Brian Glasberg

• University of Cambridge

Objectives: To assess whether there are significant differences between speech scores for different hearing aid prescription methods, specifically DSL i/o, DSL V, and NAL-NL1, using age-appropriate closed- and open-set speech tests with young children, designed to avoid floor and ceiling effects. Design: Participants were 44 children with modera...

OBJECTIVES: To assess whether there are significant differences between speech scores for different hearing aid prescription methods, specifically DSL i/o, DSL V, and NAL-NL1, using age-appropriate closed- and open-set speech tests with young children, designed to avoid floor and ceiling effects. DESIGN: Participants were 44 children with moderate...

This article describes a model of loudness for time-varying sounds that incorporates the concept of binaural inhibition, namely, that the signal applied to one ear can reduce the internal response to a signal at the other ear. For each ear, the model includes the following: a filter to allow for the effects of transfer of sound through the outer an...

Acoustic signals pass through numerous transforms in the auditory system before perceptual attributes such as loudness and pitch are derived. However, relatively little is known as to exactly when these transformations happen, and where, cortically or sub-cortically, they occur. In an effort to examine this, we investigated the latencies and locati...

The summation of loudness across ears is often studied by measuring the level difference required for equal loudness (LDEL) of monaural and diotic sounds. Typically, the LDEL is ∼5-6 dB, consistent with the idea that a diotic sound is ∼1.5 times as loud as the same sound presented monaurally at the same level, as predicted by the loudness model of...

The summation of loudness across ears is often studied indirectly by measuring the level difference required for equal loudness (LDEL) of monaurally and diotically presented sounds. Typically, the LDEL is 5-6 dB, consistent with the idea that a diotic sound is about 1.5 times as loud as the same sound presented monaurally at the same level, as pred...

The possible role of frequency-shift detectors (FSDs) was assessed for a task measuring the ability to hear out individual "inner" partials in a chord with seven partials uniformly spaced on the ERBN-number (Cam) scale. In each of the two intervals in a trial, a pure-tone probe was followed by a chord. In one randomly selected interval, the frequen...

Fundamental frequency difference limens (F0DLs) were measured for a target harmonic complex tone with nominal fundamental frequency (F0) of 200 Hz, in the presence and absence of a harmonic masker with overlapping spectrum. The F0 of the masker was 0, ± 3, or ± 6 semitones relative to 200 Hz. The stimuli were bandpass filtered into three regions: 0...

Judgments of whether a sinusoidal probe is higher or lower in frequency than the closest partial ("target") in a multi-partial complex are improved when the target is pulsed on and off. These experiments explored the contribution of reduction in perceptual confusion and recovery from adaptation to this effect. In experiment 1, all partials except t...

The aim of this study was to develop a version of the threshold-equalizing noise (TEN) test for the diagnosis of dead regions for use with Etymotic ER-3A insert earphones. The use of such earphones is helpful when testing clients with asymmetric hearing loss or clients whose ear canals tend to collapse under the pressure of supra-aural headphones....

Sensitivity to temporal fine structure (TFS) at low frequencies may be adversely affected by hearing loss at high frequencies even when absolute thresholds at low frequencies are within the normal range. However, in several studies suggesting this, the effects of hearing loss and age were confounded. Here, interaural phase discrimination (IPD) thre...

A model for calculating auditory excitation patterns and loudness for steady sounds for normal hearing is extended to deal with cochlear hearing loss. The filters used in the model have a double ROEX-shape, the gain of the narrow active filter being controlled by the output of the broad passive filter. It is assumed that the hearing loss at each au...

The relationship between the ability to hear out partials in complex tones, discrimination of the fundamental frequency (F0) of complex tones, and frequency selectivity was examined for subjects with mild-to-moderate cochlear hearing loss. The ability to hear out partials was measured using a two-interval task. Each interval included a sinusoid fol...

A new method for calculating auditory excitation patterns and loudness for steady sounds is described. The method is based on a nonlinear filterbank in which each filter is the sum of a broad passive filter and a sharp active filter. All filters have a rounded-exponential shape. For each center frequency (CF), the gain of the active filter is contr...

The relationship between the ability to hear out partials in complex tones,discrimination of the fundamental frequency (F0) of complex tones, and frequency selectivity was examined for subjects with mild‐to‐moderate cochlear hearing loss. The ability to hear out partials was measured using a two‐interval task. Each interval included a sinusoid foll...

Thresholds (F0DLs) were measured for discrimination of the fundamental frequency (F0) of a group of harmonics (group B) embedded in harmonics with a fixed F0. Miyazono and Moore [(2009). Acoust. Sci. & Tech. 30, 383386] found a large training effect for tones with high harmonics in group B, when the harmonics were added in cosine phase. It is shown...

Moore and Glasberg [(2007). J. Acoust. Soc. Am. 121, 1604-1612] developed a model for predicting the loudness of dichotic sounds. The model gave accurate predictions of data in the literature, except for an experiment of Zwicker and Zwicker [(1991). J. Acoust. Soc. Am. 89, 756-764], in which sounds with non-overlapping spectra were presented to the...

The purpose of these experiments was to assess whether the detection of diotic 5 Hz "probe" modulation of a 4000 Hz sinusoidal carrier was influenced by binaural interaction of "masker" modulators presented separately to each ear and applied to the same carrier. A 50 Hz masker modulator was applied to one ear and the masker modulator applied to the...

Three studies are reported assessing the validity of AMTAS, an automated method for obtaining an audiogram, including air- and bone-conduction thresholds (stimuli delivered by a forehead-placed transducer) with masking noise presented to the non-test ear. In Study 1, six subjects at each of three sites were tested using manual audiometry by two aud...

Moore et al (1999b) described a procedure, CAMEQ, for the initial fitting of multi-channel compression hearing aids. The procedure was derived using a model of loudness perception for impaired hearing. We describe here the development of a new fitting method, CAMEQ2-HF, which differs from CAMEQ in the following ways: (1) CAMEQ2-HF gives recommended...

A dead region is a region in the cochlea where the inner hair cells and/or the auditory neurones are functioning very poorly, if at all. People who are being considered for a combination of a cochlear implant and a hearing aid typically have a dead region in the parts of the cochlea that normally respond to medium and high frequencies, but have som...

Bernstein and Oxenham [(2008). J. Acoust. Soc. Am. 124, 1653-1667] measured thresholds for discriminating the fundamental frequency, F0, of a complex tone that was passed through a fixed bandpass filter. They found that performance worsened when the F0 was decreased so that only harmonics above the tenth were audible. However, performance in this c...

This paper describes the relationship between the scores obtained in the Bamford, Kowal and Bench (BKB) sentence test and the Arthur Boothroyd (AB) word test in quiet for a group of 71 cochlear implant users. Each subject was tested at the same appointment and in the same environment during routine clinical appointments at the South of England Coch...

Eight subjects with bilateral sensorineural hearing losses took part in a trial comparing listening unaided with listening binaurally through two types of hearing aid, aid A and aid B. Both aids incorporated slow-acting automatic gain control (AGC) operating on the whole speech signal. However, aid A also incorporated two-channel syllabic compressi...

The audibility of partials was measured for complex tones with partials uniformly spaced on an ERB(N)-number scale. On each trial, subjects heard a sinusoidal "probe" followed by a complex tone. The probe was mistuned downwards or upwards (at random) by 3% or 4.5% from the frequency of one randomly selected partial in the complex (the "target"). Th...

When a complex tone contains many harmonics, its pitch is usually determined by harmonics in a restricted frequency region, called the "dominant region," which for fundamental frequencies (FOs) ≥ 100 Hz corresponds to low, resolved harmonics. We estimated the dominant region for tones with low FO, by measuring thresholds, FODLs, for detecting a cha...

Since the first description of tinnitus retraining therapy (TRT), clinicians have modified and customised the method of TRT in order to suit their practice and their patients. A simplified form of TRT is used at Ealing Primary Care Trust Audiology Department. Simplified TRT is different from TRT in the type and (shorter) duration of the counseling...

The tendency to hear a tone sequence as 2 or more streams (segregated) builds up, but a sudden change in properties can reset the percept to 1 stream (integrated). This effect has not hitherto been explored using an objective measure of streaming. Stimuli comprised a 2.0-s fixed-frequency inducer followed by a 0.6-s test sequence of alternating pur...

It is possible for auditory prostheses to provide amplification for frequencies above 6 kHz. However, most current hearing-aid fitting procedures do not give recommended gains for such high frequencies. This study was intended to provide information that could be useful in quantifying appropriate high-frequency gains, and in establishing the popula...

The dominant region for pitch was measured for complex tones with low fundamental frequency (F0=35 and 50 Hz). The tones contained 59 harmonics, added in cosine or random phase. The harmonics were split into two groups; group A containing harmonics 1‐K and group B containing harmonics (K+1)‐N. On each trial, two successive complex tones were presen...

A survey of data on the perception of binaurally presented sounds indicates that loudness summation across ears is less than perfect; a diotic sound is less than twice as loud as the same sound presented monaurally. The loudness model proposed by Moore et al. [J. Audio Eng. Soc. 45, 224-240 (1997)] determines the loudness of binaural stimuli by a s...

For normally hearing subjects, thresholds for discriminating the fundamental frequency (F0) of a complex tone, F0DLs, increase when the number of the lowest harmonic, N, is above eight. A previous study showed that F0DLs were affected by component phase for N above 7, and it was argued that the increase in F0DLs with increasing N reflects a loss of...

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 t...

The loudness model described by Moore et al. [J. Audio Eng. Soc. 45, 224-240 (1997)] forms the basis for a recent ANSI standard for the calculation of the loudness of steady sounds. However, the model does not give accurate predictions of the absolute thresholds published in a recent ISO standard. Here it is described how the assumed middle-ear tra...

The effect of level and frequency on the audibility of partials was measured for complex tones with partials uniformly spaced on an equivalent rectangular bandwidth (ERB(N)) number scale. On each trial, subjects heard a sinusoidal "probe" followed by a complex tone. The probe was mistuned downwards or upwards (at random) by 4.5% from the frequency...

The mechanisms underlying the detection of second-order amplitude modulation (AM) were explored. The detectability of second-order AM (fixed depth for each subject) was measured for first- and second-order modulation rates of 16 and 2 Hz, respectively (slow-rate pair), and 50 and 10 Hz, respectively (fast-rate pair), with no masker, a low-band modu...

The Cambridge loudnessmodel, which forms the basis for the new ANSI standard (ANSI S3.4‐2005), is similar in structure to loudnessmodels proposed earlier by Fletcher and by Zwicker, but differs in many of the details. The input signal to each ear is specified in terms of its spectrum, which may be defined in 1/3‐octave bands, or as the sum of a ser...

Thresholds for discriminating the fundamental frequency (FO) of a complex tone, FODLs, are small when low harmonics are present, but increase when the number of the lowest harmonic, N, is above eight. To assess whether the relatively small FODLs for N in the range 8-10 are based on (partly) resolved harmonics or on temporal fine structure informati...

A model for predicting the audibility of time-varying signals in background sounds is described. The model requires the calculation of time-varying excitation patterns for the signal and background, using the methods described elsewhere. A quantity called instantaneous partial loudness (IPL) is calculated from the excitation patterns. The estimates...

We compared two adaptive procedures for fitting a multi-channel compression hearing aid. "Camadapt" uses judgements of the loudness of speech stimuli and the tonal quality of music stimuli. "Eartuner" uses judgements of the loudness and clarity of speech stimuli with differing spectral characteristics. Sixteen new users of hearing aids were fitted...

Children have higher auditory backward masking (BM) thresholds than adults. One explanation for this is poor temporal resolution, resulting in difficulty separating brief or rapidly presented sounds. This implies that the auditory temporal window is broader in children than in adults. Alternatively, elevated BM thresholds in children may indicate p...

To develop a new version of the threshold-equalizing-noise (TEN) test for the diagnosis of dead regions, with levels calibrated in dB HL rather than dB SPL, and with levels corresponding to the dial readings on the audiometer. The spectral shape of the noise required to give equal masked thresholds at all frequencies, when expressed in dB HL, was d...

The influence of temporal cues on sequential stream segregation was investigated using five elderly hearing-impaired listeners. In experiment 1, an alternating pattern of A and B tones was used. Each tone was a harmonic complex with a 100-Hz fundamental, with one of three passbands (1250-2500, 1768-3636, or 2500-5000 Hz) and one of three component-...

Roberts et al. [J. Acoust. Soc. Am. 112, 2074-2085 (2002)] demonstrated that sequential stream segregation occurs with stimuli that differ only in phase spectrum. We investigated if this was partly due to differences in effective excitation level. Stimuli were harmonic complexes with a 100 Hz fundamental, 1250-2500 Hz passband, and cosine, alternat...

We previously described a model for loudness perception for people with cochlear hearing loss. However, that model is incompatible with our most recent and most satisfactory model of loudness for normal hearing. Here, we describe a loudness model that is applicable to both normal and impaired hearing. In contrast to our earlier model for impaired h...

The level of broadcast sound is usually limited to prevent overmodulation of the transmitted signal. To increase the loudness of broadcast sounds, especially commercials, fast-acting amplitude compression is often applied. This allows the root-mean-square (rms) level of the sounds to be increased without exceeding the maximum permissible peak level...

The effects of bandwidth and component phase on masking were investigated using 200-ms narrowband (1-ERB(N)) and broadband (5-ERB(N)) cosine-phase (CP) and random-phase (RP) harmonic complex maskers, centered at 1 or 6 kHz. A continuous notched-noise was used to restrict off-frequency listening. The masker fundamental frequency (F0) was 25 Hz. In e...

Physiological data suggest that the peak of the travelling wave on the basilar membrane evoked by a high-frequency sinusoid moves towards the base with increasing level. Previously, we used a forward-masking technique to provide evidence for a similar effect in humans at 4 and 6.5 kHz. In the present study, we used a similar technique to determine...

Peripheral-channeling theorists argue that differences in excitation pattern between successive sounds are necessary for stream segregation to occur. The component phases of complex tones comprising unresolved harmonics (F0=100 Hz) were manipulated to change pitch and timbre without changing the power spectrum. In experiment 1, listeners compared t...

Previously we described a model for calculating the loudness of steady sounds from their spectrum. Here a new version of the model is presented, which uses a waveform as its input. The stages of the model are as follows. (a) A finite impulse response filter representing transfer through the outer and middle ear. (b) Calculation of the short-term sp...

Physiological data suggest that the travelling wave on the basilar membrane evoked by a sinusoid of fixed frequency moves towards the base with increasing level. We describe two psychoacoustic experiments that attempted to provide evidence for and quantify the extent of such a shift in humans. In experiment 1, masking patterns were measured in forw...

The inherent amplitude fluctuations in narrow bands of noise may limit the ability to detect gaps in the noise; 'dips' in the noise may be confused with the gap to be detected. For people with cochlear hearing loss, loudness recruitment may effectively magnify the fluctuations and this could partly account for the reduced ability to detect gaps in...

Temporal modulation transfer functions were obtained using sinusoidal carriers for four normally hearing subjects and three subjects with mild to moderate cochlear hearing loss. Carrier frequencies were 1000, 2000 and 5000 Hz, and modulation frequencies ranged from 10 to 640 Hz in one-octave steps. The normally hearing subjects were tested using le...

This paper examines the influence of external and internal noise on the detection of increments and decrements in the level of sinusoidal pedestals. In experiment 1, the pedestals were presented either 18 dB above the masked threshold in broadband noise (condition 18-Masked) or 18 dB above the absolute threshold (condition 18-Abs). Pedestal frequen...

We have described a model for calculating the partial loudness of a steady signal in the presence of a steady background sound [Moore et al., J. Audio Eng. Soc. 45, 224-240 (1997)]. We have also described a model for calculating the loudness of time-varying signals [B. R. Glasberg and B. C. J. Moore, J. Audio Eng. Soc. 50, 331-342 (2002)]. These tw...

Second-order amplitude modulation (AM) can be detected despite the absence of a component at the second-order modulation frequency in the modulation spectrum. This may depend on the detection of a modulation component at the second-order frequency produced by nonlinearities in the auditory system, or on the detection of a ``beat'' at the output of...

Thresholds for detecting sinusoidal signals were measured as a function of the spectral width of a notch in a noise masker. The notch was positioned both symmetrically and asymmetrically around the signal frequency. The noise was designed to create equal excitation per ERB within its passbands (uniformly exciting noise), after allowing for the tran...

Hearing impairment may sometimes be associated with complete loss of inner hair cells (IHCs) over a certain region of the basilar membrane. We call this a 'dead region'. Amplification (using a hearing aid) over a frequency range corresponding to a dead region may not be beneficial and may even impair speech intelligibility. However, diagnosis of de...

This paper describes a laboratory-based comparison of the effectiveness of two formulae for fitting linear hearing aids, the NAL(R) formula and the Cambridge formula. The formulae prescribe the desired insertion gain as a function of frequency, based on the audiometric threshold. The two formulae have a similar rationale; both are based on the goal...

Psychometric functions for detecting increments or decrements in level of sinusoidal pedestals were measured for increment and decrement durations of 5, 10, 20, 50, 100, and 200 ms and for frequencies of 250, 1000, and 4000 Hz. The sinusoids were presented in background noise intended to mask spectral splatter. A three-interval, three-alternative p...

Four different compression algorithms were implemented in wearable digital hearing aids: (1) The slow-acting dual-front-end automatic gain control (AGC) system [B. C. J. Moore, B. R. Glasberg, and M. A. Stone, Br. J. Audiol. 25, 171-182 (1991)], combined with appropriate frequency response equalization, with a compression threshold of 63 dB sound p...

Van Schijndel et al. [J. Acoust. Soc. Am. 105, 3425-3435 (1999)] proposed that the auditory system partitions the spectro-temporal domain into frequency-time (f-t) windows and that the characteristics of these windows could be explored by measuring intensity discrimination for Gaussian-shaped tone pulses presented just above their detection thresho...

A model for predicting loudness for people with cochlear hearing loss is applied to the problem of the initial fitting of multi-channel fast-acting compression hearing aids. The fitting is based entirely on the pure tone audiogram, and does not require measures of loudness growth. One constraint is always applied: the specific loudness pattern evok...

This paper describes further tests of a model for loudness perception in people with cochlear hearing loss. It is assumed that the hearing loss (the elevation in absolute threshold) at each audiometric frequency can be partitioned into a loss due to damage to outer hair cells (OHCs) and a loss due to damage to inner hair cells (IHCs) and/or neurons...

This study examined whether "modulation masking" could be produced by temporal similarity of the probe and masker envelopes, even when the masker envelope did not contain a spectral component close to the probe frequency. Both masker and probe amplitude modulation were applied to a single 4-kHz sinusoidal or narrow-band noise carrier with a level o...

A model for predicting loudness for people with cochlear hearing loss was applied to the problem of the initial fitting of a multi-channel compression hearing aid. The fitting was based on two constraints: (1) The specific loudness pattern evoked by speech of a moderate level (65 dB SPL) should be reasonably flat (equal loudness per critical band),...

A model for predicting loudness for people with cochlear hearing loss is applied to the problem of prescribing the frequency-gain characteristic of a linear hearing aid. It is argued that a reasonable goal is to make all frequency bands of speech equally loud while achieving a comfortable overall loudness; this can maximize the proportion of the sp...

Hearing aids with multi-channel compression are often fitted on the basis of loudness scaling data obtained using narrow bands of noise or tones. Here, we report the development and evaluation of an alternative fitting procedure based on the use of speech signals. The parameters of the hearing aid (the gains in each channel for high and low input l...

Simulations of hearing impairment were presented to the normal ears of subjects with moderate to severe unilateral cochlear hearing loss. The intelligibility of speech in quiet and in background sounds was compared with that obtained for the impaired ears using unprocessed stimuli. The results of loudness matches between the two ears were used to t...

A loudness model for steady sounds is described having the following stages: 1) a fixed filter representing transfer through the outer ear; 2) a fixed filter representing transfer through the middle ear; 3) calculation of an excitation pattern from the physical spectrum; 4) transformation of the excitation pattern to a specific loudness pattern; 5)...

Thresholds for the detection of decrements in level of sinusoidal signals were measured as a function of duration (2, 4, 6, 10, and 14 ms), level (70, 80, and 90 dB SPL) and frequency (250, 500, 1000, 2000, and 4000 Hz). Seven normally hearing listeners were tested at each frequency. Thresholds for detecting a 10?ms increment in level were also mea...

Zwicker's loudness model has the following stages: (a) A fixed filter representing transfer through the outer and middle ear; (b) Calculation of an excitation pattern from the physical spectrum; (c) Transformation of the excitation pattern to a specific loudness pattern. The area under the specific loudness pattern is assumed to determine loudness....

In the probe-signal method, subjects are required to detect a signal in noise that is presented on the majority of trials at an "expected" (target) frequency but on a minority of trials at an "unexpected" probe frequency. Detection of the probes worsens with increasing separation between the target and probe frequencies. This result has often been...

This experiment simulated the threshold elevation and loudness recruitment associated with three different types of 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 isolatio...

Thresholds for the detection of decrements in level of sinusoidal signals were measured as a function of decrement duration, level (25, 40, 55, and 70 dB SPL) and frequency (250, 1000, and 4000 Hz) in eleven normally hearing subjects. Thresholds for detecting a brief increment in level were also measured. The sinusoids were presented in a backgroun...

The notched-noise method has been widely used to estimate the shape of the auditory filter. Results obtained using this method may be influenced by combination bands produced by the interaction of components within the upper band of noise in the notched-noise masker. To assess the possible effect of such combination bands, results were compared for...

Growth-of-masking functions were obtained for sinusoidal signals at three frequencies (fs), 0.25, 1.0, and 4.0 kHz, using maskers that were always higher in frequency than the signal. Five different maskers were used, chosen so as to evaluate the influence of temporal fluctuations in the maskers and of combination products produced by the interacti...

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,...

Thresholds for the detection of gaps in sinusoidal signals were measured as a function of frequency (100-2000 Hz) and level (25-85 dB SPL) in 11 normally hearing subjects. The sinusoids were presented in a background noise intended to mask spectral splatter associated with the gap. In a separate experiment, auditory filter shapes and detection effi...

This paper describes two experiments in a series evaluating and optimising a hearing aid incorporating two forms of automatic gain control (AGC). The first form is a front-end AGC which is normally slow acting and which compensates for variations in the overall level of speech from one situation to another. The second form of AGC follows the front-...

This study was undertaken in order to document, in a group of subjects affected by a noise-induced hearing loss, the relation between the loss of auditory sensitivity and the loss of frequency selectivity at mid-frequencies, namely 1000 and 3000 Hz. Auditory filter shapes were estimated using the notched noise method. Twelve notch widths were teste...

The shape of the auditory filter at a given centre frequency can be estimated by measuring the threshold for detecting a sinusoid presented in a spectral notch in a noise masker, as a function of notch width. Laboratory studies using this method have typically been based on threshold measurements for between 13 and 19 notch widths. In this note, we...

The inherent fluctuations present in narrowbands of noise may limit the ability to detect gaps in the noise, ‘dips/rs in the noise may be confused with the gap to be detected. For subjects with cochlear hearing loss, loudness recruitment may effectively magnify the fluctuations and this could partly account for the reduced ability to detect gaps in...

Thresholds for the detection of temporal gaps in sinusoidal signals were measured as a function of frequency (100-2000 Hz) and level in 15 elderly hearing-impaired subjects and 11 elderly subjects with near-normal hearing at frequencies below 2000 Hz. The sinusoids were presented in a background noise intended to mask spectral splatter associated w...

The accuracy of a method of simulating reduced frequency selectivity by the spectral smearing of complex stimuli has been evaluated. First an excitation pattern that would be evoked by a given nonsmeared stimulus in an impaired ear with broad auditory filters was estimated. Then the spectral smearing of the stimulus that would be necessary to creat...

The discrimination of the fundamental frequency (fo) of pairs of complex tones with no common harmonics is worse than the discrimination of fo for tones with all harmonics in common. These experiments were conducted to assess whether this effect is a result of pitch shifts between pairs of tones without common harmonics or whether it reflects influ...

This study examines a form of masking that can take place when the signal and masker are widely separated in frequency and cannot be explained in terms of the traditional concept of the auditory filter or critical band. We refer to this as across-channel masking. The task of the subject was to detect an increment in modulation depth of a 1000-Hz si...

This paper describes experiments evaluating and optimizing an automatic gain control system, called dual front-end AGC (abbreviated as D), intended for use in hearing aids. This system has two purposes: (1) to compensate for variations in the overall level of speech from one situation to another by slowly changing its gain; (2) to protect the user...

A well established method for estimating the shape of the auditory filter is based on the measurement of the threshold of a sinusoidal signal in a notched-noise masker, as a function of notch width. To measure the asymmetry of the filter, the notch has to be placed both symmetrically and asymmetrically about the signal frequency. In previous work s...

Auditory-filter shapes were estimated in normally hearing subjects for signal frequencies (fs) of 100, 200, 400, and 800 Hz using the notched-noise method [R. D. Patterson and I. Nimmo-Smith, J. Acoust. Soc. Am. 67, 229-245 (1980)]. Two noise bands, each 0.4fs wide, were used; they were placed both symmetrically and asymmetrically about the signal...

Auditory filter shapes were derived from notched-noise masking data at center frequencies of 8 kHz (for three spectrum levels, N0 = 20, 35, and 50 dB) and 10 kHz (N0 = 50 dB). In order to minimize variability due to earphone placement, insert earphones (Etymotic Research ER2) were used and individual earmolds were made for each subject. These earph...

These experiments address the following issues. (1) When two complex tones contain different harmonics, do the differences in timbre between them impair the ability to discriminate the pitches of the tones? (2) When two complex tones have only a single component in common, and that component is the most discriminable component in each tone, is the...

These experiments on across-channel masking (ACM) and comodulation masking release (CMR) were designed to extend the work of Grose and Hall [J. Acoust. Soc. Am. 85, 1276-1284 (1989)] on CMR. They investigated the effect of the temporal position of a brief 700-Hz signal relative to the modulation cycle of a 700-Hz masker 100% sinusoidally amplitude...

At speech-to-noise ratios between -3 and 6 dB, many hearing-impaired listeners have difficulty in understanding speech, but spectrograms reveal that the formant peaks of voiced speech and some of the spectral peaks associated with unvoiced speech stand out against the background noise. Our speech-enhancement process is based on the assumption that...

These experiments measure the ability to detect a change in the relative phase of a single component in a harmonic complex tone. Complex tones containing the first 20 harmonics of 50, 100, or 200 Hz, all at equal amplitude, were used. All of the harmonics except one started in cosine phase. The remaining harmonic started in cosine phase, but was sh...