masking of speech by amplitude modulated noise the masking of speech by amplitude modulated and unmodulated speech spectrum noise has been evaluated by the measurement of monaural speech recognition in such noise on young and elderly subjects with normal hearing and elderly hearing impaired subjects with and without a hearing aid sinusoidal modulation with frequencies covering the range 2 100 hz as well as an irregular modulation generated by the sum of four sinusoids in random phase relation was used modulation degrees were 100 6 db and 12 db root mean square sound pressure level was equal for modulated and unmodulated maskers for the normal hearing subjects essentially all types of modulated noise provided some release of speech masking as compared to unmodulated noise sinusoidal modulation provided more release of masking than the irregular modulation the release of masking increased with modulation depth it is proposed that the number and duration of low level intervals are essential factors for the degree of masking the release of masking was found to reach a maximum at a modulation frequency between 10 and 20 hz for sinusoidal modulation for elderly hearing impaired subjects the release of masking obtained from amplitude modulation was consistently smaller than in the normal hearing groups presumably related to changes in auditory temporal resolution caused by the hearing loss the average speech to noise ratio required for 30 correct speech recognition varied greatly between the groups for young normal hearing subjects it was 15 db for elderly normal hearing it was 9 db for elderly hearing impaired subjects in the unaided listening condition it was 2 db and in the aided condition it was 3 db the results support the conclusion that within the methodological context of the study age as well as sensorineural hearing loss as such influence speech recognition in noise more than what can be explained by the loss of audibility according to the audiogram and the masking noise spectrum

speech perception in gated noise the effects of temporal resolution previous investigations have suggested that hearing impaired hi listeners have reduced masking release mr compared to normal hearing listeners nh when they listen in modulated noise the current study examined the following questions that have not been clearly answered first when hi listeners are amplified so that their performance is equal to that of nh listeners in quiet and in steady noise do hi listeners still show reduced mr with modulated noise when compared to nh listeners second is the masking release the same for sentences and cv syllables third does forward masking significantly contribute to the variability in performance among hi listeners to compensate for reduced hearing sensitivity for hi listeners the spectrum levels of both speech and noise were adjusted based on the individual hearing loss there was no significant difference between the performance of nh listeners and that of hi listeners in steady noise and in quiet however the amount of mr for sentences and for cv syllables was significantly reduced for hi listeners for sentence recognition the amount of mr seemed to be more related to hearing sensitivity for low to mid frequencies than to forward masking in contrast forward masking thresholds appear to be a major contributor to the amount of mr for syllable recognition

the effects of hearing loss on the contribution of high and low frequency speech information to speech understanding ii sloping hearing loss the speech understanding of persons with sloping high frequency hf hearing impairment hi was compared to normal hearing nh controls and previous research on persons with flat losses hornsby and ricketts 2003 j acoust soc am 113 1706 1717 to examine how hearing loss configuration affects the contribution of speech information in various frequency regions speech understanding was assessed at multiple low and high pass filter cutoff frequencies crossover frequencies defined as the cutoff frequencies at which low and high pass filtering yielded equivalent performance were significantly lower for the sloping hi compared to nh group suggesting that hf hi limits the utility of hf speech information speech intelligibility index calculations suggest this limited utility was not due simply to reduced audibility but also to the negative effects of high presentation levels and a poorer than normal use of speech information in the frequency region with the greatest hearing loss the hf regio

local well posedness and quantitative ill posedness for the ostrovsky equation in this article we consider the initial value problem ivp for the ostrovsky equation tu x3u x 1u u xu 0 x r t r u x 0 u0 x with initial data in sobolev spaces hs r we prove that if s 34 this ivp is locally well posed in hs r and if s 34 the ivp is not quantitatively well posed in hs r

recovery from on and off frequency forward masking in listeners with normal and impaired hearing the aim of this study was to investigate the possible mechanisms underlying an effect reported earlier wojtczak m and oxenham a j 2009 j acoust soc am 125 270 281 in normal hearing listeners whereby recovery from forward masking can be slower for off frequency tonal maskers than for on frequency tonal maskers that produce the same amount of masking at a 0 ms masker signal delay to rule out potential effects of confusion between the tonal signal and tonal masker one condition used a noise band forward masker to test whether the effect involved temporal build up another condition used a short duration 30 ms forward masker to test whether the effect is dependent on normal cochlear function conditions were tested in five listeners with sensorineural hearing loss for the 150 ms noise maskers the data from normal hearing listeners replicated the findings from the previous study that used tonal maskers in contrast no significant difference in recovery from on and off frequency masking was observed for the 30 ms tonal maskers in normal hearing listeners or for the 150 ms tonal maskers in hearing impaired listeners overall the results are consistent with a mechanism based on efferent feedback that affects the recovery from forward masking in the normal auditory system

pulse number discrimination by cope s gray treefrog hyla chrysoscelis in modulated and unmodulated noise in cope s gray treefrog hyla chrysoscelis thresholds for recognizing conspecific calls are lower in temporally modulated noise backgrounds compared with unmodulated noise the effect of modulated noise on discrimination among different conspecific calls is unknown in quiet females prefer calls with relatively more pulses this study tested the hypotheses that noise impairs selectivity for longer calls and that processes akin to dip listening in modulated noise can ameliorate this impairment in two stimulus choice tests female subjects were allowed to choose between an average length call and a shorter or longer alternative tests were replicated at two signal levels in quiet and in the presence of chorus shaped noise that was unmodulated modulated by a sinusoid or modulated by envelopes resembling natural choruses when subjects showed a preference it was always for the relatively longer call noise reduced preferences for longer calls but the magnitude of this reduction was unrelated to whether the noise envelope was modulated or unmodulated together the results are inconsistent with the hypothesis that dip listening improves a female gray treefrog s ability to select longer calls in modulated compared with unmodulated noise

white noise driven ostrovsky equation abstract the current paper is devoted to the cauchy problem for the white noise driven ostrovsky equation with positive dispersion we obtain the local well posedness for the initial data u 0 h s r a e which is f 0 measurable with s 3 4 and l 2 0 s l 2 0 l 2 r h s 1 2 r and the globally well posedness for the initial data u 0 l 2 r a e which is f 0 measurable and l 2 0 0 l 2 0 l 2 r h 0 1 2 r the key ingredients that we used in this paper are some bilinear estimates in x s b type spaces given in subsection 2 1 ito formula the bdg inequality and stopping time techniques as well as frequency truncated technique our method can be applied to the case 0 which is just the kdv equation thus our result improves the local well posedness result of a de bouard a debussche and y tsutsumi 1999 3

temporal integration and compression near absolute threshold in normal and impaired ears the decrease in absolute threshold with increasing stimulus duration often referred to as temporal integration is greater for listeners with normal hearing than for listeners with sensorineural hearing loss it has been suggested that the difference is related to reduced basilar membrane bm compression in the impaired group the present experiment tested this hypothesis by comparing temporal integration and bm compression in normal and impaired ears at low levels absolute thresholds were measured for 4 24 and 44 ms pure tone signals with frequencies f s of 2 and 4 khz the difference between the absolute thresholds for the 4 and 24 ms signals was used as a measure of temporal integration compression near threshold was estimated by measuring the level of a 100 ms off frequency 0 45f s pure tone forward masker required to mask a 44 ms pure tone signal presented at sensation levels of 5 and 10 db there was a significant negative correlation between amount of temporal integration and absolute threshold however there was no correlation between absolute threshold and compression at low levels both normal and impaired ears showed a nearly linear response the results suggest that the differences in integration between normal and impaired ears cannot be explained by differences in bm compression

simulation of the effects of loudness recruitment and threshold elevation on the intelligibility of speech in quiet and in a background of speech these experiments simulated the threshold elevation and loudness recruitment associated with three different types of cochlear hearing loss moderate flat condition r2 severe flat condition r3 and moderate to severe sloping condition rx this was done to allow an examination of the effects of these factors on the intelligibility of speech in isolation from other factors that are normally associated with cochlear hearing loss such as reduced frequency selectivity the simulation was performed by splitting the input signal into 13 frequency bands and processing the envelope in each band so as to create loudness sensations in a normal ear that would resemble those produced in an impaired ear with recruitment the bands were then recombined all tests were performed using subjects with normal hearing for speech in quiet simulation of hearing loss produced a reduction in the ability to understand low level speech however speech at sufficiently high levels was highly intelligible in all conditions linear amplification according to the national acoustic laboratory nal prescription gave high intelligibility for speech at normal conversational levels for speech presented at a fixed input level of 65 db spl against a background of a single competing talker simulation of hearing loss produced substantial decrements in performance the speech to background ratios in conditions r2 and rx had to be 11 13 db higher than in the control condition unprocessed stimuli to achieve similar levels of performance linear amplification according to the nal prescription improved performance markedly for the conditions simulating flat losses but was less effective for the condition simulating a sloping loss this indicates that threshold elevation combined with recruitment produces a loss of intelligibility for speech in the presence of a single competing talker that is only partly compensated by linear amplification of the type typically used in hearing aids

on uniqueness properties of solutions of the k generalized kdv equations in this paper we study uniqueness properties of solutions of the so called k generalized korteweg de vries equations our goal is to obtain sufficient conditions on the behavior of the difference u1 u2 of two solutions u1 u2 of 1 1 at two different times t0 0 and t1 1 which guarantee that u1 u2

correspondence between behavioral and individually optimized otoacoustic emission estimates of human cochlear input output curves previous studies have shown a high within subject correspondence between distortion product otoacoustic emission dpoae input output i o curves and behaviorally inferred basilar membrane bm i o curves for frequencies above 2 khz for lower frequencies dpoae i o curves contained notches and plateaus that did not have a counterpart in corresponding behavioral curves it was hypothesized that this might improve by using individualized optimal dpoae primary levels here data from previous studies are re analyzed to test this hypothesis by comparing behaviorally inferred bm i o curves and dpoae i o curves measured with well established group average primary levels and two individualized primary level rules one optimized to maximize dpoae levels and one intended for primaries to evoke comparable bm responses at the f2 cochlear region test frequencies were 0 5 1 and 4 khz behavioral i o curves were obtained from temporal forward masking curves results showed high within subject correspondence between behavioral and dpoae i o curves at 4 khz only regardless of the primary level rule plateaus and notches were equally common in low frequency dpoae i o curves for individualized and group average dpoae primary levels at 0 5 and 1 khz results are discussed in terms of the adequacy of dpoae i o curves for inferring individual cochlear nonlinearity characteristics

relations between frequency selectivity temporal fine structure processing and speech reception in impaired hearing frequency selectivity temporal fine structure tfs processing and speech reception were assessed for six normal hearing nh listeners ten sensorineurally hearing impaired hi listeners with similar high frequency losses and two listeners with an obscure dysfunction od tfs processing was investigated at low frequencies in regions of normal hearing through measurements of binaural masked detection tone lateralization and monaural frequency modulation fm detection lateralization and fm detection thresholds were measured in quiet and in background noise speech reception thresholds were obtained for full spectrum and lowpass filtered sentences with different interferers both the hi listeners and the od listeners showed poorer performance than the nh listeners in terms of frequency selectivity tfs processing and speech reception while a correlation was observed between the monaural and binaural tfs processing deficits in the hi listeners no relation was found between tfs processing and frequency selectivity the effect of noise on tfs processing was not larger for the hi listeners than for the nh listeners finally tfs processing performance was correlated with speech reception in a two talker background and lateralized noise but not in amplitude modulated noise the results provide constraints for future models of impaired auditory signal processing

the problem of s m ulam for approximately multiplicative mappings in the present paper we study the problem of s m ulam for approximately multiplicative mappings and we consider new open problems

masking of speech by amplitude modulated noise abstract the degree of masking of human speech by environmental noise may be influenced by amplitude variations in the noise the listener s condition with respect to age and auditory function may affect his sensitivity to such noise also fatigue effects are possible after prolonged exposure to masking noise these aspects have been tested in the present study the results show that in general amplitude modulation of a masking noise reduces its speech masking effect as compared to unmodulated noise of the same r m s sound level and spectrum age did not affect the release of masking found in am noise however hearing impaired listeners obtained much less release of speech masking than those with normal hearing small but statistically significant fatigue effects were found after up to 60 min exposure to noise at 60 db spl the speech to noise ratio needed for 30 correct speech recognition was significantly affected by both age and hearing loss

effects of spectral smearing and temporal fine structure distortion on the fluctuating masker benefit for speech at a fixed signal to noise ratio normal hearing listeners receive less benefit from momentary dips in the level of a fluctuating masker for speech processed to degrade spectral detail or temporal fine structure tfs than for unprocessed speech this has been interpreted as evidence that the magnitude of the fluctuating masker benefit fmb reflects the ability to resolve spectral detail and tfs however the fmb for degraded speech is typically measured at a higher signal to noise ratio snr to yield performance similar to normal speech for the baseline stationary noise condition because the fmb decreases with increasing snr this snr difference might account for the reduction in fmb for degraded speech in this study the fmb for unprocessed and processed tfs removed or spectrally smeared speech was measured in a paradigm that adjusts word set size rather than snr to equate stationary noise performance across processing conditions compared at the same snr and percent correct level but with different set sizes processed and unprocessed stimuli yielded a similar fmb for four different fluctuating maskers speech modulated noise one opposite gender interfering talker two same gender interfering talkers and 16 hz interrupted noise these results suggest that for these maskers spectral or tfs distortions do not directly impair the ability to benefit from momentary dips in masker level

factors affecting masking release for speech in modulated noise for normal hearing and hearing impaired listeners the speech reception threshold for sentences in stationary noise and in several amplitude modulated noises was measured for 8 normal hearing listeners 29 sensorineural hearing impaired listeners and 16 normal hearing listeners with simulated hearing loss this approach makes it possible to determine whether the reduced benefit from masker modulations as often observed for hearing impaired listeners is due to a loss of signal audibility or due to suprathreshold deficits such as reduced spectral and temporal resolution which were measured in four separate psychophysical tasks results show that the reduced masking release can only partly be accounted for by reduced audibility and that when considering suprathreshold deficits the normal effects associated with a raised presentation level should be taken into account in this perspective reduced spectral resolution does not appear to qualify as an actual suprathreshold deficit while reduced temporal resolution does temporal resolution and age are shown to be the main factors governing masking release for speech in modulated noise accounting for more than half of the intersubject variance their influence appears to be related to the processing of mainly the higher stimulus frequencies results based on calculations of the speech intelligibility index in modulated noise confirm these conclusions

mathematical treatment of context effects in phoneme and word recognition percent recognition of phonemes and whole syllables measured in both consonant vowel consonant cvc words and cvc nonsense syllables is reported for normal young adults listening at four signal to noise s n ratios similar data are reported for the recognition of words and whole sentences in three types of sentence high predictability hp sentences with both semantic and syntactic constraints low predictability lp sentences with primarily syntactic constraints and zero predictability zp sentences with neither semantic nor syntactic constraints the probability of recognition of speech units in context pc is shown to be related to the probability of recognition without context pi by the equation pc 1 1 pi k where k is a constant the factor k is interpreted as the amount by which the channels of statistically independent information are effectively multiplied when contextual constraints are added empirical values of k are approximately 1 3 and 2 7 for word and sentence context respe

temporal masking functions for listeners with real and simulated hearing loss a functional simulation of hearing loss was evaluated in its ability to reproduce the temporal masking functions for eight listeners with mild to severe sensorineural hearing loss each audiometric loss was simulated in a group of age matched normal hearing listeners through a combination of spectrally shaped masking noise and multi band expansion temporal masking functions were obtained in both groups of listeners using a forward masking paradigm in which the level of a 110 ms masker required to just mask a 10 ms fixed level probe 5 10 db sl was measured as a function of the time delay between the masker offset and probe onset at each of four probe frequencies 500 1000 2000 and 4000 hz temporal masking functions were obtained using maskers that were 0 55 1 0 and 1 15 times the probe frequency the slopes and y intercepts of the masking functions were not significantly different for listeners with real and simulated hearing loss the y intercepts were positively correlated with level of hearing loss while the slopes were negatively correlated the ratio of the slopes obtained with the low frequency maskers relative to the on frequency maskers was similar for both groups of listeners and indicated a smaller compressive effect than that observed in normal hearing listeners

on the stability of functional equations in banach spaces the paper is devoted to some results on the problem of s m ulam for the stability of functional equations in banach spaces the problem was posed by ulam 60 years ago

generalized hyers ulam rassias stability of n sesquilinear quadratic mappings on banach modules over c algebras assume that x is a left banach module over a unital c algebra a it is shown that almost every n sesquilinear quadratic mapping h xxxxx n a is an n sesquilinear quadratic mapping when h rx y z 1 z n h x ry z 1 z n h x y rz 1 z 2 z n h x y z 1 z 2 rz n rh x y z 1 z 2 z n r 0 r 1 holds for all x y z 1 z email protected x moreover we prove the generalized hyers ulam rassias stability of an n sesquilinear quadratic mapping on a left banach module over a unital c algebra

additivity of masking in normally hearing and hearing impaired subjects the effects of combining two equally effective maskers were studied in normally hearing and elderly hearing impaired subjects the additivity of nonsimultaneous masking was investigated by measuring thresholds for a brief 4 khz signal in the presence of a broadband noise forward masker a backward masker and a combination of both for the normally hearing subjects combining two equally effective nonsimultaneous maskers resulted in up to a 15 db greater increase in threshold than the 3 db predicted by an energy summation model excess masking however the hearing impaired subjects showed little or no excess masking the difference between the two groups is consistent with a theory linking excess masking to the compressive transfer function measured on the basilar membrane bm in the hearing impaired subjects the transfer function is more linear accounting for the lack of excess masking the additivity of simultaneous masking was investigated by measuring thresholds for a 100 ms 4 khz signal in the presence of either a 400 ms broadband noise masker or a 400 ms sinusoidal masker at the same frequency as the signal and then combining two equally effective maskers a noise and a tone the maximum amount of excess masking 3 to 4 db was similar across the two groups of subjects consistent with an explanation based on the use of different detection cues for the tonal and noise maskers it is argued that while peripheral compression may underlie excess masking for pairs of nonsimultaneous maskers it is unlikely that in simultaneous masking where the maskers are close in frequency to the signal the two maskers are compressed individually before their effects are combined it is further suggested that bm nonlinearity may underlie the effects of the upward spread of masking and the nonlinear growth of forward masking as well as accounting for the additivity of simultaneous masking when the masker frequencies are well below that of the signal

consonant identification in noise using hilbert transform temporal fine structure speech and recovered envelope speech for listeners with normal and impaired hearing consonant identification ability was examined in normal hearing nh and hearing impaired hi listeners in the presence of steady state and 10 hz square wave interrupted speech shaped noise the hilbert transform was used to process speech stimuli 16 consonants in a c a syllables to present envelope cues temporal fine structure tfs cues or envelope cues recovered from tfs speech the performance of the hi listeners was inferior to that of the nh listeners both in terms of lower levels of performance in the baseline condition and in the need for higher signal to noise ratio to yield a given level of performance for nh listeners scores were higher in interrupted noise than in steady state noise for all speech types indicating substantial masking release for hi listeners masking release was typically observed for tfs and recovered envelope speech but not for unprocessed and envelope speech for both groups of listeners tfs and recovered envelope speech yielded similar levels of performance and consonant confusion patterns the masking release observed for tfs and recovered envelope speech may be related to level effects associated with the manner in which the tfs processing interacts with the interrupted noise signal rather than to the contributions of tfs cues per se

the effects of hearing loss on the contribution of high and low frequency speech information to speech understanding the speech understanding of persons with flat hearing loss hi was compared to a normal hearing nh control group to examine how hearing loss affects the contribution of speech information in various frequency regions speech understanding in noise was assessed at multiple low and high pass filter cutoff frequencies noise levels were chosen to ensure that the noise rather than quiet thresholds determined audibility the performance of hi subjects was compared to a nh group listening at the same signal to noise ratio and a comparable presentation level although absolute speech scores for the hi group were reduced performance improvements as the speech and noise bandwidth increased were comparable between groups these data suggest that the presence of hearing loss results in a uniform rather than frequency specific deficit in the contribution of speech information measures of auditory thresholds in noise and speech intelligibility index sii calculations were also performed these data suggest that differences in performance between the hi and nh groups are due primarily to audibility differences between groups measures of auditory thresholds in noise showed the effective masking spectrum of the noise was greater for the hi than the nh subjects

on the cauchy rassias stability of a generalized additive functional equation let x and y be banach spaces and f x y an odd mapping we solve the following generalized additive functional equation rf j 1dxjr j 0 1 j 1d j lrf j 1d 1 j xjr cld 1 cl 1d 1 1 j 1df xj for all x1 xd x moreover we deal with the above functional equation in banach modules over a c algebra and obtain generalizations of the cauchy rassias stability the concept of cauchy rassias stability for the linear mapping was originated from th m rassias s stability theorem that appeared in his paper th m rassias on the stability of the linear mapping in banach spaces proc amer math soc 72 1978 297 300

unique continuation for some evolution equations this work is concerned with unique continuation results for some evolution equations essentially of parabolic type to be more precise let l be an evolution operator acting on functions defined on some connected open set b of r r x r l is said to have the unique continuation property if every solution u of lu 0 which vanishes one some nonempty open set u i of fl vanishes in the horizontal component of o in 0 i e in x t e 0 3x x t e co the first general result of this type was established by mizohata 6 in the case where l is a second order parabolic operator with smooth coefficients however mizohata s proof is somewhat delicate it is based in particular on an extended class of calderon zygmund operators and does not lead obviously to a weakening of the smoothness of the coefficients on the other hand it is important for the applications to deal with nonsmooth coefficients since l is often obtained as the linearization of some nonlinear operator at a nonnecessarily smooth solution we refer to lions 4 and kernevez and lions 3 for applications to control theory and to 1 l for applications to transversality techniques let us now describe the content of this work in the first section we prove a unique continuation theorem when l is a second order parabolic equation our proof is simple and based on the derivation of a carleman estimate which is reminiscent of the classical carleman estimates for second order elliptic operators see 121 this carleman inequality allows the weakening of the 118 0022 0396187 3 00

generalized additive mapping in banach modules and isomorphisms between c algebras abstract let x y be vector spaces it is shown that if an odd mapping f x y satisfies the functional equation 1 r f j 1 d x j r j 0 1 j 1 d j l r f j 1 d 1 j x j r c l d 1 c l 1 d 1 1 j 1 d f x j then the odd mapping f x y is additive and we prove the hyers ulam stability of the functional equation 1 in banach modules over a unital c algebra as an application we show that every almost linear bijection h a b of a unital c algebra a onto a unital c algebra b is a c algebra isomorphism when h 2 n r n u y h 2 n r n u h y for all unitaries u a all y a and n 0 1 2

on the hyers ulam stability of linear mappings abstract let e1 be a real normed vector space and e2 a real banach space s m ulam posed the problem when does a linear mapping near an approximately linear mapping e1 e2 exist we give a new generalized solution to this problem an example illustrates when the answer to this question is negative the behaviour of bounded approximately additive mappings which do not satisfy hyers uiam stability is also investigated

on the stability of the linear mapping in banach modules abstract we prove the generalized hyers ulam rassias stability of the linear mapping in banach modules over a unital banach algebra

a behavioral measure of basilar membrane nonlinearity in listeners with normal and impaired hearing this paper examines the possibility of estimating basilar membrane bm nonlinearity using a psychophysical technique the level of a forward masker required to mask a brief signal was measured for conditions where the masker was either at or one octave below the signal frequency the level of the forward masker at masked threshold provided an indirect measure of the bm response to the signal as follows consistent with physiological studies it was assumed that the bm responds linearly to frequencies well below the characteristic frequency cf thus the ratio of the slopes of the masking functions between a masker at the signal frequency and a masker well below the signal frequency should provide an estimate of bm compression at cf results obtained from normally hearing listeners were in quantitative agreement with physiological estimates of bm compression furthermore differences between normally hearing listeners and listeners with cochlear hearing impairment were consistent with the physiological effects of damage to the cochlea the results support the hypothesis that bm nonlinearity governs the nonlinear growth of the upward spread of masking and suggest that this technique provides a straightforward method for estimating bm nonlinearity in humans

the cauchy problem for the ostrovsky equation with negative dispersion at the critical regularity abstract in this paper we investigate the cauchy problem for the ostrovsky equation x u t x 3 u 1 2 x u 2 u 0 in the sobolev space h 3 4 r here 0 0 corresponds to the positive negative dispersion of the media respectively p isaza and j mejia 2006 13 2009 15 k tsugawa 2009 26 proved that the problem is locally well posed in h s r when s 3 4 and ill posed when s 3 4 by using some modified bourgain spaces we prove that the problem is locally well posed in h 3 4 r with 0 and 0 the new ingredient that we introduce in this paper is lemma 2 1 lemma 2 2 lemma 2 3 lemma 2 4 lemma 2 5 lemma 2 6

estimating peripheral gain and compression using fixed duration masking curves estimates of human basilar membrane gain and compression obtained using temporal masking curve tmc and additivity of forward masking afm methods with long duration maskers or long masker signal silent intervals may be affected by olivocochlear efferent activation which reduces basilar membrane gain the present study introduces a fixed duration masking curve fdmc method which involves a comparison of off and on frequency forward masker levels at threshold as a function of masker and signal duration with the total masker signal duration fixed at 25 ms to minimize efferent effects gain and compression estimates from the fdmc technique were compared with those from tmc 104 ms maskers and afm 10 and 200 ms maskers methods compression estimates over an input masker range of 40 60 db sound pressure level were similar for the four methods maximum compression occurred at a lower input level for the fdmc compared to the tmc method estimates of gain were similar for tmc and fdmc methods the fdmc

a generalization of the hyers ulam rassias stability of approximately additive mappings abstract in this paper we prove a generalization of the stability of approximately additive mappings in the spirit of hyers ulam and rassias

use of psychometric function slopes for forward masked tones to investigate cochlear nonlinearity schairer et al 2003 effects of peripheral nonlinearity on psychometric functions for forward masked tones j acoust soc am 133 1560 1573 demonstrated that cochlear nonlinearity is reflected in psychometric function pf slopes for 4 khz forward masked tones the goals of the current study were to use pf slopes to compare the degree of compression between signal frequencies of 0 25 and 4 khz in listeners with normal hearing lnh and between lnh and listeners with cochlear hearing loss lhl forward masked thresholds were estimated in lnh and lhl using on and off frequency maskers and 0 25 and 4 khz signals in three experiments pfs were reconstructed from adaptive procedure data for each subject in each condition trends in pf slopes across conditions suggest comparable compression at 0 25 and 4 khz and potentially a wider bandwidth of compression in relative frequency at 0 25 khz this is consistent with other recent behavioral studies that revise earlier estimates of less compression at lower frequencies the preliminary results in lhl demonstrate that pf slopes are abnormally steep at frequencies with hl but are similar to those for lnh at frequencies with nh overall the results are consistent with the notion that pf slopes reflect degree of cochlear nonlinearity and can be used as an additional measure of compression across frequency

speech reception by listeners with real and simulated hearing impairment effects of continuous and interrupted noise the effects of audibility and age on masking for sentences in continuous and interrupted noise were examined in listeners with real and simulated hearing loss the absolute thresholds of each of ten listeners with sensorineural hearing loss were simulated in normal hearing listeners through a combination of spectrally shaped threshold noise and multi band expansion for octave bands with center frequencies from 0 25 8 khz each individual hearing loss was simulated in two groups of three normal hearing listeners an age matched and a non age matched group the speech to noise ratio s n for 50 correct identification of hearing in noise test hint sentences was measured in backgrounds of continuous and temporally modulated 10 hz square wave noise at two overall levels for unprocessed speech and for speech that was amplified with the nal rp prescription the s n in both continuous and interrupted noise of the hearing impaired listeners was relatively well simulated in both groups of normal hearing listeners thus release from masking the difference in s n obtained in continuous versus interrupted noise appears to be determined primarily by audibility minimal age effects were observed in this small sample observed values of masking release were compared to predictions derived from intelligibility curves generated using the extended speech intelligibility index esii rhebergen et al 2006 j acoust soc am 120 3988 3997

measuring the threshold for speech reception by adaptive variation of the signal bandwidth ii hearing impaired listeners in a previous study noordhoek et al j acoust soc am 105 2895 2902 1999 an adaptive test was developed to determine the speech reception bandwidth threshold srbt i e the width of a speech band around 1 khz required for a 50 intelligibility score in this test the band filtered speech is presented in complementary bandstop filtered noise in the present study the performance of 34 hearing impaired listeners was measured on this srbt test and on more common srt speech reception threshold tests namely the srt in quiet the standard srt in noise standard speech spectrum and the spectrally adapted srt in noise fitted to the individual s dynamic range the aim was to investigate to what extent the performance on these tests could be explained simply from audibility as estimated with the sii speech intelligibility index model or require the assumption of suprathreshold deficits for most listeners an elevated srt in quiet or an elevated standard srt in noise could be explained on the basis of audibility for the spectrally adapted srt in noise and especially for the srbt the data of most listeners could not be explained from audibility suggesting that the effects of suprathreshold deficits may be present possibly such a deficit is an increased downward spread of masking

growth of masking as a measure of response growth in hearing impaired listeners growth of masking functions were obtained from 19 normal and 5 hearing impaired listeners using a simultaneous masking paradigm when masker and probe frequency are identical the slope of masking approximates 1 0 for both normal hearing and impaired listeners for masker frequencies less than or greater than probe frequency the slopes for impaired listeners are shallower than those of normals these findings are consistent with previously reported physiological data single fiber rate versus level and ap masking functions for animals with induced cochlear lesions results are discussed in terms of a potential masking technique to estimate the growth of response in normal and impaired ears

comparison of distortion product otoacoustic emission growth rates and slopes of forward masked psychometric functions slopes of forward masked psychometric functions fm pfs were compared with distortion product otoacoustic emission dpoae input output i o parameters at 1 and 6 khz to test the hypothesis that these measures provide similar estimates of cochlear compression implicit in this hypothesis is the assumption that both dpoae i o and fm pf slopes are functionally related to basilar membrane bm response growth fm pf slope decreased with signal level but this effect was reduced or reversed with increasing hearing loss there was a trend of decreasing psychometric function pf slope with increasing frequency consistent with greater compression at higher frequencies dpoae i o functions at 6 khz exhibited an increase in the breakpoint of a two segment slope as a function of hearing loss with a concomitant decrease in the level of the distortion product ld results of the comparison between fm pf and dpoae i o parameters revealed only a weak correlation suggesting that one or both of these measures may p

global cauchy problem for the ostrovsky equation abstract in this article we consider the initial value problem for the ostrovsky equation t u x 3 u x 1 u u x u 0 x r t r u x 0 u 0 x with initial data in sobolev spaces h s r using bourgain spaces we prove that the problem is globally well posed for s 3 10 for both signs in the equation

cochlear nonlinearity in normal hearing subjects as inferred psychophysically and from distortion product otoacoustic emissions the aim was to investigate the correlation between estimates of compression ratio compression threshold and cochlear gain for normal hearing subjects inferred from temporal masking curves tmc and distortion product otoacoustic emission dpoaes input output i o curves special care was given to reduce the influence of dpoae fine structure on the i o curves data were collected for 10 subjects and for cochlear places with characteristic frequencies cfs of 0 5 1 2 and 4 khz except at 4 khz little correlation was found between ratio estimates obtained with the two methods one reason is that the dpoae i o curves show plateaus or dips which result in unexpectedly high compression estimates moderately high correlation was found between the compression threshold estimates obtained with the two methods although dpoae based values were systematically lower than those based on the tmcs both methods confirmed that compression ratio and threshold are approximately constant across the cf range considered cochlear gain could be estimated from tmcs only and it was found to increase slightly with increasing cf it is discussed that dpoae i o curves may be inappropriate to infer precise individual nonlinear cochlear characteristics in normal hearing listeners particularly at low cfs work supported by imserso 131 06 profit cit 390000 2005 4 mec bfu 2006 07536 and the oticon foundation

age related differences in discrimination of an interval separating onsets of successive tone bursts as a function of interval duration the study measured listener sensitivity to increments in the inter onset interval ioi separating pairs of successive 20 ms 4000 hz tone pulses a silent interval between the tone pulses was adjusted across conditions to create reference tonal ioi values of 25 600ms for each condition a duration dl for increments of the tonal ioi was measured in listeners comprised of young normal hearing adults and two groups of older adults with and without high frequency hearing loss discrimination performance of all listeners was poorest for the shorter reference iois and improved to stable levels for longer reference intervals exceeding about 200ms temporal sensitivity of the young listeners was significantly better than that of the elderly listeners in each condition with the largest age related differences observed for the shortest reference interval age related differences were also observed for duration dls measured using single 4000 hz tone bursts set to three reference durations in the range 50 200ms t

the deterioration of hearing with age frequency selectivity the critical ratio the audiogram and speech threshold the frequency selectivity of the auditory system was measured by masking a sinusoidal signal 0 5 2 0 or 4 0 khz or a filtered speech signal with a wideband noise having a notch or stopband centered on the signal as the notch was widened performance improved for both types of signal but the rate of improvement decreased as the age of the 16 listeners increased from 23 to 75 years indicating a loss in frequency selectivity with age auditory filter shapes derived from the tone in noise data show a that the passband of the filter broadens progressively with age and b that the dynamic range of the filter ages like the audiogram that is the range changes little with age before 55 but beyond this point there is an accelerating rate of loss the speech experiment shows comparable but smaller effects the filter width measurements show that the critical ratio is a poor estimator of frequency selectivity because it confounds the tuning of the system with the efficiency of the signal detection and speech processing mechanisms that follow the filter an alternative one point measure of frequency selectivity which is both sensitive and reliable is developed via the filter shape model of masking

modified trif s functional equations in banach modules over a c algebra and approximate algebra homomorphisms abstract we prove the hyers ulam rassias stability of modified trif s functional equations in banach modules over a unital c algebra it is applied to show the stability of banach algebra homomorphisms between banach algebras associated with modified trif s functional equations in banach algebras

the importance of temporal fine structure information in speech at different spectral regions for normal hearing and hearing impaired subjects speech reception thresholds srts were measured for target and competing speech signals processed to contain variable amounts of temporal fine structure tfs information signals were filtered into 30 1 erb n wide channels where erb n refers to the bandwidth of normal auditory filters which were either tone vocoded preserving temporal envelope information extracted using the hilbert transform or left unprocessed containing both tfs and envelope information improvements in srt were compared when tfs was progressively introduced starting with the high or low frequency channels the results suggest some redundancy in the tfs information across frequency regions in a second experiment the signal was divided into five 6 erb n wide spectral regions four of which were tone vocoded the remaining region was either absent creating a spectral notch or was present and unprocessed srts were measured for normal hearing and hearing impaired subjects conditions where all channels were vocoded or unprocessed were also included normal hearing subjects benefited similarly when tfs information was added to each region suggesting that tfs information is important over a wide frequency range hearing impaired subjects benefited less although the benefit varied across subjects benefit from tfs information in speech was correlated with a psychophysical measure of tfs sensitivity obtained at two center frequencies

characterizing auditory processing and perception in individual listeners with sensorineural hearing loss this study considered consequences of sensorineural hearing loss in ten listeners the characterization of individual hearing loss was based on psychoacoustic data addressing audiometric pure tone sensitivity cochlear compression frequency selectivity temporal resolution and intensity discrimination in the experiments it was found that listeners with comparable audiograms can show very different results in the supra threshold measures in an attempt to account for the observed individual data a model of auditory signal processing and perception jepsen et al j acoust soc am 124 422 438 2008 was used as a framework the parameters of the cochlear processing stage of the model were adjusted to account for behaviorally estimated individual basilar membrane input output functions and the audiogram from which the amounts of inner hair cell and outer hair cell losses were estimated as a function of frequency all other model parameters were left unchanged the predictions showed a reasonably good agreement with the measured individual data in the frequency selectivity and forward masking conditions while the variation of intensity discrimination thresholds across listeners was underestimated by the model the model and the associated parameters for individual hearing impaired listeners might be useful for investigating effects of individual hearing impairment in more complex conditions such as speech intelligibility in noise

on and off frequency compression estimated using a new version of the additivity of forward masking technique on and off frequency compression at the 4000 and 8000 hz cochlear places were estimated using a new version of the additivity of forward masking afm technique that measures the effects of combining two non overlapping forward maskers instead of measuring signal thresholds to estimate compression of the signal as in the original afm technique the decrease in masker threshold in the combined masker condition compared to the individual masker conditions is used to estimate compression of the masker at the signal place by varying masker frequency it is possible to estimate off frequency compression the maskers were 500 hz wide bands of noise and the signal was a brief pure tone compression at different levels was estimated using different overall signal levels or different masker signal intervals it was shown that the new afm technique and the original afm technique produce consistent results considerable compression was observed for maskers well below the signal frequency suggesting that the assumption of off frequency linearity used in other techniques may not be valid reducing the duration of the first masker from 200 to 20 ms reduced the compression exponent in some cases suggesting a possible influence of olivocochlear efferent activity

comparing different estimates of cochlear compression in listeners with normal and impaired hearing a loss of cochlear compression may underlie many of the difficulties experienced by hearing impaired listeners two behavioral forward masking paradigms that have been used to estimate the magnitude of cochlear compression are growth of masking gom and temporal masking tm the aim of this study was to determine whether these two measures produce within subjects results that are consistent across a range of signal frequencies and if so to compare them in terms of reliability or efficiency gom and tm functions were measured in a group of five normal hearing and five hearing impaired listeners at signal frequencies of 1000 2000 and 4000 hz compression values were derived from the masking data and confidence intervals were constructed around these estimates both measures produced comparable estimates of compression but both measures have distinct advantages and disadvantages so that the more appropriate measure depends on factors such as the frequency region of interest and the degree of hearing loss because of the long testing times needed neither measure is suitable for clinical use in its current form

on the support of solutions to the ostrovsky equation with negative dispersion abstract in this article we prove that sufficiently smooth solutions of the ostrovsky equation with negative dispersion t u x 3 u x 1 u u x u 0 that have compact support for two different times are identically zero

variational problem of some quadratic functionals in complex analysis suppose we are given a pair of marked closed riemann surfacess twith the same genus we minimize the modified dirichlet integral for mappings ofsontot which is endowed with some weight in terms of conformal metric on the target surfacet in this paper it is demonstrated that the minimal harmonic map exists and it proves to be teichmuller

effect of amplitude modulation coherence for masked speech signals filtered into narrow bands introduction of masker amplitude modulation am can improve signal detection in a number of paradigms in some cases this advantage depends on the coherence of modulation across a relatively wide frequency range in the experiments described below observers were asked to identify masked spondee words produced by a single male talker the target spondees and masking noise were filtered into nine narrow bands and the coherence of am of either the speech signal or noise masker was manipulated inherent modulation of the masker bands was manipulated via assignment of real and imaginary values to the associated components of each band in the frequency domain and am of speech bands was achieved via multiplication with envelopes extracted from these maskers responses were based on two alternatives four alternatives or open response sets the effect of masker am coherence was highly dependent upon the size of the response set coherent am was associated with better thresholds in a two alternative response set but poorer thresholds in an open response set results with am speech did not depend critically upon the across frequency temporal synchrony of am imposed on the speech material

comparison of the roex and gammachirp filters as representations of the auditory filter although the rounded exponential roex filter has been successfully used to represent the magnitude response of the auditory filter recent studies with the roex p w t filter reveal two serious problems the fits to notched noise masking data are somewhat unstable unless the filter is reduced to a physically unrealizable form and there is no time domain version of the roex p w t filter to support modeling of the perception of complex sounds this paper describes a compressive gammachirp cgc filter with the same architecture as the roex p w t which can be implemented in the time domain the gain and asymmetry of this parallel cgc filter are shown to be comparable to those of the roex p w t filter but the fits to masking data are still somewhat unstable the roex p w t and parallel cgc filters were also compared with the cascade cgc filter patterson et al j acoust soc am 114 1529 1542 2003 which was found to provide an equivalent fit with 25 fewer coefficients moreover the fits were stable the advantage of the cascade cgc filter appears to derive from its parsimonious representation of the high frequency side of the filter it is concluded that cgc filters offer better prospects than roex filters for the representation of the auditory filter

the effects of age and cochlear hearing loss on temporal fine structure sensitivity frequency selectivity and speech reception in noise temporal fine structure tfs sensitivity frequency selectivity and speech reception in noise were measured for young normal hearing nhy old normal hearing nho and hearing impaired hi subjects two measures of tfs sensitivity were used the tfs lf test interaural phase difference discrimination and the tfs2 test discrimination of harmonic and frequency shifted tones these measures were not significantly correlated with frequency selectivity after partialing out the effect of audiometric threshold suggesting that insensitivity to tfs cannot be wholly explained by a broadening of auditory filters the results of the two tests of tfs sensitivity were significantly but modestly correlated suggesting that performance of the tests may be partly influenced by different factors the nho group performed significantly more poorly than the nhy group for both measures of tfs sensitivity but not frequency selectivity suggesting that tfs sensitivity declines with age in the absence of elevated audiometric thresholds or broadened auditory filters when the effect of mean audiometric threshold was partialed out speech reception thresholds in modulated noise were correlated with tfs2 scores but not measures of frequency selectivity or tfs lf test scores suggesting that a reduction in sensitivity to tfs can partly account for the speech perception difficulties experienced by hearing impaired subjects

phoneme recognition in vocoded maskers by normal hearing and aided hearing impaired listeners this study compared modulation benefit for phoneme recognition obtained by normal hearing nh and aided hearing impaired hi listeners consonant and vowel recognition scores were measured using nonsense syllables in the presence of a steady state noise and four vocoded speech maskers vocoded maskers were generated by modulating the steady state noise in either one or six frequency channels with the speech envelope extracted from the speech of either a single talker or a four talker babble aided hi listeners obtained lower consonant recognition scores than nh listeners in all masker conditions vowel recognition scores for aided hi listeners were comparable to nh scores except in the six channel vocoded masker conditions where they were relatively lower analysis using the extended speech intelligibility index developed by rhebergen versfeld and dreschler 2006 j acoust soc am 120 6 3988 3997 suggested that the signal to noise ratio deficit observed in aided hi listeners was largely due to uncompensated audibility loss there was no significant difference between modulation masking release obtained by nh and aided hi listeners for both consonant and vowel recognition

temporal modulation transfer functions for listeners with real and simulated hearing loss a functional simulation of hearing loss was evaluated in its ability to reproduce the temporal modulation transfer functions tmtfs for nine listeners with mild to profound sensorineural hearing loss each hearing loss was simulated in a group of three age matched normal hearing listeners through spectrally shaped masking noise or a combination of masking noise and multiband expansion tmtfs were measured for both groups of listeners using a broadband noise carrier as a function of modulation rate in the range 2 to 1024 hz the tmtfs were fit with a lowpass filter function that provided estimates of overall modulation depth sensitivity and modulation cutoff frequency although the simulations were capable of accurately reproducing the threshold elevations of the hearing impaired listeners they were not successful in reproducing the tmtfs on average the simulations resulted in lower sensitivity and higher cutoff frequency than were observed in the tmtfs of the hearing impaired listeners discrepancies in performance between listeners with real and simulated hearing loss are possibly related to inaccuracies in the simulation of recruitment

lie homomorphisms between lie c algebras and lie derivations on lie c algebras abstract we prove the generalized hyers ulam rassias stability of lie homomorphisms in lie c algebras and of lie derivations on lie c algebras

comparison of frequency selectivity and consonant recognition among hearing impaired and masked normal hearing listeners frequency selectivity and consonant recognition were determined for normal hearing and hearing impaired listeners using techniques that facilitate comparisons of performance among listeners whose absolute thresholds vary in magnitude and configuration first for each of six subjects with cochlear hearing loss masked thresholds in notched noise and narrow band noise maskers were obtained and compared to results for three normal hearing listeners whose thresholds were precisely matched to the impaired listeners by masking with spectrally shaped broadband noise second for hearing impaired listeners and their masked normal hearing controls measurements of consonant recognition were obtained at several speech presentation levels selected on the basis of articulation index predictions to assure equal speech spectrum audibility across listeners the results suggest that frequency selectivity is poorer for hearing impaired listeners than for masked normal hearing listeners even when thresholds among subjects are equated but the deviation from normal frequency selectivity is smaller than estimated from comparisons with normal hearing listeners in quiet critical ratios for hearing impaired listeners are equivalent to normal although frequency selectivity is reduced there is no consistent difference in consonant recognition between hearing impaired subjects and masked normal hearing subjects when performance is assessed under conditions that assure equal speech spectrum audibility across subjects

towards a measure of auditory filter phase response this study investigates how the phase curvature of the auditory filters varies with center frequency cf and level harmonic tone complex maskers were used with component phases adjusted using a variant of an equation proposed by schroeder ieee trans inf theory 16 85 89 1970 in experiment 1 the phase curvature of the masker was varied systematically and sinusoidal signal thresholds were measured at frequencies from 125 to 8000 hz at all signal frequencies threshold differences of 20 db or more were observed between the most effective and least effective masker phase curvature in experiment 2 the effect of overall masker level on masker phase effects was studied using signal frequencies of 250 1000 and 4000 hz the results were used to estimate the phase curvature of the auditory filters the estimated relative phase curvature decreases dramatically with decreasing cf below 1000 hz at frequencies above 1000 hz relative auditory filter phase curvature increases only slowly with increasing cf or may remain constant the phase curvature of the auditory filters seems to be broadly independent of overall level most aspects of the data are in qualitative agreement with peripheral physiological findings from other mammals which suggests that the phase responses observed here are of peripheral origin however in contrast to the data reported in a cat auditory nerve study carney et al j acoust soc am 105 2384 2391 1999 no reversal in the sign of the phase curvature was observed at very low frequencies overall the results provide a framework for mapping out the phase curvature of the auditory filters and provide constraints on future models of peripheral filtering in the human auditory system

on the support of solutions to the ostrovsky equation with positive dispersion abstract in this paper we prove that sufficiently smooth solutions of the ostrovsky equation with positive dispersion t u x 3 u x 1 u u x u 0 that have exponential decay for x 0 and such that their supports for two different times are contained in an interval b are identically zero

behavioral measures of cochlear compression and temporal resolution as predictors of speech masking release in hearing impaired listeners hearing impaired hi listeners often show less masking release mr than normal hearing listeners when temporal fluctuations are imposed on a steady state masker even when accounting for overall audibility differences this difference may be related to a loss of cochlear compression in hi listeners behavioral estimates of compression using temporal masking curves tmcs were compared with mr for band limited 500 4000 hz speech and pure tones in hi listeners and age matched noise masked normal hearing nmnh listeners compression and pure tone mr estimates were made at 500 1500 and 4000 hz the amount of mr was defined as the difference in performance between steady state and 10 hz square wave gated speech shaped noise in addition temporal resolution was estimated from the slope of the off frequency tmc no significant relationship was found between estimated cochlear compression and mr for either speech or pure tones nmnh listeners had significantly steeper off frequency temporal masking recovery slopes than did hi listeners and a small but significant correlation was observed between poorer temporal resolution and reduced mr for speech the results suggest either that the effects of hearing impairment on mr are not determined primarily by changes in peripheral compression or that the tmc does not provide a sufficiently reliable measure of cochlear compression

hyers ulam rassias stability of homomorphisms in quasi banach algebras associated to the pexiderized cauchy functional equation abstract in this paper we prove the hyers ulam rassias stability of homomorphisms in quasi banach algebras associated to the pexiderized cauchy functional equation this is applied to investigate homomorphisms between quasi banach algebras the concept of hyers ulam rassias stability originated from th m rassias stability theorem that appeared in his paper th m rassias on the stability of the linear mapping in banach spaces proc amer math soc 72 1978 297 300

relations among some psychoacoustic parameters in normal and cochlearly impaired listeners frequency resolution viz masking by low pass filtered noise and broadband noise and temporal resolution viz masking by interrupted noise were compared with hearing thresholds and acoustic reflex thresholds for four normally hearing and 13 cochlearly impaired subjects two models one for frequency resolution model i and one for temporal resolution model ii were introduced and these provided a means of predicting individual frequency and temporal resolution from hearing thresholds for both normal hearing and hearing impaired listeners model i is based on the assumption that the upward spread of masking increases in cochlearly impaired hearing with an amount proportional to the hearing threshold in db hl model ii is based on the assumption that the poststimulatory masked thresholds return to the level of the hearing threshold within a duration of 200 ms independent of the level of the masker and the amount of cochlear hearing loss model parameters were determined from results from other st

masking release for hearing impaired listeners the effect of increased audibility through reduction of amplitude variability the masking release i e better speech recognition in fluctuating compared to continuous noise backgrounds observed for normal hearing nh listeners is generally reduced or absent in hearing impaired hi listeners one explanation for this lies in the effects of reduced audibility elevated thresholds may prevent hi listeners from taking advantage of signals available to nh listeners during the dips of temporally fluctuating noise where the interference is relatively weak this hypothesis was addressed through the development of a signal processing technique designed to increase the audibility of speech during dips in interrupted noise this technique acts to i compare short term and long term estimates of energy ii increase the level of short term segments whose energy is below the average energy and iii normalize the overall energy of the processed signal to be equivalent to that of the original long term estimate evaluations of this energy equalizing eeq technique included consonant identification and sentence reception in backgrounds of continuous and regularly interrupted noise for hi listeners performance was generally similar for processed and unprocessed signals in continuous noise however superior performance for eeq processing was observed in certain regularly interrupted noise backgrounds

moderate cochlear hearing loss leads to a reduced ability to use temporal fine structure information the ability of normally hearing and hearing impaired subjects to use temporal fine structure information in complex tones was measured subjects were required to discriminate a harmonic complex tone from a tone in which all components were shifted upwards by the same amount in hz in a three alternative forced choice task the tones either contained five equal amplitude components non shaped stimuli or contained many components but were passed through a fixed bandpass filter to reduce excitation pattern changes shaped stimuli components were centered at nominal harmonic numbers n 7 11 and 18 for the shaped stimuli hearing impaired subjects performed much more poorly than normally hearing subjects with most of the former scoring no better than chance when n 11 or 18 suggesting that they could not access the temporal fine structure information performance for the hearing impaired subjects was significantly improved for the non shaped stimuli presumably because they could benefit from spectral cues it is proposed that normal hearing subjects can use temporal fine structure information provided the spacing between fine structure peaks is not too small relative to the envelope period but subjects with moderate cochlear hearing loss make little use of temporal fine structure information for unresolved components

revision extension and evaluation of a binaural speech intelligibility model this study presents revision extension and evaluation of a binaural speech intelligibility model beutelmann r and brand t 2006 j acoust soc am 120 331 342 that yields accurate predictions of speech reception thresholds srts in the presence of a stationary noise source at arbitrary azimuths and in different rooms the modified model is based on an analytical expression of binaural unmasking for arbitrary input signals and is computationally more efficient while maintaining the prediction quality of the original model an extension for nonstationary interferers was realized by applying the model to short time frames of the input signals and averaging over the predicted srt results binaural srts from 8 normal hearing and 12 hearing impaired subjects incorporating all combinations of four rooms three source setups and three noise types were measured and compared to the model s predictions depending on the noise type the parametric correlation coefficients between observed and predicted srts were 0 80 0 93 for normal hearing subjects and 0 59 0 80 for hearing impaired subjects the mean absolute prediction error was 3 db for the mean normal hearing data and 4 db for the individual hearing impaired data 70 of the variance of the srts of hearing impaired subjects could be explained by the model which is based only on the audiogram

approximate homomorphisms on jb triples abstract it is shown that for an approximate homomorphism f j b of a jb triple j into a jb triple b there exists a unique homomorphism h j b near the approximate homomorphism

effects of spectral smearing and temporal fine structure degradation on speech masking release this study assessed the effects of spectral smearing and temporal fine structure tfs degradation on masking release mr the improvement in speech identification in amplitude modulated compared to steady noise observed for normal hearing listeners syllables and noise stimuli were processed using either a spectral smearing algorithm or a tone excited vocoder the two processing schemes simulated broadening of the auditory filters by factors of 2 and 4 simulations of the early stages of auditory processing showed that the two schemes produced comparable excitation patterns however fundamental frequency f0 information conveyed by tfs was degraded more severely by the vocoder than by the spectral smearing algorithm both schemes reduced mr but for each amount of spectral smearing the vocoder produced a greater reduction in mr than the spectral smearing algorithm consistent with the effects of each scheme on f0 representation moreover the effects of spectral smearing on mr produced by the two schemes were different for manner and voicing finally mr data for listeners with moderate hearing loss were well matched by mr data obtained for normal hearing listeners with vocoded stimuli suggesting that impaired frequency selectivity alone may not be sufficient to account for the reduced mr observed for hearing impaired listeners