The Effect of Peripheral Compression on Syllable Perception Measured with a Hearing Impairment Simulator

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1 The Effec of Peripheral Compression on Syllable Percepion Measured wih a Hearing Impairmen Simulaor Toshie Masui, Toshio Irino, Misaki Nagae, Hideki Kawahara and Roy D. Paerson Absrac Hearing impaired (HI) people ofen have difficuly undersanding speech in muli-speaker or noisy environmens. Wih HI liseners, however, i is ofen difficul o specify which sage, or sages, of audiory processing are responsible for he defici. There migh also be cogniive problems associaed wih age. In his paper, a HI simulaor, based on he dynamic, compressive gammachirp (dcgc) filerbank, was used o measure he effec of a loss of compression on syllable recogniion. The HI simulaor can counerac he cochlear compression in normal hearing (NH) liseners and, hereby, isolae he defici associaed wih a loss of compression in speech percepion. Liseners were required o idenify he second syllable in a hree-syllable nonsense word, and beween rials, he relaive level of he second syllable was varied, or he level of he enire sequence was varied. The difference beween he Speech Recepion Threshold (SRT) in hese wo condiions reveals he effec of compression on speech percepion. The HI simulaor adjused a NH lisener s compression o ha of he average 80-year old wih eiher normal compression or complee loss of compression. A reference condiion was included where he HI simulaor applied a simple 30-dB reducion in simulus level. The T. Masui ( ) T. Irino M. Nagae H. Kawahara Faculy of Sysems Engineering, Wakayama Universiy, Sakaedani 930, Wakayama-ciy , Japan masui@sys.wakayama-u.ac.jp T. Irino irino@sys.wakayama-u.ac.jp M. Nagae s155029@cener.wakayama-u.ac.jp H. Kawahara kawahara@sys.wakayama-u.ac.jp R. D. Paerson Deparmen of Physiology, Developmen and Neuroscience, Cenre for he Neural Basis of Hearing, Universiy of Cambridge, Downing Sree, Cambridge CB2 3EG, UK rdp1@cam.ac.uk The Auhor(s) 2016 P. van Dijk e al. (eds.), Physiology, Psychoacousics and Cogniion in Normal and Impaired Hearing, Advances in Experimenal Medicine and Biology 894, DOI / _32 307

2 308 T. Masui e al. resuls show ha he loss of compression has is larges effec on recogniion when he second syllable is aenuaed relaive o he firs and hird syllables. This is probably because he inernal level of he second syllable is aenuaed proporionaely more when here is a loss of compression. Keywords Hearing impairmen simulaor Cochlear compression Dynamic compressive gammachirp filerbank Audiogram 1 Inroducion Age relaed hearing loss (presbycusis) makes i difficul o undersand speech in noisy environmens and muli-speaker environmens (Moore 1995; Humes and Dubno 2010). There are several facors involved in presbycusis: loss of frequency seleciviy, recruimen, and loss of emporal fine srucure (Moore 2007). The isolaion and measuremen of hese differen aspecs of hearing impairmen (HI) in elderly liseners is no sraighforward, parly because hey ofen have muliple audiory problems, and parly because hey may also have more cenral cogniive problems including depression. Togeher he problems make i difficul o obain sufficien behavioral daa o isolae differen aspecs of HI (Jerger e al. 1989; Lopez e al. 2003). We have developed a compuaional model of HI and an HI simulaor ha allow us o perform behavioural experimens on cochlear compression experimens in which young normal hearing (NH) liseners ac as paiens wih isolaed, sensory-neural hearing losses of varying degree. The HI simulaor is essenially a high-fideliy synhesizer based on he dynamic, compressive gammachirp filer bank (dcgc-fb) (Irino and Paerson 2006). I analyses naurally recorded speech sounds wih a model of he audiory periphery ha includes fas-acing compression and hen resynhesizes he sounds in a form ha couneracs he compression in a NH lisener. They hear speech wih lile disorion or background noise (Irino e al. 2013) bu wihou heir normal compression. This makes i possible o invesigae recruimen phenomenon ha are closely relaed o loss of cochlear compression (Bacon e al. 2004) using NH liseners who have no oher audiory problems. Specifically, we describe an experimen designed o examine how he loss of cochlear compression affecs he recogniion of relaively sof syllables occurring in he presence of louder, flanking syllables of varying levels. The aim is o reveal he role of cochlear compression in muli-speaker environmens or hose wih disrupive background noise. 2 Mehod Liseners were presened hree-syllable nonsense words and required o idenify he second syllable. Beween rails, he level of he second syllable wihin he word was varied ( dip condiion) or he level of he enire word was varied ( consan

3 The Effec of Peripheral Compression on Syllable Percepion Measured 309 condiion). The difference beween second-syllable recogniion in he wo condiions reveals he effec of compression. The HI simulaor is used o adjus syllable level o simulae he hearing of 80 year old liseners wih normal presbycusis (80 year 100 %) or a complee loss of compression (80 year 0 %). 2.1 Paricipans Ten liseners paricipaed in he experimen (four males; average age: 23.6 years; SD: 4.8 years). None of he liseners repored any hisory of hearing impairmen. The experimen was approved by he ehics commiee of Wakayama Universiy and all liseners provided informed consen. Paricipans were paid for heir paricipaion, excep for he firs and hird auhors who also paricipaed in he experimen. 2.2 Simuli and Procedure The simuli were generaed in wo sages: Firs, hree-syllable nonsense words were composed from he recordings of a male speaker, idenified as MIS (FW03) in a speech sound daabase (Amano e al. 2006), and adjused in level o produce he dip and consan condiions of he experimen. Second, he HI simulaor was used o modify he simuli o simulae he hearing of wo 80 year old liseners, one wih average hearing for an 80 year old and one wih a complee loss of compression. There was also a normal-hearing conrol condiion in which he level was reduced a fixed 30 db. In he firs sage, nonsense words were composed by choosing he second syllable a random from he 50 Japanese syllables presened wihou parenheses in Table 1. This is he lis of syllables (57-S) recommended by he Japanese Audiological Sociey (2003) for use in clinical sudies o faciliae comparison of behavioural daa across sudies. The firs and hird syllables in he words were hen seleced a random from he full se of 62 syllables in Table 1. The se was enlarged o reduce he chance of liseners recognizing he resricion on he se used for he arge Table 1 The 62 Japanese syllables used in he experimen using he inernaional phoneic alphabe. The syllables in parenheses are also Japanese syllables bu no included in lis 57-S. All 62 were used in he draw for he firs and hird syllables. The draw for he second syllable was resriced o he 50 syllables no enclosed in parenheses a ka sa a na ha ma ja ɾa wa ɡa (dza) da ba i kʲi ʃi ʃi ɲi çi mi ɾʲi (ɡʲi) ʤi (bʲi) ɯ kɯ sɯ sɯ (nɯ) ɸu mɯ jɯ ɾɯ (ɡɯ) dzɯ (bɯ) e ke se e ne he me (ɾe) (ɡe) (dze) de (be) o ko so o no ho mo jo ɾo ɡo (dzo) do (bo)

4 310 T. Masui e al. Fig. 1 Schemaic of he experimenal paradigm. The levels of he nonsense words were adjused o produce simuli for a he Dip condiion and b he Consan condiion. The 70-dB simuli were he same in he wo condiions a Dip condiion 70 db 60 db b Consan condiion 70 db 60 db 50 db 50 db 50 ms ms 40 db 40 db Targe syllable (V, CV) Flanking syllable (V, CV) syllable. Syllable duraion ranged from 211 o 382 ms. There was a 50-ms silence beween adjacen syllables wihin a word. The nonsense words were hen adjused o produce he wo level condiions illusraed in Fig. 1: In he dip condiion (lef column), he level of he second syllable was 70, 60, 50 or 40 db, while he firs and hird syllables were fixed a 70 db. In he consan condiion (righ column), all hree syllables were se o 70, 60, 50 or 40 db. In he second sage, he simuli were processed o simulae: 1. he average hearing level of an 80 year old person (audiogram ISO7029, ISO/ TC ) simulaed wih 100 % compression (80 year 100 %), 2. he average hearing level of an 80-year-old simulaed wih 0 % compression (80 year 0 %), 3. normal adul hearing wih a 30-dB reducion across he enire frequency range (NH 30 db). To realize he 80 year 100 % condiion, he oupu level of each channel was decreased unil he audiogram of he dcgc-fb (normal hearing) mached he average audiogram of an 80 year old. To realize he 80 year 0 % condiion, an audiogram was derived wih he dcgc-fb having no compression whasoever, and hen he oupu level of each channel was decreased unil he audiogram mached he audiogram of an average 80 year old. In he compression-cancellaion process, loss of hearing level was limied so ha he audiogram did no fall below he hearing level of an average 80 year old. The compression was applied using he signal processing sysem described in Nagae e al. (2014).

5 The Effec of Peripheral Compression on Syllable Percepion Measured 311 Each paricipan performed all condiions a oal of 1050 rials of nonsense words: 50 words 7 dip/consan condiions 3 hearing impairmen simulaions. The paricipans were required o idenify he second syllable using a GUI on a compuer screen. The simuli were manipulaed, and he resuls colleced using MATLAB. The sounds were presened dioically via a DA converer (Fosex, HP- A8) over headphones (Sennheiser, HD-580). The experimen was carried ou in a sound-aenuaed room wih a background level of abou 26 db L AEq. 3 Resuls For each paricipan, he four percen-correc values for each level condiion (dip or consan) were fied wih a cumulaive Gaussian psychomeric funcion o provide a Speech Recepion Threshold (SRT) value for ha condiion, separaely in each of he hree simulaed hearing-impairmen condiions. The cumulaive Gaussian was fied by he boosrap mehod (Wichmann and Hill 2011a; Wichmann and Hill 2011b) and SRT was aken o be he sound pressure level associaed wih 50 % correc recogniion of he second syllable. The SRT in he consan condiion wih he NH 30 db hearing impairmen was aken as sandard performance on he ask. The difference beween his sandard SRT and he SRTs of he oher condiions are he experimenal resuls (ΔSRTs) for each paricipan. Figure 2a shows he mean and sandard deviaion over paricipans of ΔSRT for each condiion. a b ΔSRT re. NH -30 db & consan (db) NH -30 db 80 yr 100% 80 yr 0% ΔSRT re. consan (db) NH -30 db 80 yr 100% 80 yr 0% Consan Dip Fig. 2 a The difference in SRT (ΔSRT) beween he consan condiion of he NH 30 db simulaion and he SRTs of he oher condiions. b The SRT difference beween he dip and consan condiions for each hearing impairmen condiion. Aserisks ( *) show significan differences (α = 0.05) in a muliple comparison, Tukey-Kramer HSD es. Error bars show he sandard deviaion

6 312 T. Masui e al. A wo-way ANOVA was performed for he dip/consan condiions and he hearing impairmen condiions combined, and i showed ha he manipulaions had a significan effec on recogniion performance (ΔSRT) ( F(5, 54) = 23.82, p < ). Significan, separae main effecs were also observed for he dip/consan condiion and he hearing impairmen condiion ( F(1, 54) = 41.99, p < ; F(2, 54) = 36.11, p < , respecively). The ineracion beween he wo facors was no significan (α= 0.05). Muliple comparisons wih he Tukey-Kramer HSD es were performed. There were significan differences beween all of he hearing impairmen condiions (α= 0.05). ΔSRT provides a measure of he difficuly of he ask, and he saisical analysis shows ha he differen hearing impairmen simulaions vary in heir difficuly. In addiion, ΔSRT for he dip condiions is larger han ΔSRT for consan condiions for all of he hearing impairmen simulaions. This difference in difficuly could be he resul of forward masking since he gap beween offse of he firs syllable and he onse of he arge syllable is less han 100 ms, and he hird syllable limis any pos processing of he second syllable. The dip condiion would be expeced o produce more masking han he consan condiion, especially when he arge syllable is sandwiched beween syllables whose levels are 20 or 30 db greaer. The consan condiion only reveals differences beween he differen hearing impairmen simulaions. This does, however, include differences in audibiliy. Figure 2b shows he difference beween SRT in he dip and consan condiions; ha is, ΔSRT relaive o he consan condiion. I provides a measure of he amoun of any forward masking. A one-way ANOVA was performed o confirm he effec of hearing impairmen simulaion ( F(2, 29) = 6.14, p = ). A muliple comparisons es (Tukey-Kramer HSD) showed ha ΔSRT in he 80 year 0 % condiion was significanly greaer han in he 80 year 100 % condiion, or he NH 30 db condiion (α= 0.05). 4 Discussion I is assumed ha forward masking occurs during audiory neural processing, and ha i operaes on peripheral audiory oupu (i.e. neural firing in he audiory nerve). Since he compression componen of he peripheral processing is normal in boh he 80 year 100 % condiion and he NH 30 db condiion, he level difference beween syllable 2 and syllables 1 and 3 should be comparable in he peripheral oupu of any specific condiion. In his case, ΔSRT provides a measure of he more cenral masking ha occurs during neural processing. When he compression is cancelled, he level difference in he peripheral oupu for syllable 2 is greaer in he dip condiions. If he cenral masking is consan, independen of he audiory represenaion, he reducion of he oupu level for syllable 2 should be refleced in he amoun of masking, i.e. ΔSRT. This is like he descripion of he growh of masking by Moore (2012), where he growh of masking in a compressive sysem is observed o be slower han in a non-compressive sysem. Moore was describing experimens

7 The Effec of Peripheral Compression on Syllable Percepion Measured 313 where boh he signal and he masker were isolaed sinusoids. The resuls of he curren sudy show ha he effec generalizes o speech percepion where boh he arge and he inerference are broadband, ime-vary sounds. There are, of course, oher facors ha migh have affeced recogniion performance: The fac ha he same speaker provided all of he experimenal simuli migh have reduced he disinciveness of he arge syllable somewha, especially since syllable 2 was presened a a lower simulus level in he dip condiions. The fac ha liseners had o ype in heir responses migh also have decreased recogniion performance a lile compared o everyday lisening. I is also he case ha our randomly generaed nonsense words migh accidenally produce a syllable sequence ha is similar o a real word wih he resul ha he paricipan answers wih reference o heir menal dicionary and makes an error. Bu, all of hese poenial difficulies apply equally o all of he HI condiions, so i is unlikely ha hey would affec he resuls. This suggess ha he resuls ruly reflec he role of he loss of compression when lisening o speech in everyday environmens for people wih presbycusis or oher forms of hearing impairmen. I shows ha his new, model-based approach o he simulaion of hearing impairmen can be used o isolae he compression componen of audiory signal processing. I may also assis wih isolaion and analysis of oher aspecs of hearing impairmen. 5 Summary This paper repors an experimen performed o reveal he effecs of a loss of compression on he recogniion of syllables presened wih flucuaing level. The procedure involves using a filerbank wih dynamic compression o simulae hearing impairmen in normal hearing liseners. The resuls indicae ha, when he compression of normal hearing has been cancelled, i is difficul o hear syllables a low sound levels when hey are sandwiched beween syllables wih higher levels. The hearing losses observed in paiens will commonly involve muliple audiory problems and hey will inerac in complicaed ways ha make i difficul o disinguished he effecs of any one componen of audiory processing. The HI simulaor shows how a single facor can be isolaed using an audiory model, provided he model is sufficienly deailed. Acknowledgmens This work was suppored in par by JSPS Grans-in-Aid for Scienific Research (Nos , , and ).

8 314 T. Masui e al. Open Access This chaper is disribued under he erms of he Creaive Commons Aribuion- Noncommercial 2.5 License (hp://creaivecommons.org/licenses/by-nc/2.5/) which permis any noncommercial use, disribuion, and reproducion in any medium, provided he original auhor(s) and source are credied. The images or oher hird pary maerial in his chaper are included in he work s Creaive Commons license, unless indicaed oherwise in he credi line; if such maerial is no included in he work s Creaive Commons license and he respecive acion is no permied by sauory regulaion, users will need o obain permission from he license holder o duplicae, adap or reproduce he maerial. References Amano S, Sakamoo S, Kondo T, Suzuki Y (2006) NTT-Tohoku Universiy familiariy conrolled word liss (FW03). Speech resources consorium. Naional Insiue of Informaics, Japan Bacon SP, Fay R, Popper AN (eds) (2004) Compression: from cochlea o cochlear implans. Springer, New York Humes LE, Dubno JR (2010) Facors affecing speech undersanding in older aduls. In: Gordon-Salan S, Frisina RD, Popper AN, Fay RR (eds) The aging audiory sysem. Springer, New York, pp Irino T, Paerson RD (2006) A dynamic compressive gammachirp audiory filerbank. IEEE Trans Audio Speech Lang Process 14(6): Irino T, Fukawaase T, Sakaguchi M, Nisimura R, Kawahara H, Paerson RD (2013) Accurae esimaion of compression in simulaneous masking enables he simulaion of hearing impairmen for normal hearing liseners. In: Moore BCJ, Paerson RD, Winer IM, Carlyon RP, Gockel HE (eds) Basic aspecs of hearing, physiology and percepion. Springer, New York, pp ISO/TC43 (2000) Acousics saisical disribuion of hearing hresholds as a funcion of age. Inernaional Organizaion for Sandardizaion, Geneva Japan Audiological Sociey (2003) The 57-S syllable lis. Audiol Jpn 46: Jerger J, Jerger S, Oliver T, Pirozzolo F (1989) Speech undersanding in he elderly. Ear Hear 10(2):79 89 Lopez OL, Jagus WJ, DeKosky ST, Becker JT, Fizparick A, Dulberg C, Breiner J, Lykesos C, Jones B, Kawas C, Carlson M, Kuller LH (2003) Prevalence and classificaion of mild cogniive impairmen in he cardiovascular healh sudy cogniion sudy: par 1. Arch Neurol 60(10): Moore BCJ (1995) Percepual consequences of cochlear damage. Oxford Universiy Press, New York Moore BCJ (2007) Cochlear hearing loss: physiological, psychological and echnical issues. Wiley, Chicheser Moore BCJ (2012) An inroducion o he psychology of hearing, 6h edn. Emerald Group Publishing Limied, Bingley Nagae M, Irino T, Nishimura R, Kawahara H, Paerson RD (2014). Hearing impairmen simulaor based on compressive gammachirp filer. Proceedings of APSIPA ASC Wichmann FA, Hill NJ (2011a) The psychomeric funcion: I. Fiing, sampling, and goodness of fi. Percep Psychophys 63(8): Wichmann FA, Hill NJ (2011b) The psychomeric funcion: II. Boosrap-based confidence inervals and sampling. Percep Psychophys 63(8):