An overview of the HASPI and HASQI metrics for predicting speech intelligibility and speech quality for normal hearing, hearing loss, and hearing aids.

Alterations of the speech signal, including additive noise and nonlinear distortion, can reduce speech intelligibility and quality. Hearing aids present an especially complicated situation since these devices may implement nonlinear processing designed to compensate for the hearing loss. Hearing-aid processing is often realized as time-varying multichannel gain adjustments, and may also include frequency reassignment. The challenge in designing metrics for hearing aids and hearing-impaired listeners is to accurately model the perceptual trade-offs between speech audibility and the nonlinear distortion introduced by hearing-aid processing. This paper focuses on the Hearing Aid Speech Perception Index (HASPI) and the Hearing Aid Speech Quality Index (HASQI) as representative metrics for predicting intelligibility and quality. These indices start with a model of the auditory periphery that can be adjusted to represent hearing loss. The peripheral model, the speech features computed from the model outputs, and the procedures used to fit the features to subject data are described. Examples are then presented for using the metrics to measure the effects of additive noise, evaluate noise-suppression processing, and to measure the differences among commercial hearing aids. Open questions and considerations in using these and related metrics are then discussed.

A comparison of speech intelligibility and subjective quality with hearing-aid processing in older adults with hearing loss.

OBJECTIVE: This study characterised the relationship between speech intelligibility and quality in listeners with hearing loss for a range of hearing-aid processing settings and acoustic conditions. DESIGN: Binaural speech intelligibility scores and quality ratings were measured for sentences presented in babble noise and processed through a hearing-aid simulation. The intelligibility-quality relationship was investigated by (1) assessing the effects of experimental conditions on each task; (2) directly comparing intelligibility scores and quality ratings for each participant across the range of conditions; and (3) comparing the association between signal envelope fidelity (represented by a cepstral correlation metric) and intelligibility and quality. STUDY SAMPLE: Participants were 15 adults (7 females; age range 59-81 years) with mild to moderately severe sensorineural hearing loss. RESULTS: Intelligibility and quality showed a positive association both with each other and with changes to signal fidelity introduced by the entire acoustic and signal-processing system including the additive noise and the hearing-aid output. As signal fidelity decreased, quality ratings changed at a slower rate than intelligibility scores. Individual psychometric functions were more variable for quality compared to intelligibility. CONCLUSIONS: Variability in the intelligibility-quality relationship reinforces the importance of measuring both intelligibility and quality in clinical hearing-aid fittings.

The Type of Noise Influences Quality Ratings for Noisy Speech in Hearing Aid Users.

Purpose The overall goal of the current study was to determine whether noise type plays a role in perceptual quality ratings. We compared quality ratings using various noise types and signal-to-noise ratio (SNR) ranges using hearing aid simulations to consider the effects of hearing aid processing features. Method Ten older adults with bilateral mild to moderately severe sensorineural hearing loss rated the sound quality of sentences processed through a hearing aid simulation and presented in the presence of five different noise types (six-talker babble, three-talker conversation, street traffic, kitchen, and fast-food restaurant) at four SNRs (3, 8, 12, and 20 dB). Results Everyday noise types differentially affected sound quality ratings even when presented at the same SNR: Kitchen and three-talker noises were rated significantly higher than restaurant, traffic, and multitalker babble, which were not different from each other. The effects of noise type were most pronounced at poorer SNRs. Conclusions The findings of this study showed that noise types differentially affected sound quality ratings. The differences we observed were consistent with the acoustic characteristics of the noise types. Noise types having lower envelope fluctuations yielded lower quality ratings than noise types characterized by sporadic high-intensity events at the same SNR.

Integrating a remote microphone with hearing-aid processing.

A remote microphone (RM) links a talker's microphone to a listener's hearing aids (HAs). The RM improves intelligibility in noise and reverberation, but the binaural cues necessary for externalization are lost. Augmenting the RM signal with synthesized binaural cues and early reflections enhances externalization, but interactions of the RM signal with the HA processing could reduce its effectiveness. These potential interactions were evaluated using RM plus HA processing in a realistic listening simulation. The HA input was the RM alone, the augmented RM signal, the acoustic inputs at the HA microphones, including reverberation measured using a dummy head, or a mixture of the augmented RM and acoustic input signals. The HA simulation implemented linear amplification or independent dynamic-range compression at the two ears and incorporated the acoustic effects of vented earmolds. Hearing-impaired listeners scored sentence stimuli for intelligibility and rated clarity, overall quality, externalization, and apparent source width. Using the RM improved intelligibility but reduced the spatial impression. Increasing the vent diameter reduced clarity and increased the spatial impression. Listener ratings reflect a trade-off between the attributes of clarity and overall quality and the attributes of externalization and source width that can be explained using the interaural cross correlation.

Externalization of remote microphone signals using a structural binaural model of the head and pinna.

In a remote microphone (RM) system, a talker speaks into a microphone and the signal is transmitted to the hearing aids worn by the hearing-impaired listener. A difficulty with remote microphones, however, is that the signal received at the hearing aid bypasses the head and pinna, so the acoustic cues needed to externalize the sound source are missing. The objective of this paper is to process the RM signal to improve externalization when listening through earphones. The processing is based on a structural binaural model, which uses a cascade of processing modules to simulate the interaural level difference, interaural time difference, pinna reflections, ear-canal resonance, and early room reflections. The externalization results for the structural binaural model are compared to a left-right signal blend, the listener's own anechoic head-related impulse response (HRIR), and the listener's own HRIR with room reverberation. The azimuth is varied from straight ahead to 90° to one side. The results show that the structural binaural model is as effective as the listener's own HRIR plus reverberation in producing an externalized acoustic image, and that there is no significant difference in externalization between hearing-impaired and normal-hearing listeners.

Using Objective Metrics to Measure Hearing Aid Performance.

OBJECTIVES: The performance of hearing aids is generally characterized by a small set of standardized measurements. The primary goals of these procedures are to measure basic aspects of the hearing aid performance and to ascertain that the device is operating properly. A more general need exists for objective metrics that can predict hearing aid outcomes. Such metrics must consider the interaction of all the signal processing operating in the hearing aid and must do so while also accounting for the hearing loss for which the hearing aid has been prescribed. This article represents a first step in determining the clinical applicability of the hearing aid speech perception index (HASPI) intelligibility and hearing aid speech quality index (HASQI) speech quality metrics. The goals of this article are to demonstrate the feasibility of applying these metrics to commercial hearing aids and to illustrate the anticipated range of measured values and identify implementation concerns that may not be present for conventional measurements. DESIGN: This article uses the HASPI intelligibility and HASQI speech quality metrics to measure the performance of commercial hearing aids. These metrics measure several aspects of the processed signal, including envelope fidelity, modifications of the temporal fine structure, and changes in the long-term frequency response, all in the context of an auditory model that reproduces the salient aspects of the peripheral hearing loss. The metrics are used to measure the performance of basic and premium hearing aids from three different manufacturers. Test conditions include the environmental factors of signal to noise ratio and presentation level, and the fitting configurations were varied to provide different degrees of processing from linear to aggressive nonlinear processing for two different audiograms. RESULTS: The results show that the metrics are capable of measuring statistically significant differences across devices and processing settings. HASPI and HASQI measure both audibility and nonlinear distortion in the devices, and conditions are identified where predicted intelligibility is high but predicted speech quality is substantially reduced. The external signal properties of signal to noise ratio and presentation level are both statistically significant. Hearing loss is significant for HASPI but not for HASQI, and degree of processing is significant for both metrics. A quadratic model for manufacturer showed large effect sizes for HASPI and HASQI, but basic versus premium hearing aid model is not significant. CONCLUSIONS: The results presented in this article represent a first step in applying the HASPI and HASQI metrics to commercial hearing aids. Modern hearing aids often use several different processing strategies operating simultaneously. The proposed metrics provide a way to predict the total effect of this processing, including algorithm interactions that may be missed by conventional measurement procedures. The measurements in this article show significant differences between manufacturers, processing settings, and adjustment for different hearing losses. No significant differences were found between basic and premium hearing aid models. Further research will be needed to determine the clinical relevance of these measurements and to provide target values appropriate for successful fittings.

Survey of Current Practice in the Fitting and Fine-Tuning of Common Signal-Processing Features in Hearing Aids for Adults.

BACKGROUND: Current guidelines for adult hearing aid fittings recommend the use of a prescriptive fitting rationale with real-ear verification that considers the audiogram for the determination of frequency-specific gain and ratios for wide dynamic range compression. However, the guidelines lack recommendations for how other common signal-processing features (e.g., noise reduction, frequency lowering, directional microphones) should be considered during the provision of hearing aid fittings and fine-tunings for adult patients. PURPOSE: The purpose of this survey was to identify how audiologists make clinical decisions regarding common signal-processing features for hearing aid provision in adults. RESEARCH DESIGN: An online survey was sent to audiologists across the United States. The 22 survey questions addressed four primary topics including demographics of the responding audiologists, factors affecting selection of hearing aid devices, the approaches used in the fitting of signal-processing features, and the strategies used in the fine-tuning of these features. STUDY SAMPLE: A total of 251 audiologists who provide hearing aid fittings to adults completed the electronically distributed survey. The respondents worked in a variety of settings including private practice, physician offices, university clinics, and hospitals/medical centers. DATA COLLECTION AND ANALYSIS: Data analysis was based on a qualitative analysis of the question responses. The survey results for each of the four topic areas (demographics, device selection, hearing aid fitting, and hearing aid fine-tuning) are summarized descriptively. RESULTS: Survey responses indicate that audiologists vary in the procedures they use in fitting and fine-tuning based on the specific feature, such that the approaches used for the fitting of frequency-specific gain differ from other types of features (i.e., compression time constants, frequency lowering parameters, noise reduction strength, directional microphones, feedback management). Audiologists commonly rely on prescriptive fitting formulas and probe microphone measures for the fitting of frequency-specific gain and rely on manufacturers' default settings and recommendations for both the initial fitting and the fine-tuning of signal-processing features other than frequency-specific gain. CONCLUSIONS: The survey results are consistent with a lack of published protocols and guidelines for fitting and adjusting signal-processing features beyond frequency-specific gain. To streamline current practice, a transparent evidence-based tool that enables clinicians to prescribe the setting of other features from individual patient characteristics would be desirable.

Author's Rebuttal to Smits et al. (2018), "Comment on 'Sensitivity of the Speech Intelligibility Index to the Assumed Dynamic Range' by Jin et al. (2017)".

Purpose: The purpose of this letter is to refute the comments written by Smits, Goverts, and Versfeld (2018). Method: Refutations to each issue including the fixed mathematical relationship between dynamic range (DR) and a fitting constant (Q value), deviating results for small DRs, and determination of Speech Intelligibility Index (SII) model parameters are described. Results: Although Smits et al. (2018) correctly identified several issues, those comments do not diminish the results of the original article (Jin, Kates, & Arehart, 2017) in providing new insights for the SII. Conclusions: Jin et al. (2017) clearly provided the impact of languages and DR on the SII, which was the main result of the study.

Using envelope modulation to explain speech intelligibility in the presence of a single reflection.

A single reflection is the simplest simulation of reverberation and provides insights into more complex scenarios of listening in rooms. This paper presents an analysis of the effects of a single reflection as its delay and intensity are systematically varied. The changes to the envelope modulations are analyzed using not only the traditional within-auditory-band analysis approach but also an across-band spectro-temporal analysis using cepstral correlation coefficients. The use of an auditory model allowed the extension of the simulations to include sensorineural hearing loss. Short delays did not interfere with the envelope modulations at low modulation rates (<16 Hz) and impact predicted intelligibility, while longer delays caused substantial distortion at these rates. The patterns of envelope modulation distortions caused by a single reflection were shown to be similar in models of normal hearing and hearing impairment.

Sensitivity of the Speech Intelligibility Index to the Assumed Dynamic Range.

Purpose: This study aims to evaluate the sensitivity of the speech intelligibility index (SII) to the assumed speech dynamic range (DR) in different languages and with different types of stimuli. Method: Intelligibility prediction uses the absolute transfer function (ATF) to map the SII value to the predicted intelligibility for a given stimuli. To evaluate the sensitivity of the predicted intelligibility to the assumed DR, ATF-transformed SII scores for English (words), Korean (sentences), and Mandarin (sentences) were derived for DRs ranging from 10 dB to 60 dB. Results: Increasing the assumed DR caused steeper ATFs for all languages. However, high correlation coefficients between predicted and measured intelligibility scores were observed for DRs from 20 dB to 60 dB for ATFs in English, Korean, and Mandarin. Conclusions: Results of the present study indicate that the intelligibility computed from the SII is not sensitive to the assumed DR. The 30-dB DR commonly used in computing the SII is thus a reasonable assumption that produces accurate predictions for different languages and different types of stimuli.

Does Language Matter When Using a Graphical Method for Calculating the Speech Intelligibility Index?

BACKGROUND: Graphical methods for calculating the speech intelligibility index (SII), such as the count-the-dot audiogram, are useful tools in quantifying how much weighted audibility is restored when amplification is used for individuals with hearing loss. The band-importance function (BIF), which is an important component of the SII, depends on the language. Thus, language may affect the prediction of weighted audibility using the graphical SII. PURPOSE: The purpose of this study was to apply language-specific BIFs to develop and compare graphical SIIs for English, Korean, and Mandarin. RESEARCH DESIGN: The graphical SIIs were developed and compared using a research design that applied and analyzed existing datasets. DATA COLLECTION AND ANALYSIS: Language-specific BIFs and dynamic ranges were used to derive graphical SIIs for English, Korean, and Mandarin. SII predictions were compared by calculating the language-specific predictions for the same audiometric configurations. RESULTS: The graphical SIIs for English, Korean, and Mandarin yielded different unaided and aided predictions for the same audiogram configurations. CONCLUSIONS: A graphical SII helps patients easily understand their weighted audibility for unaided and aided conditions; thus, it is a useful counseling tool in the clinic. The most accurate graphical SII's will, however, be based on a patient's spoken language.

Using Cognitive Screening Tests in Audiology.

PURPOSE: The population of the United States is aging. Those older adults are living longer than ever and have an increased desire for social participation. As a result, audiologists are likely to see an increased demand for service by older clients whose communication difficulty is caused by a combination of hearing loss and cognitive impairment. For these individuals, early detection of mild cognitive impairment is critical for providing timely medical intervention and social support. METHOD: This tutorial provides information about cognition of older adults, mild cognitive impairment, and cognitive screening tests, with the purpose of assisting audiologists in identifying and appropriately referring potential cases of cognitive impairment. RESULTS: Topics addressed also include how to administer cognitive screening tests on individuals with hearing loss, how to use test results in audiology practice, and the potential of using cognitive screening tests for evaluating the benefit of clinical interventions. CONCLUSIONS: As health care professionals who serve the aging population, audiologists are likely to encounter cases of undiagnosed cognitive impairment. In order to provide timely referral for medical assistance as well as an optimized individual outcome of audiologic interventions, audiologists should be trained to recognize an abnormality in older clients' cognitive status.

Chosen Listening Levels for Music With and Without the Use of Hearing Aids.

PURPOSE: The objective of this study was to describe chosen listening levels (CLLs) for recorded music for listeners with hearing loss in aided and unaided conditions. METHOD: The study used a within-subject, repeated-measures design with 13 adult hearing-aid users. The music included rock and classical samples with different amounts of audio-industry compression limiting. CLL measurements were taken at ear level (i.e., at input to the hearing aid) and at the tympanic membrane. RESULTS: For aided listening, average CLLs were 69.3 dBA at the input to the hearing aid and 80.3 dBA at the tympanic membrane. For unaided listening, average CLLs were 76.9 dBA at the entrance to the ear canal and 77.1 dBA at the tympanic membrane. Although wide intersubject variability was observed, CLLs were not associated with audiometric thresholds. CLLs for rock music were higher than for classical music at the tympanic membrane, but no differences were observed between genres for ear-level CLLs. The amount of audio-industry compression had no significant effect on CLLs. CONCLUSION: By describing the levels of recorded music chosen by hearing-aid users, this study provides a basis for ecologically valid testing conditions in clinical and laboratory settings.

The Hearing-Aid Audio Quality Index (HAAQI).

This paper presents an index designed to predict music quality for individuals listening through hearing aids. The index is "intrusive", that is, it compares the degraded signal being evaluated to a reference signal. The index is based on a model of the auditory periphery that includes the effects of hearing loss. Outputs from the auditory model are used to measure changes in the signal time-frequency envelope modulation, temporal fine structure, and long-term spectrum caused by the hearing aid processing. The index is constructed by combining a term sensitive to noise and nonlinear distortion with a second term sensitive to changes in the long-term spectrum. The index is fitted to an existing database of music quality judgments made by listeners having normal or impaired hearing. The data comprise ratings for three music excerpts (classical orchestra, jazz trio, and jazz singer), each processed through 100 conditions representative of hearing-aid processing and listening situations. The overall accuracy of the index is high, with a correlation coefficient of 0.970 when computed over all of the processing conditions and averaged over the combined groups of listeners having normal and impaired hearing.

Comparing the information conveyed by envelope modulation for speech intelligibility, speech quality, and music quality.

This paper uses mutual information to quantify the relationship between envelope modulation fidelity and perceptual responses. Data from several previous experiments that measured speech intelligibility, speech quality, and music quality are evaluated for normal-hearing and hearing-impaired listeners. A model of the auditory periphery is used to generate envelope signals, and envelope modulation fidelity is calculated using the normalized cross-covariance of the degraded signal envelope with that of a reference signal. Two procedures are used to describe the envelope modulation: (1) modulation within each auditory frequency band and (2) spectro-temporal processing that analyzes the modulation of spectral ripple components fit to successive short-time spectra. The results indicate that low modulation rates provide the highest information for intelligibility, while high modulation rates provide the highest information for speech and music quality. The low-to-mid auditory frequencies are most important for intelligibility, while mid frequencies are most important for speech quality and high frequencies are most important for music quality. Differences between the spectral ripple components used for the spectro-temporal analysis were not significant in five of the six experimental conditions evaluated. The results indicate that different modulation-rate and auditory-frequency weights may be appropriate for indices designed to predict different types of perceptual relationships.

Derivations of the band-importance function: A cross-procedure comparison.

The purpose of this study was to compare band-importance functions (BIFs) derived by two different procedures. Intelligibility data from native speakers of Korean were used. BIFs were derived using an established procedure reported by Studebaker and Sherbecoe [J. Speech Lang. Hear. Res. 34, 427-438 (1991)] and by a recently published method reported by Kates [J. Acoust. Soc. Am. 134(5), EL459-EL464 (2013)]. The BIFs produced by the two different procedures were similar. These results indicate that the BIF calculation procedure by Kates is accurate for sentences as well as for the monosyllables used in its derivation.

Working memory and intelligibility of hearing-aid processed speech.

Previous work suggested that individuals with low working memory capacity may be at a disadvantage in adverse listening environments, including situations with background noise or substantial modification of the acoustic signal. This study explored the relationship between patient factors (including working memory capacity) and intelligibility and quality of modified speech for older individuals with sensorineural hearing loss. The modification was created using a combination of hearing aid processing [wide-dynamic range compression (WDRC) and frequency compression (FC)] applied to sentences in multitalker babble. The extent of signal modification was quantified via an envelope fidelity index. We also explored the contribution of components of working memory by including measures of processing speed and executive function. We hypothesized that listeners with low working memory capacity would perform more poorly than those with high working memory capacity across all situations, and would also be differentially affected by high amounts of signal modification. Results showed a significant effect of working memory capacity for speech intelligibility, and an interaction between working memory, amount of hearing loss and signal modification. Signal modification was the major predictor of quality ratings. These data add to the literature on hearing-aid processing and working memory by suggesting that the working memory-intelligibility effects may be related to aggregate signal fidelity, rather than to the specific signal manipulation. They also suggest that for individuals with low working memory capacity, sensorineural loss may be most appropriately addressed with WDRC and/or FC parameters that maintain the fidelity of the signal envelope.

Music preferences with hearing aids: effects of signal properties, compression settings, and listener characteristics.

OBJECTIVES: Current knowledge of how to design and fit hearing aids to optimize music listening is limited. Many hearing-aid users listen to recorded music, which often undergoes compression limiting (CL) in the music industry. Therefore, hearing-aid users may experience twofold effects of compression when listening to recorded music: music-industry CL and hearing-aid wide dynamic-range compression (WDRC). The goal of this study was to examine the roles of input-signal properties, hearing-aid processing, and individual variability in the perception of recorded music, with a focus on the effects of dynamic-range compression. DESIGN: A group of 18 experienced hearing-aid users made paired-comparison preference judgments for classical and rock music samples using simulated hearing aids. Music samples were either unprocessed before hearing-aid input or had different levels of music-industry CL. Hearing-aid conditions included linear gain and individually fitted WDRC. Combinations of four WDRC parameters were included: fast release time (50 msec), slow release time (1,000 msec), three channels, and 18 channels. Listeners also completed several psychophysical tasks. RESULTS: Acoustic analyses showed that CL and WDRC reduced temporal envelope contrasts, changed amplitude distributions across the acoustic spectrum, and smoothed the peaks of the modulation spectrum. Listener judgments revealed that fast WDRC was least preferred for both genres of music. For classical music, linear processing and slow WDRC were equally preferred, and the main effect of number of channels was not significant. For rock music, linear processing was preferred over slow WDRC, and three channels were preferred to 18 channels. Heavy CL was least preferred for classical music, but the amount of CL did not change the patterns of WDRC preferences for either genre. Auditory filter bandwidth as estimated from psychophysical tuning curves was associated with variability in listeners' preferences for classical music. CONCLUSIONS: Fast, multichannel WDRC often leads to poor music quality, whereas linear processing or slow WDRC are generally preferred. Furthermore, the effect of WDRC is more important for music preferences than music-industry CL applied to signals before the hearing-aid input stage. Variability in hearing-aid users' perceptions of music quality may be partially explained by frequency resolution abilities.

Dynamic range for speech materials in korean, english, and mandarin: a cross-language comparison.

PURPOSE: The purpose of this study was to identify whether differences in dynamic range (DR) are evident across the spoken languages of Korean, English, and Mandarin. METHOD: Recorded sentence-level speech materials were used as stimuli. DR was quantified using different definitions of DR (defined as the range in decibels from the highest to the lowest signal intensities), for several integration times (from 1 to 512 ms) and in different frequency bands (center frequencies [CFs] ranging from 150 to 8600 Hz). RESULTS: Across the 3 languages, DR was affected in similar ways with regard to changes in DR definition and integration time. In contrast, across-language differences in DR were evident when considering frequency-band effects. Specifically, the DR for Korean was smaller than the English DR and the Mandarin DR in low-frequency bands (less than the CF of 455 Hz). Compared with Korean and Mandarin, the DR for English was smallest in mid-frequency bands (between the CF of 455 Hz and 4050 Hz) and was greatest in high-frequency bands (above the CF of 4050 Hz). CONCLUSION: The observed differences in DR across languages suggest that the best-fit DR for Korean and Mandarin may be different than the best fit for English.

Effects of age on melody and timbre perception in simulations of electro-acoustic and cochlear-implant hearing.

OBJECTIVES: Recent evidence suggests that age might affect the ability of listeners to process fundamental frequency cues in speech, and that this difficulty might impact the ability of older listeners to use and combine envelope and fine structure cues available in simulations of electro-acoustic and cochlear-implant hearing. The purpose of this article is to examine whether this difficulty extends to music. Specially, this study focuses on whether older listeners have a decreased ability to use and combine different types of cues in the perception of melody and timbre. DESIGN: A group of older listeners with normal to near-normal hearing and a group of younger listeners with normal hearing participated in the melody and timbre recognition tasks of the University of Washington Clinical Assessment of Music Perception test. The recognition tasks were completed for five different processing conditions: (1) an unprocessed condition; (2) an eight-channel vocoding condition that simulated a traditional cochlear implant and contained temporal envelope cues; (3) a simulation of electro-acoustic stimulation (sEAS) that included a low-pass acoustic component and high-pass vocoded portion, and which provided fine structure and envelope cues; (4) a condition that included only the low-pass acoustic portion of the sEAS; and (5) a condition that included only the high-frequency vocoded portion of the sEAS stimulus. RESULTS: Melody recognition was excellent for both younger and older listeners in the conditions containing the unprocessed stimuli, the full sEAS stimuli, and the low-pass sEAS stimuli. Melody recognition was significantly worse in the cochlear-implant simulation condition, especially for the older group of listeners. Performance on the timbre task was highest for the unprocessed condition, and progressively decreased for the sEAS and cochlear-implant simulation conditions. Compared with younger listeners, older listeners had significantly poorer timbre recognition for all processing conditions. For melody recognition, the unprocessed low-frequency portion of the sEAS stimulus was the primary factor determining improved performance in the sEAS condition compared with the cochlear-implant simulation. For timbre recognition, both the unprocessed low-frequency and high-frequency vocoded portions of the sEAS stimulus contributed to sEAS improvement in the younger group. In contrast, most listeners in the older group were not able to take advantage of the high-frequency vocoded portion of the sEAS stimulus for timbre recognition. CONCLUSIONS: The results of this simulation study support the idea that older listeners will have diminished timbre and melody perception in traditional cochlear-implant listening due to degraded envelope processing. The findings also suggest that music perception by older listeners with cochlear implants will be improved with the addition of low-frequency residual hearing. However, these improvements might not be comparable for all dimensions of music perception. That is, more improvement might be evident for tasks that rely primarily on the low-frequency portion of the electro-acoustic stimulus (e.g., melody recognition), and less improvement might be evident in situations that require across-frequency integration of cues (e.g., timbre perception).