Exploration of a physiologically-inspired hearing-aid algorithm using a computer model mimicking impaired hearing

Objective: To use a computer model of impaired hearing to explore the effects of a physiologically-inspired hearing-aid algorithm on a range of psychoacoustic measures. Design: A computer model of a hypothetical impaired listener’s hearing was constructed by adjusting parameters of a computer model of normal hearing. Absolute thresholds, estimates of compression, and frequency selectivity (summarized to a hearing profile) were assessed using this model with and without pre-processing the stimuli by a hearing-aid algorithm. The influence of different settings of the algorithm on the impaired profile was investigated. To validate the model predictions, the effect of the algorithm on hearing profiles of human impaired listeners was measured. Study sample: A computer model simulating impaired hearing (total absence of basilar membrane compression) was used, and three hearing-impaired listeners participated. Results: The hearing profiles of the model and the listeners showed substantial changes when the test stimuli were pre-processed by the hearing-aid algorithm. These changes consisted of lower absolute thresholds, steeper temporal masking curves, and sharper psychophysical tuning curves. Conclusion: The hearing-aid algorithm affected the impaired hearing profile of the model to approximate a normal hearing profile. Qualitatively similar results were found with the impaired listeners’ hearing profiles.     

Relations between psychophysical measures of spatial hearing and self-reported spatial-hearing abilities

Objective: The aim of the present study was to investigate how well the virtual psychophysical measures of spatial hearing from the preliminary auditory profile predict self-reported spatial-hearing abilities. Design: Virtual spatial-hearings tests (conducted unaided, via headphones) and a questionnaire were administered in five centres in Germany, the Netherlands, Sweden, and the UK. Correlations and stepwise linear regression models were calculated among a group of hearing-impaired listeners. Study sample: Thirty normal-hearing listeners aged 19–39 years, and 72 hearing-impaired listeners aged 22–91 years with a broad range of hearing losses, including asymmetrical and mixed hearing losses. Results: Several significant correlations (between 0.24 and 0.54) were found between results of virtual psychophysical spatial-hearing tests and self-reported localization abilities. Stepwise linear regression analyses showed that the minimum audible angle (MAA) test was a significant predictor for self-reported localization abilities (5% extra explained variance), and the spatial speech reception threshold (SRT) benefit test for self-reported listening to speech in spatial situations (6% extra explained variance). Conclusions: The MAA test and spatial SRT benefit test are indicative measures of everyday binaural functioning. The binaural SRT benefit test was not found to predict self-reported spatial-hearing abilities.     

Evaluation of the preliminary auditory profile test battery in an international multi-centre study

Abstract

Objective: This paper describes the composition and international multi-centre evaluation of a battery of tests termed the preliminary auditory profile. It includes measures of loudness perception, listening effort, speech perception, spectral and temporal resolution, spatial hearing, self-reported disability and handicap, and cognition. Clinical applicability and comparability across different centres are investigated. Design: Headphone tests were conducted in five centres divided over four countries. Effects of test-retest, ear, and centre were investigated. Results for normally-hearing (NH) and hearing-impaired (HI) listeners are presented. Study sample: Thirty NH listeners aged 19–39 years, and 72 HI listeners aged 22–91 years with a broad range of hearing losses were included. Results: Test-retest reliability was generally good and there were very few right/left ear effects. Results of all tests were comparable across centres for NH listeners after baseline correction to account for necessary differences between test materials. For HI listeners, results were comparable across centres for the language-independent tests. Conclusions: The auditory profile forms a clinical test battery that is applicable in four different languages. Even after baseline correction, differences between test materials have to be taken into account when interpreting results of language-dependent tests in HI listeners.     

Development of a method for determining binaural sensitivity to temporal fine structure

Objective: To develop and evaluate a test of the ability to process binaural temporal-fine-structure (TFS) information. The test was intended to provide a graded measure of TFS sensitivity for all listeners. Design: Sensitivity to TFS was assessed at a sensation level of 30?dB using the established TFS-LF test at centre frequencies of 250, 500 and 750?Hz, and using the new TFS-AF test, in which the interaural phase difference (IPD) was fixed and the frequency was adaptively varied. IPDs varied from 30 to 180°. Study Sample: Nine young (19–25 years) and 23 older (47–84 years) listeners with normal hearing over the tested frequency range. Results: For the young listeners, thresholds on the TFS-AF test did not improve significantly with repeated testing. The rank-ordering of performance across listeners was independent of the size of the IPD, and moderate-to-strong correlations were observed between scores for the TFS-LF and TFS-AF tests. Older listeners who were unable to complete the TFS-LF test were all able to complete the TFS-AF test. Conclusions: No practice effects and strong correlations with an established test of binaural TFS sensitivity make the TFS-AF test a good candidate for the assessment of supra-threshold binaural processing.     

Evaluation of the effects of nonlinear frequency compression on speech recognition and sound quality for adults with mild to moderate hearing loss

Objective: While potentially improving audibility for listeners with considerable high frequency hearing loss, the effects of implementing nonlinear frequency compression (NFC) for listeners with moderate high frequency hearing loss are unclear. The purpose of this study was to investigate the effects of activating NFC for listeners who are not traditionally considered candidates for this technology. Design: Participants wore study hearing aids with NFC activated for a 3–4 week trial period. After the trial period, they were tested with NFC and with conventional processing on measures of consonant discrimination threshold in quiet, consonant recognition in quiet, sentence recognition in noise, and acceptableness of sound quality of speech and music. Study sample: Seventeen adult listeners with symmetrical, mild to moderate sensorineural hearing loss participated. Better ear, high frequency pure-tone averages (4, 6, and 8 kHz) were 60 dB HL or better. Results: Activating NFC resulted in lower (better) thresholds for discrimination of /s/, whose spectral center was 9 kHz. There were no other significant effects of NFC compared to conventional processing. Conclusion: These data suggest that the benefits, and detriments, of activating NFC may be limited for this population.     

Frequency compression hearing aid for severe-to-profound hearing impairments

(1) Objective: Objective of this study is to know how a frequency compression hearing aid with new concepts is beneficial for severe-to-profound hearing impairments. (2) Methods: Clinical trials of this hearing aid were conducted for 11 severe-to-profound hearing impaired listeners. These 11 wore the frequency compression hearing aid in their daily life and reported subjectively on its performance. Speech recognition tests with five listeners and audio-visual short sentence recognition tests with three listeners were also conducted. This hearing aid can separately adjust the fundamental frequency from the spectral envelope of input speech and can adjust frequency response by use of a post-processing digital filter. (3) Results: Five listeners out of these 11 came to prefer this hearing aid in their daily life and are still wearing it. The results of the speech recognition tests show that the speech recognition scores were not improved for all listeners and the results of the audio-visual short sentence recognition tests do that the audio-visual recognition scores were improved for two listeners. (4) Conclusion: There were some severe-to-profound hearing impaired listeners who preferred the frequency compression hearing aid finally. It is also suggested that the benefits of this hearing aid may be evaluated correctly using not only speech but also visual materials.     

Auditory brainstem and middle latency responses to 1 kHz tones in noise-masked normally-hearing and sensorineurally hearing-impaired adults

The present study provides comparative evaluation of the ABR and MLR to 1 kHz brief tones in two groups of hearing-impaired subjects (noise-masked normally-hearing; and sensorineurally hearing-impaired adults), as well as a normally-hearing control group. Tones were presented at intensities from threshold to 80–90 dB nHL. The results of this study show that: (1) the ABR and MLR to these low-frequency (1 kHz) tones are equally accurate in estimating hearing threshold, (2) at supra-threshold levels, there are differences in the ABRs and MLRs for subjects with decreased hearing sensitivity resulting from cochlear pathology, compared to those obtained from adults with simulated hearing loss due to broadband masking, and (3) supra-threshold stimuli produce differential effects on the latency and amplitude characteristics of the ABR and MLR in listeners with true sensorineural hearing impairments. Possible physiologic explanations are offered for this differential pattern of results.     

Auditory brainstem and middle latency responses to 1 khz tones in noise-masked normally-hearing and sensorineurally hearing-impaired adults

The present study provides comparative evaluation of the ABR and MLR to 1 kHz brief tones in two groups of hearing-impaired subjects (noise-masked normally-hearing; and sensorineurally hearing-impaired adults), as well as a normally-hearing control group. Tones were presented at intensities from threshold to 80-90 dB nHL. The results of this study show that: (1) the ABR and MLR to these low-frequency (1 kHz) tones are equally accurate in estimating hearing threshold, (2) at supra-threshold levels, there are differences in the ABRs and MLRs for subjects with decreased hearing sensitivity resulting from cochlear pathology, compared to those obtained from adults with simulated hearing loss due to broadband masking, and (3) supra-threshold stimuli produce differential effects on the latency and amplitude characteristics of the ABR and MLR in listeners with true sensorineural hearing impairments. Possible physiologic explanations are offered for this differential pattern of results.     

Speech perception in noise for bilingual listeners with normal hearing

Objective: The purpose of this study was to determine if speech-in-noise ability, as measured by SNR-50 and SNR loss in bilingual Spanish listeners with normal hearing, was affected by test difficulty. Design: Quasi-experimental, non-randomized intervention study. Study sample: Two groups of adult listeners participated: monolingual English listeners with normal hearing (N?=?12) and bilingual Spanish listeners with normal hearing who were proficient in English (N?=?10). The quick speech-in-noise (QuickSIN), the Bamford-Kowal-Bench speech-in-noise (BKB-SIN), and the words-in-noise (WIN) tests were used to assess signal-to-noise ratio (SNR) loss and SNR-50 for both groups. Results: Despite the fact that the bilinguals had normal hearing and were proficient in English, each of the speech-in-noise tests evaluated indicated the Spanish listeners had measurable SNR loss and higher than normal SNR-50s. Performance on the BKB-SIN was best for both groups, indicating test difficulty had a significant impact on speech perception in noise. Conclusions: Bilingual Spanish listeners with normal hearing exhibited a mild SNR loss comparable to that observed for a person with hearing loss. This decreased performance in noise requires an improved SNR for this population to reach a comparable level of comprehension to their monolingual English counterparts.     

Computational Modeling of Individual Differences in Behavioral Estimates of Cochlear Nonlinearities

Temporal masking curves (TMCs) are often used to estimate cochlear compression in individuals with normal and impaired hearing. These estimates may yield a wide range of individual differences, even among subjects with similar quiet thresholds. This study used an auditory model to assess potential sources of variance in TMCs from 51 listeners in Poling et al. [J Assoc Res Otolaryngol, 13:91–108 (2012)]. These sources included threshold elevation, the contribution of outer and inner hair cell dysfunction to threshold elevation, compression of the off-frequency linear reference, and detection efficiency. Simulations suggest that detection efficiency is a primary factor contributing to individual differences in TMCs measured in normal-hearing subjects, while threshold elevation and the contribution of outer and inner hair cell dysfunction are primary factors in hearing-impaired subjects. Approximating the most compressive growth rate of the cochlear response from TMCs was achieved only in subjects with the highest detection efficiency. Simulations included off-frequency nonlinearity in basilar membrane and inner hair cell processing; however, this nonlinearity did not improve predictions, suggesting that other sources, such as the decay of masking and the strength of the medial olivocochlear reflex, may mimic off-frequency nonlinearity. Findings from this study suggest that sources of individual differences can play a strong role in behavioral estimates of compression, and these sources should be considered when using forward masking to study cochlear function in individual listeners or across groups of listeners.     

The contribution of amplitude envelope cues to sentence identification in young and aged listeners

OBJECTIVE: The purpose of this study was to examine the importance of amplitude envelope cues to sentence identification for aged listeners. We also examined the effect of increasing alterations (i.e., compression ratio) and amount of available frequency content (i.e., number of channels) for this population. DESIGN: Thirty-six listeners were classified according to their age (35 or younger versus 65 and older) and hearing status (normal hearing versus hearing impaired). Within each hearing status, mean hearing threshold thresholds for the young and aged listeners were matched as closely as possible through 4 kHz to control for sensitivity differences across age, and all listeners passed a cognitive screening battery. Accuracy of synthetic sentence identification was measured using stimuli processed to restrict spectral information. Performance was measured as a function of age, hearing status, amount of spectral information, and degradation of the amplitude envelope (using fast-acting compression with compression ratios ranging from 1:1 to 5:1). RESULTS: Mean identification scores decreased significantly with increasing age, the presence of hear- c ing loss, the removal of spectral information, and with increasing distortion of the amplitude envelope (i.e., higher compression ratios). There was a consistent performance gap between young and aged listeners, regardless of the magnitude of change to the amplitude envelope. This suggests that some cue other than amplitude envelope variations is inaccessible to the aged listeners. CONCLUSIONS: Although aged listeners performed more poorly overall, they did not show greater susceptibility to alterations in amplitude-envelope cues, such as those produced by fast-acting amplitude compression systems. It is therefore unlikely that compression parameters such as attack and release time or compression ratio would need to be a differentially programmed for aged listeners. Instead, the data suggest two possibilities: aged listeners have difficulty accessing the fine-structure temporal cues present in speech, and/or performance is degraded by age-related loss of function at a central processing level.     

Going wireless and booth-less for hearing testing in industry

Abstract

Objective: To assess the test–retest variability of hearing thresholds obtained with an innovative, mobile wireless automated hearing-test system (WAHTS) with enhanced sound attenuation to test industrial workers at a worksite as compared to standardised automated hearing thresholds obtained in a mobile trailer sound booth. Design: A within-subject repeated-measures design was used to compare air-conducted threshold tests (500–8000?Hz) measured with the WAHTS in six workplace locations, and a third test using computer-controlled audiometry obtained in a mobile trailer sound booth. Ambient noise levels were measured in all test environments. Study sample: Twenty workers served as listeners and 20 workers served as operators. Results: On average, the WAHTS resulted in equivalent thresholds as the mobile trailer audiometry at 1000, 2000, 3000 and 8000?Hz and thresholds were within?±5?dB at 500, 4000 and 6000?Hz. Conclusions: Comparable performance may be obtained with the WAHTS in occupational audiometry and valid thresholds may be obtained in diverse test locations without the use of sound-attenuating enclosures.     

Reaction time to 1- and 4-kHz tones as a function of sensation level in listeners with normal hearing

OBJECTIVE: Measures of reaction time (RT) near threshold have been used to indicate whether listeners with hearing losses of primarily cochlear origin experience greater loudness at elevated thresholds than at normal thresholds. These measurements have been based on the assumption that RTs near threshold are not affected by stimulus frequency in the 1- to 4-kHz range. The present study tests this hypothesis. DESIGN: To gain an understanding of how RT is affected by frequency, RTs to 1- and 4-kHz tones were measured in 16 listeners with normal hearing across a wide range of sensation levels (SLs). RESULTS: Statistical analyses indicate that RTs are affected by frequency in some listeners. This effect is most common at low SLs but is also present at higher SLs. Learning effects could not account for the observed differences between RTs at the two frequencies. CONCLUSIONS: Although reaction time-especially at low levels-is affected by stimulus frequency in some listeners, the effect is not large enough to account for the differences in RTs measured in all listeners with impaired hearing in other studies.     

Introducing real-life listening features into the clinical test environment: Part I: Measuring the hearing performance and evaluating the listening effort of individuals with normal hearing

Objective: Controlled clinical test environments are very different from real-life listening situations in which speaker and background noise level variations can hinder a person’s ability to hear and follow conversations. This study was performed to evaluate the ability of people with normal hearing to follow a single speaker in the presence of background noise, and to explore relations between those measures and the listeners’ subjective assessments, listening effort, and sound quality judgements.

Methods: A group of adults with normal hearing were evaluated using the following battery of tests: (i) Roving Level Test, (ii) the Just Understanding Speech Test, (iii) Performance Perceptual Test, (iv) the Visual Analogue Scale to evaluate listening effort, and (iv) with a sound quality questionnaire.

Results: The results show that people with normal hearing tend to accurately estimate their hearing abilities, and both the listening effort required and speech recognition thresholds tend to increase with increasing background noise.

Discussion: Implementing a battery of tests that evaluate speech-in-noise listening abilities, listening effort, and subjective hearing perception might provide greater insight into hearing performance than traditional measures. Additionally, the data generated in this study can be used for comparison with measures obtained from hearing impaired and hearing device listeners, and as such, has the potential to guide counselling and rehabilitation to a range of clinical populations.

Conclusion: The examination of both the self-estimated and verified performance measurements in simulated real-life listening situations can provide audiologists with a comprehensive and realistic profile of a person’s hearing performance.     

Impact of frequency compression on music perception

Objective: To determine the effects of frequency compression on music perception, and the impact of previous music training and hearing status. It was hypothesized that lesser amounts of compression would be preferred, and that this pattern of preference would be more evident in the musically trained groups. Design: A paired-comparison paradigm was used. Subjects listened to pairs of musical passages as processed by a hearing aid with different frequency-compression settings. Subjects indicated their preferred passage and the strength of their preference. Study sample: Fifty-seven subjects divided in four groups, according to hearing status (normal hearing, mild-to-moderate hearing loss), and previous music experience (trained, not trained). Results: Subjects generally preferred the conditions with the lesser amount of compression. Listeners in the group with previous music training showed stronger preference for less compression than those without training, as did listeners with normal hearing when compared to subjects with hearing loss. Conclusions: Although less frequency compression was in general preferred, there was more variability in the comparisons involving the default settings for a 50-dB hearing loss (i.e. start frequency 4000 Hz, compression ratio 2.5:1) and no compression, suggesting that mild amounts of compression may not be detrimental to perceived sound quality.     

Exploration of stimulus-frequency otoacoustic emission suppression tuning in hearing-impaired listeners

Objective: Otoacoustic emissions (OAEs) can provide useful measures of tuning of auditory filters. We previously established that stimulus-frequency (SF) OAE suppression tuning curves (STCs) reflect major features of behavioral tuning (psychophysical tuning curves, PTCs) in normally-hearing listeners. Here, we aim to evaluate whether SFOAE STCs reflect changes in PTC tuning in cases of abnormal hearing. Design: PTCs and SFOAE STCs were obtained at 1 kHz and/or 4 kHz probe frequencies. For exploratory purposes, we collected SFOAEs measured across a wide frequency range and contrasted them to commonly measured distortion product (DP) OAEs. Study sample: Thirteen listeners with varying degrees of sensorineural hearing loss. Results: Except for a few listeners with the most hearing loss, the listeners had normal/nearly normal PTCs. However, attempts to record SFOAE STCs in hearing-impaired listeners were challenging and sometimes unsuccessful due to the high level of noise at the SFOAE frequency, which is not a factor for DPOAEs. In cases of successful measurements of SFOAE STCs there was a large variability in agreement between SFOAE STC and PTC tuning. Conclusions: These results indicate that SFOAE STCs cannot substitute for PTCs in cases of abnormal hearing, at least with the paradigm adopted in this study.     

The effect of presentation level and compression characteristics on sentence recognition in modulated noise

The effect of fast-acting compression on speech recognition in fully modulated (FUM) noise in listeners with normal and impaired hearing was investigated in two experiments We wanted to determine the relationships between the benefit from compression and some audiological factors. Furthermore, the sensitivity to changes in compression parameters was also evaluated. The results showed that two-thirds of the listeners performed worse with fast-acting compression than with linear processing. Normal-hearing listeners showed the most benefit from compression. A significant relationship was found between benefit from compression and speech-to-noise ratio at threshold (SNRT) in slightly modulated (SM) noise. Pure-tone threshold was found to be a weak predictor of benefit from compression. No relationship was found between benefit from compression and the release of masking for the FUM noise. The variability in the results across different compression parameters was related to SNRT in SM noise. The results suggest an inverse relationship between benefit from compression and the severity of the suprathreshold hearing loss     

Temporary threshold shift after nuclear magnetic resonance tomography

The third-octave band levels of the noises produced in a MR-imager (1.0 Tesla Magneton, Siemens) were measured. Corresponding sounds presented through earphones have been used in simulation experiments to produce in normal-hearing listeners a temporary threshold shift lasting several minutes. These effects could be verified objectively using otoacoustic emissions. The consequences especially for patients with already impaired hearing are discussed: ear protection is strongly recommended.