphen), and an abstract describing logic unit for implementing a n-th order transfer the device and its intended use. Following the function in the 2, clomain, a digital to analog abstract is a line of identifiers: the U.S. patent converter and an output transducer, for producing number, the date the patent was issued, the number the desired sound response. A memory multi- given the inventor's application for a patent, and plexer is provided for loading of the multiplier the date the application was filed with the U.S. coefficients necessary to adapt the tl-ansfer func- Patent & Trademark Office. tion circuit to essentially any class of hearing deficiency into an erasable programmable read only melxlory (EPROM). The structure is such Digital Wearing Aid and Method: Kopke-Wolfgang, that the coefficient lnemory may be loaded after Wiener-Peter, Maas-Rainer. Eggerl-Albert. Gotze- the standard universal hearing aid has been corn- Gerd-Wolfgang. pletely assembled, and indeed the hearing aid may To match the operation of a digital hear-ing aid be reprogrammed as needed after a period of use, directly to user requirements, and to reprogram essentially without disassembly. the hearing aid as the hearing aid and/or user US 418741 3. FEE3 05, 1980. Application No. 894,348; response characteristics change, a digital data Filed APR 07, 1978. processing element (12) processing digitized audio signals is connected to a programmable memory Differential Hearing Aid with Programmable Fre- such as an EEPROM or an EAIiAM which stores quency Response: Slavin-Martin-J. predetermined li-equency vs. amplitude transfer A difkrential input hearing aid with a programm- fu~~ctionsin accordance with user requirements able frequency response provides the hard of or preference andlor hearing aid operation. Ad- hearing with the capability to listen to individual ditionally, a memory (ROM 17) is provided storing conversations in the midst of high ambient back- a test program which causes the digital processor ground noise, and to have the li-equency response to generate test li-equencies or tones at varying of the hearing aid tailored to the individual user amplitudes, so that the transfer function in the by progralnmlng the desired response character- Journal of Rehabilitation Research and Development Vol. 24 No. 4 Fall 1987

istics into the hearing aid by digital signals. The digital to analog converters may be constructed audio inputs of two microphones are applied to a on the same monolithic semiconductor chip. subtractive circuit with the balance of the inputs US 4396806. AUC 02, 1983. Application No. 198,677; being controllable. Digitally controlled band pass Filed OCT 20, 1980. filters with selectable band and selectable level of amplification are provided. hplanhble Electronic Hearing Aid: Kissiah-Jr-Adam- US 4622440. NOV l 1, 1986. Application No. 599,137; M. Filed APR 11, 1984. An electronic hearing aid device for enabling persons having loss of hearing due to a nonfunc- Class D Hearing Aid Amplifier: Killion-Mead-6. tioning malfunctioning inner ear (Cochlea), but A subminiature power amplifier for hearing aids have having a responsive auditory (acoustic, or cor-tfigured to be completely self-contained and fit eighth cranial) nerve, to hear by way of an within the user's ear features a Class D arnplifier electronic device including a microphone for re- stage. By configuring all signal elements as digital ceiving audio signals connected to an amplifier units, circuit balance is readily maintained. A for converting the audio signal into an analog substantial economy of battery drain is achieved voltage signal. The analog voltage signal is filtered while preserving a low value of distortion at low by a series of filter networks which separate the signal levels. Oscillator frequellcy is governed by analog voltage signal into a plurality of frequency a single resistance element, The amplifier and an component signals each having a predetermined optional efficiency-improving inductor can be ac- frequency range within the audio $pectrum. The commodated entirely within the residl~alvolume component analog voltage signals are then con- of the motor chanlber of a state-of-the-art ear- verted into digital pulse signals having the same phone housing. frequency as the component voltage +gal, which US 4592087. MAY 27, 1986. Application No. 559,386; are fed to the auditory nerve by way of implanted Filed DEC 08, 1983. platinium platin~im(or other) wires, wherein the digital pulse signals more accurately simulate the Hearing Aid Amplifier: Anderson-Jared-A. llatural sound signals tr-anrmitted to the b1.ai11 for A general purpose hearing aid amplifier is pro- interpretation. grammably adaptable to the prescription require- US REISSUE 3103I. SEP 14, 1982. Application ments of the hearing imp;iired. The heziring aid No. 102,377; Filed DEG 1 1, 1979. amplifier comprises a bank of bandpass-restricted channels, each channel having a voltage -con- Method and Apparatus for Measusinag Attack and trolled inp~ltamplifier, a voltage-controlled com- Release Times sf Hearing Aids: Sopher-Joshua-E, pressor, and a voltage-col~lrolledoutput amplifier At the option of an operator, the attack or relea5e for shaping the gain, attack and dclay character- time of a hearing aid is ar~tor~~aticadlymeastarecl, istics of the selectecI channel. 'Tile bank is fed and the llneasurenlent displayed in ~nllliseconds through a fixed high-pars filter from a microphone on a digital readout. A test tone signal of co~ista~~t input, and a nlixed output drives a power amplifier frequency is successively cycled between rela- for an output trar~sducersuch ax a hearing aid tively low and high power levelc. During the first speaker. The amplifier is programmably adaptable cycle of the test signal a ,ample is t;tken and through the use of a rnsnolithic programmable stored which is representative of the steady slate switch array using, for example, cemiconductor response of the hearillg aid under test; and during ft~seablelir-rk technology to preset digital-lo-analog the second cycle a measurement i\ automatically converters voltage controllable levels of the am- made of the time required for the outp~ttof the plifiers and cornpressors of each chanr~elaccord- hearing aid to settle to wi"iin a predetermined ing to a digital control input. The rnonolitl~icswitch recovery range about the stored sample sigrral. array is coupled to the programmable amplifiers US 41 96 864. MAR 04, 1980. Application No. 936735; through digital to analog converters which estab- Filed AUG 25. 1978. lish the programming voltages for the amplifiers and compressors. The monolithic switch array 297

Bibliographic Section: Patents Relating to Digital Hearing Aids

Audiometric Testing, Analyzing, and Recording Ap- number of tone bursts varied randomly from one paratus and Method: Besserman-Richard. to four in each test sequence and automatically An audiometric testing system containing a pro- decreased in level. The subject is provided with cessor and programmable analog circuitry for a response panel containing pushbuttons labelled controlling frequency and intensity of audiometric one through four. The subject's bearing threshold test tones communicates with a remote data proc- is then determined from his pushbutton responses essing system via a communications link. The to his correct burrst tone counts. remote data processing system stores prior audi- US 3970785. JUL 20, 1976. P.pplication No. 577,133; ometric records for a large number of subjects. Filed MAY 13, 1975. Each day, the audiometric records of a number of selected persons are transmitted from the re- Automatic Gail1 Selector for a Noise Suppression mote data processing system to a memory of the System: Bortlh-David-E, Gerson-Ira-A. Smanski- audiometric testing system in response to identi- Philip-J. Vilmur-Richard-J. fication numbers entered by an operator. The An automatic gain selector is disclosed for use audiometric responses of each person to patterns with a noise suppression system which performs of sounds of varying frequencies and intensities speech quality enhancement upon a noisy speech are determined. The varying frequencies and in- signal available at the input to generate a noise- tensities are determined by a bracketing subrou- suppressed speech signal at the output by spectral tine of an algorithm stored in and executed by a gain modification. The channel gain controller processor of the audiometric testing system. A (240) of the present invention produces a modifi- person's responses to such test tones are utilized cation signal (245), comprised of individual chan- by the bracketing subroutine to determine his nel gain values, for application to a channel gain threshold levels at the respective frequencies for modifier (250). A particular gain table set is au- each ear. The algorithm automatically computes tomatically selected from one of a plurality of the pure tone averages for each ear from the gain tables (450) by a selector switch (470) and a threshold levels at a plurality of predetermined noise level quantizer (440) in response to a multi- frequencies. The algorithm also automatically channel noise parameter, such as the overall computes the binaural hearing impairment based average background noise level of the input signal. on test results from prior testing of the person. Then the individual channel gain values (455) are Any significant shift in threshold is determined obtained from the particular gain table set in by comparison with the prior test results. The response to the individual channel signal-to-noise a~~diometrictesting system includes a printer which ratio estimate (235). Hence, each individual chan- prints the persons' complete hearing test record, nel gain value is selected as a function of (a) the including relevant identifying information, present channel number, (b) the current channel SNR test results, pure tone averages, binaural hearing estimate, and (c) the overall average background impairment, significant threshold shifts, and a noise level. The automatic gain selector further recommended time for the next testing. After all includes a gain smoothing filter (460) for smoothing persons have been tested for the day, their updated these noise suppression gain factors on a per- audiometric records are transmitted via the com- sample basis thereby improving noise Mutter per- munications link to the remote data processing formance caused by step discontinuities in frame- system. to-frame gain changes. US 4284847. AUG 18, 1981. Application No. 119,818; US 4630305. DEC 16,1986. Application No. 750,941 ; Filed FEB 08, 1980. Filed JUL 01, 1985.

Tone Count Audiometric Computer: Meyer-Charles- Amplifier Arrangement for Acoustic Signals, Pro- R. vided with Means for Suppressing (undesired) Spu- A hearing threshold level measuring apparatus for rious Signals: Admiraal-Daniel-J-H. Lopes -Car- automatically determining testing hearing level in dozo-Benjamin. each ear and processing the test scores for either An amplifier for acoustic signals provided with manual or automatic readout. A predetermined means for suppressing undersired acoustic feed- Journal of Rehabilitation Research and Development Vol. 24 No. 4 Fall 1989

back signals in a rapid manner. The amplifier is applied in parallel to a noise-analysis circuit includes a high-pass filter which separates a part and a noise-reduction circuit, each of which com- of the signal to be amplified to obtain a control prises a plurality of bandpass filters covering the signal for reducing the gain of the amplifier when range of frcqucncics associated with the infor- an acoustic feedback signal is detected. The output mation. The absolrite value, or a frlnction thereof, of the high-pass filter is connected lo a periodicity of the output of each bandpass filter in the noise- detector, e.g. a single peak detector, which dis- analysis circuit is prodriced and smoothed. The criminates between an acoustic feedback signal presence of near-stationary noise in the input having a regular periodicity and a signal having signal is determined by examining the nature of an irregular character, such as noise or speech. the smoothed signal in each band assuming noise The control signal is derived frorn the output of has a frequency spectrum which does not vary the periodicity detector. with time or varies only within a narrow range US 4525856. JUN 25, 1985. Application No. 006,144. over a predetermined period of time with respect Filed JAN 24, 1979. to the spectral parameters of the information signal. If noise is detected, the noise-analysis Combination Speech Synthesis and Recognition Ap- circuit identifies spectral parameters of the infor- paratus: Monklick-Terry . Skoge-Klaus. Vetter- mation and/or noise in each band using the srnoothecl David-6, Ahrens-Paul-R. signal therein. In the preferred embodiment of the A reconfigurable lattice filter is employed to permit invention, the bandpass filters of the noise-reduc- the same circuitry to function as a speech syn- tion circuit have gain elements that are adjusted thesizer and as a speech analy~eror recognizer. in accordance with the identified pararnelers to The lattice filter can be configured both as an all- minimize, under some continuous minimization pole filter (for synthesis) and as an all-zero filter criterion, the effect of the noise in the input signal (for analysis), with the choice being determined thus enhancing intelligibility of the information by the state of an analysisisynthesis signal (i. e. therein. Minimization can be such that the gain- mode control signal) provided thereto. The con- to-parameter relationships are similar to those in nections betweer1 various elements in the circuitry Weiner or Kalman filtering theory with a-priori are controlled by the analysisisynthesis signal, knowledge of the noise, or of the noise and also. In synthesis mode, partial correlation coef- information, except that In this case, a-priori ficients are supplied to the filter from a micropro- knowledge of the noise is acquired via identifi- cessor. The filter is excited by a one of a number cation and is not preassumed. of stored patterns si~nulatinga glottal pulse for US 4 185 168. JAN 22, 1980. Application No. 866,938; voiced sou~ldsand by a pseudo-randon? noise Filed JAN 04, 1978. generator for unvoiced sounds. In analysis mode, appropriate feedback control paths are enabled Processor Controlled Ear Responsive Hearing Aid so as to provide to the filter coefficients which and Method: C:ilman-Samuel. change in response to changes in the input speech A processor controlled ear responsive Ilearing aid waveform. Coefficient values thus determined are for the ear of a hearing i~npairedindividual and averaged over fixed intervals and 5uccessions of method for operating a hearing aid. The lnptlt such averaged coefficient sets prod~lcereprescn- from the microphone is amplified and split into a tations of words or phrases whicli can then be plurality of band-pass channels each having a used for speech recognition. frequency range of approximately one-third oc- US 4520499. MAY 28, 1985. Application No. 392,309; tave. Each channel has an amplifier that i%con- Filed JUN 25, 1982. trolled by the proce$\or. The processor- receives control 4ignals from a feedback microphone lo- Method and Means for Adaptiveny Filtering Near- cated in the ear canal and u4es the control signals Stationary Noise from an Information Bearing to develop a spectrum of the act~iallound pre\\ure Signal: Graupe-Daniel, Causey-G-Donald, levels by fi-equency at the earclrum. The proce\\or- An input signit1 containing Information such as cornparer averages of the actual \ouncl pres5rrre speech or music as well a, near-stationary noise levels to the desircd levels for each channel and 299 Bibliographic Section: Patents Relating to Digital Hearing Aids

for- the overall output according to a predeter- Programmable Signall Processing Device: Mansgold- mined set of instruc"rons and controls the channel Stephan, Leijon-Arne, Israelsson-Bjornmnm amplifiers and an output an~plifierto produce the The invention refers to a progran~mablesignal desired sound pressure levels for each frequency processing device ~nainlyintended fo'or flearing in the ear canal. aids and of the kind which include an electronically US 4596902.J liN 24, 1986. Application No. 755,467; controlled signal processor. Hearing aids for per- Filed JUL 16, 1985. sons having ia~~pairedhearing are normally ad- justed for only one frecluency response and are Device for the Compensation of IIearing Tmpairmemts: adapted lo alnplify the frequencies which the Steeger-Geshard. patient has difficulties to hear. At different sound An exemplary embodiment includes a plurality of environments as for example conlversalions with parallel signal channels cocrpled with a signal input disturbing background sounds, normal conversa- transducer, such as a microphone or induction tion in quiet environments or at lectures, the coil. Each of the signal cl~annelsincludes a re- conditions of listening are different. Up to now spective bandpass filter for selection of a different this problem has not been solved satisfiictorily frequency band, a controllecl-gain amplifier, con- for hearir~gaids. With the present invention a "coiled by a volume control potentiometer, circuits number of different signal processes, can easily for not?linear signal processing, and a barldpass be selected lo suit different sound situations ;ur- filter for the redelctior~of distortion components tomatically or by the user himself. This is accorn- caused by the nor^r-linear processirlg circuits. A plishecl thereby that a memory (6) is arranged to srlrnlning amplifier conlbines the signal cornpo- store irafor-rmationld~~tafor at least two unique nents froan all channels and is connected via an cignal processec, adjusted to di6ferent 5o~lnden- amplifier to ara output Ggnal transdrrcer. Space vironmer~tsllisteningsitu;rtions aaad that a coa-rtrol requirements and power- corrscan-rption are reduced unit (5). lnax~~lalor automatic, is arraraged to in such a m~LIi-chiln~~elproces~ing arrangement transmit informationldata, for one of the unlqcre by irnplenrenling all of the filler4 ac sampled-data signal processes, From the mernory (6) to the analog circtxrts. As a rewlt hearing aids are pro- signal processor (4), to bring about one signal vidcd which can be worn on the head, e.g. behincl proce\s 21djusted to a particular sound environ- the car. menlllislenirrg situation. LJS 4508940. APRO2,1985. Applrcation No. 400,413; BJS 442511.81. JAN 10, 1984. Application No. 368,456; Filecl JUL 21, 1982. Filed APR 14, 1982. Computerized Awdiormeter: SLavira-Martin-J. A computerized a~~drometeris provided with at Signal Processing Apparatus: Adelman-Roger-AA least one head set, a conC1-01 switckr, a tone A generalizeti signal processing device for use as gener.ator for providing a plrrrality of sequential a hearing aid generates and moclifies signals rep- tones of different frequencies and amplification., resentative of cacousIXc patterns in a physiologi- to oat least one head set, and a central processing cally compatible xnanner which e~xablesperlons unit for receiving data representative of the re- 5rrffering from various auditory pathologies to lponse to the test of' the person being te\ted ;I\ recogl~izesorlnd palderns lnclrlding I-ruman speech. reflected by the operation of the control switch. kiS4.4.19544.DEC' Oh, 1983. App1ication-r No. 371,584; The central processing errlit is adapted lo analyze Filzd APR 26, 1982. the test data and prodrxce :a progrikm representi~tive of the correction required by the per\or~beir~g Generalized Signla] Processing Hearing Aid: Adelman- te5ted. 'l'he audiometer is provided with ;r pro- Roger- A, gramming ocrtput ~tdaptedfor corrpling to a hearing A gener-alized signal processing devrce for use as aid for progr~irnminga hearing aid by applying the a hearing aid generates and n~odifiessignals rep- program developed by the central processing unit resenlativc of acoer\tic patterrrs in a pl-rysiologi- to the hearing aid. cally compatible mmner which cnables persons US 4489610. DEC 25, 19884. Application No. 59g7152; 4ufL"ering l'r-orn varaoers auditory pa"lc>logie\ to Filed APR 1 1, 1984. recognize sound patterns lncludilag human speech. Journal of Rehabilitation Research and Development Vol. 24 No. 4 Fall 1987

US 4366349. DEC 28,1982. Application No. 144,395; controls. The hearing aid selected is of a type Filed APR 28, 1980. which may have one or more adjustable filter networks and a maximum power output adjust- Hearing Aids, Signal Supplying Apparatus, Systems ment or any combination of one or more of these. for Compensating Hearing Deficiencies, and Meth- Whatever adjustable controls the hearing aid may ods: Engebretson-A-Maynard. Morley-Robert-E Jr. have for its filters or for maximum power output Popelka-Gerald-R. are then adjusted by reference to the reciprocal A hearing aid including a microphone for gener- gain values so that the audio response curve of ating an electrical output from sounds external to the hearing aid closely approximates that of the a user of the hearing aid, an electrically driven master hearing aid. receiver for emitting sound into the ear of the US 3989904. NOV 02, 1976. Application No. 537,066; user of the hearing aid, and circuitry for driving Filed DEC 30, 1974. the receiver. The circuitry drives the receiver in a self-generating mode activated by a first set of Noise Suppression System: Borth-David-E. Gerson- signals supplied externally of the hearing aid to Ira-A. Vilmur-Richard-J. cause the receiver to emit sound having at least An improved noise suppression system (400) is one parameter controlled by the first set of exter- disclosed which performs speech quality enhance- nally supplied signals and then drives the receiver ment upon speech-plus-noise signal available at in a filtering mode, activated by a second set of the input (205) to generate a clean speech signal signals supplied externally of the hearing aid, with at the output (265) by spectral gain modification. the output of the external microphone filtered The noise suppression system of the present according to filter parameters established by the invention includes a background noise estimator second set of the externally supplied signals. Other (420) which generates and stores an estimate of forms of the hearing aid, apparatus for supplying the background noise power spectral density based the sets of signals to the hearing aid in a total upon pre-processed speech (219, as determined system, and methods of operation are also de- by the detected minima of the post-processed scribed. speech energy level. This post-processed speech US 4548082. OCT 22,1985. Application No. 645,004; (255) may be obtained directly from the output of Filed AUG 28, 1984. the noise suppression system, or may be simulated by multiplying the pre-processed speech energy (225) by the channel gain values of the modification Method and Apparatus for Setting an Aural Prosthesis signal (245). This technique of implementing post- to Provide Specific Auditory Deficiency Correc- processed signal to generate the background noise Lions: Rohrer-John-S. Blackledge-Vernon-0. Apparatus for setting or adjusting an aural pros- estimate (325) provides a more accurate measure- thesis, such as a hearing aid, in order to provide ment of the background noise energy since it is compensatory amplification or attenuation for aur- based upon much cleaner speech signal. As a ally handicapped persons such that the prosthesis result, the present invention perlorms acoustic compensates for the specific auditory deficiencies noise suppression in high ambient noise back- grounds with significantly less voice quality deg- fo that person. The apparatus includes a master radation. bearing aid having one or more adjustable gain US 4628529. DEC 09,1986. Application No. 750,942; controls for determining the person's preferred Filed JUL 01, 1985. word discrimination levels for a plurality of fre- quency bands. As the master hearing aid is set at the person's preferred level for each separate Audiometer: Voss-Rainer. band, a reciprocal control coupled to each master An audiometer that automatically produces test control is adjusted at the same time. A hearing tones of predetermined duration whose frequency aid is then selected having an acuity deficiency and level are changed in accordance with a pro- correction characteristic generally similar to that gramme. The persons being examined actuate a determined by the previous test information, and switch or the like each time that a test tone is that hearing aid is coupled to the reciprocal gain perceived and the parameters of said test tone 301 Bibliographic Section: Patents Relating to Digital Hearing Aids

(frequency and level) are stored in a memory. operational safeguards which assist the audiome- Thus, evaluation becomes very simple. Further- ter operator in the desired performance of the more, steps have been taken to measure the audiometric testing procedure. bztckground level in the test room and to ensure US 4024499. MAY 17, 1977. Application No. 482,002; that the test tone is repeated when the background Filed JUN 24, 1974. level exceeds a maximum value during the time that the test tone is produced. Adaptive Noise Suppressor: Ghabries-Douglas-M. US 41 57456. JUN 05, 1979. Application No. 877,826; Christiansen-Richard-W. Lynn-Douglas. Kenwor- Filed FEB 15, 1978. thy-Gary . An adaptive noise suppressor for providing noise Automatic Audiometer System: Charlebois-Jacques. filtered signals. The noise suppression device LescouAair-Guy . employs a vector gain *MU* for the weights of An audiometer for testing the hearing character- the filter wherein the vector *MU* is selected for istic of a person. The audiometer is entirely each frequency bin to be inversely proportional operable by the user whereby technicians are not to the power spectrum. A projection operator is required. The audiometer comprises a source of utilized to remove the effects of circular convo- audible and selectable fixed frequency signals. An lution to produce a linear convolution result wherein automatic frequency selector switch selects a the weights are reaausted in a manner to minimize predetermined frequency signal from the source. the difference between the input signal and the A variable attenuator circuit is provided to auto- filter output signal, thereby minimizing the error matically attenuate, in sequence, the predeter- signal to produce a noise suppressed signal in the mined frequency through a plurality of attenuation filtered output. A frequency suppression device levels and according to a preselected mode of utilizes the same principles of the vector "MU* operation whereby to transmit a plurality of at- and projection operator, but the output is taken tenuated frequency signals. The attenuated fre- from the error output of the filter. quency signals are transmitted for audible recep- US 4658426. APR 14,1987. Application No. 785,999; tion by the person using the audiometer. Visual Filed OCT 10. 1985. display lamps indicate the test frequencies and attenuation, permitting the used to fill out a test Adaptive Detector: McGool-John-M, Widrow-Ber- chart on corresponding sounds a~tdibleto his ears. nard. Nearn-Robert-H. Zeidler-James-R. Cka- A control circuit is provided to enable the fre- bries-Douglas-M. Moore-Randall-H. quency selector means and the variable attenuator An adaptive detector comprises an adaptive linear in accordance with a preselected mode of opera- prediction filter (ALPF) and a detection processor. tion. The adaptive filter comprises an input filter, adapted US 4107465. AUG 15, 1978. Application No. 863,238; to receive an input signal x(k) and delay it by a Filed DEC 22, 1977. time "DELTA*. An L-point, or L-tap, adaptive filter has an input connected to the output of the Audiornetric System: Bosscher-Jack-F, input filter, a signal r(k) appearing at the output Audiornetric system for monitoring manually-con- of the filter. A means for summing has two inputs, ducted hearing tests and for automatically record- one for receiving the signal x(k) and the other for ing the results of such tests. The system includes receiving an inverted signal from the adaptive a modified audiometer for applying tones to a filter, the output of the summer being an error subject at selected frequencies and amplitudes, signal *epsilon*(k). A feedback amplifier, whose and a data interface for converting the control input is connected to the output of the summer, settings of the audiometer to digital data in a takes a portion 2*MU*, of the output signal format suitable for operating printing apparatus *epsilon*(k) and feeds it back to the adaptive to make a printed record of the audiometric test filter, thereby modifying the tap weights of the data in predetermined format. The digital data adaptive filter. The detection processor comprises may also be recorded for subsequent analysis or a circuit, whose input is connected to the output other use. The data interface provides various of the adaptive filter, to receive the signal r(k), Journal sf Rehabilitation Research and Development Val. 24 Ms. 4 Fall 1987

for performing a K-point discrete Fourier trans- at a surface electrode worn by the amputee is fed form (DFT) on the signal r(k). A spectral analy~er, to each filter of thc above array of filters, and the whose input is connected to the output of the outputs of these various filters are used for a DFT circuit, performs a spectral analysis on the decision by the systenl as to which limb f~lnction output signal. should be actuated. In another realization, iclen- US 4243935. JAN 06, 1981. Application No. 040,25 1; tificatlon of partial correlation coefficients of the Filed MAY 18, 1979. ME signal is performed. These coefficients are stored in menlory per each limb function, and Adaptive Line Enhancer: McGool-John-M. Widsow- during nornlal operation the partial correlation Bernard, Zeidler-,James-R. Hearra-Robert-H. Cha- parameters for the c~irrentME signal are com- bries-Douglas-LW* pared with those in nmernory to determine which An input signal XG) is fed directly to the positive limb function is to he actuated. port of a summing function and is silnultaneorrsly US 4209864). JUL 01, 1980. Application No. 877,379; fed through a parallel channel in which it is Filed FEB 13, 1978. delayed, and passed througll an adaptive linear Iransversal filter, the output being then subtracled ARMA Filter and Method for Desigxring the Same: fro111 the inslantaneous input slglla1 XG). The Graupe-Daniel, Beex-Aloysins-A. Cawsey-G-Dola- difference, XG)-Vu), between the\e two signals ald, is the error- signal 'epsilon" (j). epsilon" 6) is A near minimum order AIIMA type recn~.sive multiplied by a gain XMU' and fed back lo the filter with guaranteed stability and convergence adaptive filter to readjust the weights of the filter.. is provided together with ;r method for obtaining The weights of the filter are reacl.justed until the parameters of wch filler. The amplitude1 'ep"rlona'G) is rnininlized according to the recw - frequency responre of the filler approximates an sive algorithm: ('See patent fa- mathematical arbitrarily selected frequency spectrum of an-rpli- equation*) where the arrow above tr term inclicates tude, and the phase response approximates a that the term is a signal vector. Th~r,, whcn the substantially linear I-'uncticrn of frequency with an mean5 square error is minimized, W(c I)-W(c, and arbitrarily selectecl slope because the paranreter 5 the filter is stabilized. are iclentified, ofcline, using a miniirnization proc- US $238746. DEC 09, 1980. Applicatiorr No. 888,266; ess that minimizes an integral error norm. The Filed MAR 20, l978. first step involves performxng an inverse cli5crele Fourier transform of Ihe arbitrarily selected fre- Syslen~and Method for Multifunctional Coratrol of qtlerlcy spectrum of amplitude to obtain a trun- Upper Limb Prosthesis via EM&:Signal Bdentifica- cated sequence of coefficient., of 21 stable, pure tion: Graupe-9arnie1, moving-average filter model, i.e. the paramekers A systern for controllirxg the operation of an of a non-recur5ive filter model. The trrrncated electrically powered prostl-retic appliance which sequerrce of coefficients, which has N i- I terms, l~eplacesan amputee's missing Iimb. 'The n~ethod is then convcslvecl with a randorn sequence to employed consists of conducting electrorny- obtain an output sequence associated with the sgraphic (EMC) signals frona the strrn~pof the random sequence. A time-drsmzun, cor-tvergcnt missirrg limb and processing the signal\ so as lo parameter identifici~tioni\ then performed, in a reduce them to a near minimunr number of llnean manrler that mininrizes an Integral err-or fr~rrction time cerie5 r~~oclelparameters effectrve to differ- norm, to obtain the near. minimurm order. param- entiate beljiireen each ol' the several ftunctions eter\ "ALPHA"(i)itnd I BETAYj)of the n~otlel performed by the nllsslng Iin-b from each other having the deiired amplitude- and phase-fre- ftinction thereof. A filter- ;array carried by the quency r.esponses, the paramreter5 sati\fy-'yrngthe amputee subseq~aentlyenlploys the identified pa- relation\hip: ('See patent for rniithernatlcal eqrra- rameter.\ SLIC~that each individual fileen of thc tion") wl-rere: ' AI,PHA9(i)is the ith auto-regr.es- array is tuned according to 641 \ek of g;zrameter\ she ~,araraaeter,and BETA" 6)is the jlh moving- related to one of the Iianb f~anctiunsconsideled. average paranaeter, respectively, of arx ARMA- The rnyoelectric (EMC; or ME) signal a\ cpbtilined type recursive filter; n and rn denote the order of Bibliographic Section: Patents Relating to Digital Hearing Aids

the auto-regressive and the moving-average parts Method of and Means for Processing an Audio Fre- of the ARMA model, respectively; y(k)and u(k)are quency Signal do Conceal lnlelligibility: Graupe- associated elements of the kth element of the Daniel, Goknn-David-L. Gausey-6- Donald, output sequence and the random sequence, re- An input audio li-equency analog signal, for ex- spectively; k is an Integer; and v is a shift integer ample, speech, which is to be passed through a selected to provide the desired slope of the phase noisy transmission channel, is scrambled at the response given by 2"pi"(v = NI2). sending end by repetitively perl-'orming a modulo- US 4 188667. Feb 12, 1980. Application No. 852,917; V (Mod V) addition of an N-level, M-pulse code- Filed Nov 18, 1977. word with an N-level digitized transformation of the input signal under the condition that M and Method and Means for AdapLiveXy Filtering Near- V are integers. The resultant sum signal, after Stationary Noise from an Information-Bearing Sig- transmission through a noisy channel (which may nal: Granpe-Daniell. Gausey-6-Donald. be an acoustic medium, a conventional telephone An input signal containing informatio~~such as link, a conventional CB radio link, etc.), is re- speech or nlusic as well as near-stationary noise ceived at the receiving end and descrambled. is applied in parallel to a noise-analysis circuit Descrambling is achieved by carrying out a Mod and a noise-reduction circuit, each of which com- V subtraction process involving repetitively sub- prises a plurality of bandpass filters covering the tracting the sarne codeword from an N-level dig- range of frequencies associated with the inbr- itized transformation of the received signal, the mation. The absolute value, or a function thereof, subtraction being carried out in synchronism with of the output of each bandpass filter in the noise- the addition at the sending end. The resultax~t analysis circuit is produced and smoothed. 'The difference signal is a representation of the input presence of near-stationary noise in the input signal and is relatively insensitive to noise present signal is determined by examining the nature of in the transmission cl~atlr~el. the smoothed signal in each band assuming noise US 4126761. NOV 21, 1978. Application No. 767,904; has a fi-equency spectrum which does not vary Filed FED 1 1, 1977. with ti~neor varies only wilhin a narrow range over a precletermined period of time with respect Method of and Means 60s Scrambling and Descram- to the spectral parameters of the information blixag Speech at Audio Frequencies: Graupe-Daniel, signal. 1E noise is detected, the noise-analysis Gausey -6-Dollaid, circuit identifies spectral paranleters of the infor- Processing an input arrdio-frequency analog sig- n~ationandlor noise in each band using the smoothed nal, for example, spcech, which is to be passed signal therein. In the preferred embodiment of the through a communication channel, ir~cltldesper- invention, the bandpass filters of the noise-reduc- forming an N-level digilizing of the ia-rput signal, tion circuit have gain clements that are adjusted transforming the levels of the digitized signal to in accordance with the identified parameters to other levels using a pre-selected N-bit transfor- minimize, under some continuous minimization mation code, and converting the transfornlcd criterion, the effect of the noise in the input signal digitized signal into analog form that is scrambled thus enhancing intelligibility of the information with respect 10 the input signal for transmission therein. Minilnization can be such That the gain- through the cornrnunication channel. At the re- to-parameter relationships are similal. to those in ceiving end of the channel, an N-level dlgiitizirrg Weincr or Kalman filtering theory with a-priori of the transmnitted signal is performed, followed knowledge of the noise, or of the lloise and by an inverse transformation of the Levels of the information, except that in this case, a-priori digitized signal sing the ir-rverse of the pre- knowledge of the noise is acquired via identifi- selected transformation code used on the digitized callon and is not preassurned. input signal. The inversely transhrmed signal is US 4185168. JAN 22, 1980. Application No. 866,938; then converted into an analog signal which is Filed JAN 04, 1978. representative of the input signal. The cornmu- nication channel can be an acoustic medium, a telephone line, or a CB radio link. The signal 304 Journal of Rehabilitation Research and Development Vol. 24 No. 4 Fall 1987

processing means can be realized using micropro- of the correction required by the person being cessors with fixed or variable programming to tested. The audiometer is provided with a pro- change the pre-selected transformation code, or gramming output adapted for coupling to a hearing tape or card readers to which a tape or card is aid for programming a hearing aid by applying the applied for the purpose of establishing the pre- program developed by the central processing unit selected transformation code. to the hearing aid. US 4086435. APR 25,1978. Application No. 724,170; US 4489610. Dec 25, 1984. Application No. 599,152; Filed SEP 17, 1976. Filed Apr 11, 1984.

Two-Channel Audio Communication System: LiRer- Method of and Means for Adaptively Filtering Near man-Zvie. Stationary Noise from Speech: Graupe-Daniel. A two channel intercommunication system has a Causey-Donald. high degree of noise immunity. The gain of each By identifying and analyzing the properties of the channel is controlled by a gain control loop proc- parameters of an input signal that contains speech essing circuit. The signal condition in one channel in the presence of simultaneously occuring near- turns off the other channel. Multiple active rec- stationary noise, pauses between speech intervals tifier-filter circ~itsdiscriminate between speech as well as as the termination of such noise can be and noise and provide tinling of control signals. recognized. When a pause interval containing US 4588859. May 13, 1986. Application No. 5 19,546; noise is recognized, the parameters identified Filed Aug 02, 1983. during such interval are used to set the parameters of an adaptive filter through which the input signal Computerized Audiometer: Slavin-Martin-J, is passed during subsequent intervals of speech A computerized audiometer is provided with at and until the noise terminates. During the time least one head set, a control switch, a tone the input signal passes through the filter, the near- generator for providing a plurality of sequential stationary noise is filtered out. In response to tones of different frequencies and amplifications recognition of the termination of noise, the input to at least one head set, and a central processing signal is caused to by-pass the filter which is then iuiit for receiving data representative of the reas- prepared to accept the parameters of noise oc- ponse to the test of the person being tested as curing in a subsequent pause, reflected by the operation of the control switch. US 4025721. May 24,1977. Application No. 683,234; The central processing unit is adapted to analyze Filed May 4, 1976. the test data and produce a program representative