Binaural Temporal Fine Structure Research Articles

The relationship between interaural delay in binaural gap detection and sensitivity to temporal fine structure in young adults with or without musical training experience.

Humans can detect the presence of a break in interaural correlation (BIC, also called binaural gap) even if a large interaural time delay (ITD) is introduced, which is important for detecting, recognizing, and localizing sounds in everyday environments. To investigate the relationship between interaural delay in binaural gap detection and the sensitivity of temporal fine structure (TFS), 40 young college students with normal hearing took the BIC delay threshold test, the TFS1 test (the test of monaural TFS sensitivity), and the TFS-AF test (the test of binaural TFS sensitivity). All participants were asked whether they had any musical training experience in their childhood. Results showed that the BIC delay threshold was significantly correlated with the TFS1 test (r =−0.426, p = 0.006), but not with the TFS-AF performance (r =−0.005, p = 0.997). The correlation between BIC delay threshold and monaural TFS sensitivity was observed in the non-music training group (r =−0.508, p = 0.010), but not in the music training group (r =−0.290, p = 0.295). These findings suggest that the interaural delay in binaural gap detection is related to the monaural sensitivity of TFS, this significant correlation was mainly found in young adults without musical training experience.

Speech in Noise: Implications of Age, Hearing Loss, and Cognition

Introduction: Individuals with hearing loss have reduced hearing sensitivity and may not adequately process the temporal cues in acoustic signals. Cognitive skills that decrease with aging and hearing loss contribute negatively on the ability to understand speech. Hence, they may experience communication problems in noisy environments. The aim of the study was to investigate the effect of sloping high-frequency hearing loss on speech perception in noise and to examine the impact of temporal and cognitive processing in young and middle-age adults. Methods: Speech in noise (SIN), temporal processing, and cognitive tests were conducted to hearing loss and normal hearing individuals aged 18–59 years. The measurements included the matrix sentence test, binaural temporal fine structure sensitivity (TFS) test, Visual Aural Digit Span (VADS), and Auditory Verbal Learning Test (AVLT). Twenty participants with normal hearing were recruited in the control group, whereas 20 participants with hearing loss at high frequencies were composed of the study group. Results: Hierarchical regression analysis for SIN was performed by entering 3 separate blocks of independent variables. We entered age and hearing loss into the first block, which explained a significant amount of variability in SIN (R2 = 0.72, p < 0.001). Block 2 was comprised of scores from TFS sensitivity test, and this independent variable characterized temporal processing (R2 change = 0.002, p < 0.001). Block 3 was consisted of scores from VADS test and AVLT; these variables characterized cognitive processing and accounted for a good portion of SIN variance (R2 change = 0.04, p < 0.001). The age, hearing loss, and VADS contributed independently in the presence of all independent variables. Conclusion: The final model accounted for 76.2% of the variance in SIN. The results suggested that sloping hearing loss, aging, and cognitive decline affected auditory performance, and the poor performance starts from an early age. Additionally, the findings indicated that a more comprehensive approach might be recommended to evaluate the listening skills and identify communication problems.

Development of binaural temporal fine structure sensitivity in children.

The highest frequency for which the temporal fine structure (TFS) of a sinewave can be compared across ears varies between listeners with an upper limit of about 1400 Hz for young normal-hearing adults (YNHA). In this study, binaural TFS sensitivity was investigated for 63 typically developing children, aged 5 years, 6 months to 9 years, 4 months using the temporal fine structure-adaptive frequency (TFS-AF) test of Füllgrabe, Harland, Sęk, and Moore [Int. J. Audiol. 56, 926-935 (2017)]. The test assesses the highest frequency at which an interaural phase difference (IPD) of ϕ° can be distinguished from an IPD of 0°. The values of ϕ were 30° and 180°. The starting frequency was 200 Hz. The thresholds for the children were significantly lower (worse) than the thresholds reported by Füllgrabe, Harland, Sęk, and Moore [Int. J. Audiol. 56, 926-935 (2017)] for YNHA. For both values of ϕ, the median age at which children performed above chance level was significantly higher (p < 0.001) than for those who performed at chance. For the subgroup of 40 children who performed above chance for ϕ = 180°, the linear regression analyses showed that the thresholds for ϕ = 180° increased (improved) significantly with increasing age (p < 0.001) with adult-like thresholds predicted to be reached at 10 years, 2 months of age. The implications for spatial release from masking are discussed.

Effects of rehabilitation training on an elderly population with mild to moderate hearing loss: study protocol for a randomised clinical trial

Background: Age-related hearing loss (presbycusis) is a form of hearing loss in over 60-years-olds and has a negative impact on quality of life. Presbycusis is multifactorial and is predominately characterised with a loss of speech perception in noise. In the cochlea, auditory filters decompose broadband sound into a series of narrowband output signals, which contains two kinds of temporal information: slow changes in overall amplitude envelope (ENV) and faster variations in temporal fine structure (TFS). TFS is important for recognition of target speech in noise. The main aim of the study is to evaluate the effect of TFS rehabilitation training in participants over the age of 60 years with mild to moderate hearing loss. Methods: A randomised clinical trial conducted on 30 participants with mild (loss of 20-39dB HL) to moderate (40-69dB HL) hearing loss, aged between 60 and 75 years old. Participants with conductive hearing loss, abnormal middle ear pathology and central nervous system disease were excluded. Participants were selected randomly to an intervention and control group with a 1:1 ratio. Rehabilitation for the intervention Group are 30-minute sessions three times a week for a total five weeks of vowel consonant vowel words that are used to eliminate ENV and keep only TFS. Word in noise test, binaural TFS test, and Speech, Spatial and Qualities of Hearing Scale scores are performed at the beginning and end of study to evaluate the effect of rehabilitation training. Conclusion: Life expectancy in the elderly has improved, leading to an increased prevalence of age-related diseases including presbycusis. A literature review highlighted that TFS damage is permanent; however, in this study we will attempt to prove that TFS training may lead to speech in noise perception improvement. Trial registration: Registry of Clinical Trials, IRCT2019625044006N1 (7 th August 2019).

Binaural sensitivity and release from speech-on-speech masking in listeners with and without hearing loss.

Listeners with sensorineural hearing loss routinely experience less spatial release from masking (SRM) in speech mixtures than listeners with normal hearing. Hearing-impaired listeners have also been shown to have degraded temporal fine structure (TFS) sensitivity, a consequence of which is degraded access to interaural time differences (ITDs) contained in the TFS. Since these "binaural TFS" cues are critical for spatial hearing, it has been hypothesized that degraded binaural TFS sensitivity accounts for the limited SRM experienced by hearing-impaired listeners. In this study, speech stimuli were noise-vocoded using carriers that were systematically decorrelated across the left and right ears, thus simulating degraded binaural TFS sensitivity. Both (1) ITD sensitivity in quiet and (2) SRM in speech mixtures spatialized using ITDs (or binaural release from masking; BRM) were measured as a function of TFS interaural decorrelation in young normal-hearing and hearing-impaired listeners. This allowed for the examination of the relationship between ITD sensitivity and BRM over a wide range of ITD thresholds. This paper found that, for a given ITD sensitivity, hearing-impaired listeners experienced less BRM than normal-hearing listeners, suggesting that binaural TFS sensitivity can account for only a modest portion of the BRM deficit in hearing-impaired listeners. However, substantial individual variability was observed.

Consequences of interaural decorrelation of speech temporal fine structure

The ability to understand a target speech signal against a background of interfering speech signals is typically improved when the interfering signals are spatially separated (spatial release from masking; SRM). Swaminathan et al. (2016) found a significant reduction in SRM when the temporal fine structure (TFS) across the left and right ears was decorrelated, suggesting that binaural TFS provides important cues that support SRM. One interpretation is that degrading binaural TFS prevents the extraction of reliable interaural time differences (ITDs), which in turn leads to a reduction in SRM. We tested this hypothesis by systematically decorrelating the binaural TFS, and measuring the effects on both ITD discrimination for speech stimuli and SRM in normal hearing listeners. We show that decorrelation leads to a systematic increase in ITD discrimination thresholds, as well as a systematic decrease in SRM. This supports the idea that binaural TFS is needed to access ITD information in speech, which is in turn required for SRM. Additionally, the relationship between these two tasks provides a framework for determining the extent to which reduced SRM in listeners with hearing loss can be attributed to reduced sensitivity to binaural TFS.

Binaural sensitivity to temporal fine structure and lateralization ability in children with suspected (central) auditory processing disorder

ObjectivePrevious studies have shown that a subgroup of children with suspected (central) auditory processing disorder (SusCAPD) have insufficient ability to use binaural cues to benefit from spatial processing. Thus, they experience considerable listening difficulties in challenging auditory environments, such as classrooms. Some researchers have also indicated the probable role of binaural temporal fine structure (TFS) in the perceptual segregation of target signal from noise and hence in speech perception in noise. Therefore, in the present study, in order to further investigate the underlying reason for listening problems against background noise in this group of children, their performance was measured using binaural TFS sensitivity test (TFS-LF) as well as behavioral auditory lateralization in noise test, both of which are based on binaural temporal cues processing. MethodsParticipants in this analytical study included 91 children with normal hearing and no listening problems and 41 children (9–12 years old) with SusCAPD who found it challenging to understand speech in noise. Initially, the ability to use binaural TFS was measured at three frequencies (250, 500 and 750Hz) in both the groups, and the results of preliminary evaluations were compared between normal children and those with SusCAPD who participated in the study. Thereafter, the binaural performance of the 16 children with SusCAPD who had higher thresholds than the normal group at all three frequencies tested in TFS-LF test was examined using the lateralization test in 7 spatial locations. ResultsTotal 16 of the 41 children with SusCAPD who participated in this study (39%) showed poor performance on the TFS-LF test at all three frequencies, compared to both normal children and other children in the APD group (p<0.05). Furthermore, children in the APD group with binaural TFS coding deficits at all three frequencies revealed significant differences in the lateralization test results compared to normal children (p<0.05). ConclusionFindings of the current study demonstrated that one of the underlying causes for the difficulty understanding speech in noisy environments experienced by a subgroup of children with SusCAPD can be the reduced ability to benefit from binaural TFS information. This study also showed that a reduced ability to use binaural TFS cues in the group of children with SusCAPD was accompanied by reduced binaural processing abilities in the lateralization test which also admit the presence of binaural temporal processing deficits in this group of children.

Cortical Correlates of Binaural Temporal Processing Deficits in Older Adults.

This study was designed to evaluate binaural temporal processing in young and older adults using a binaural masking level difference (BMLD) paradigm. Using behavioral and electrophysiological measures within the same listeners, a series of stimulus manipulations was used to evaluate the relative contribution of binaural temporal fine-structure and temporal envelope cues. We evaluated the hypotheses that age-related declines in the BMLD task would be more strongly associated with temporal fine-structure than envelope cues and that age-related declines in behavioral measures would be correlated with cortical auditory evoked potential (CAEP) measures. Thirty adults participated in the study, including 10 young normal-hearing, 10 older normal-hearing, and 10 older hearing-impaired adults with bilaterally symmetric, mild-to-moderate sensorineural hearing loss. Behavioral and CAEP thresholds were measured for diotic (So) and dichotic (Sπ) tonal signals presented in continuous diotic (No) narrowband noise (50-Hz wide) maskers. Temporal envelope cues were manipulated by using two different narrowband maskers; Gaussian noise (GN) with robust envelope fluctuations and low-noise noise (LNN) with minimal envelope fluctuations. The potential to use temporal fine-structure cues was controlled by varying the signal frequency (500 or 4000 Hz), thereby relying on the natural decline in phase-locking with increasing frequency. Behavioral and CAEP thresholds were similar across groups for diotic conditions, while the masking release in dichotic conditions was larger for younger than for older participants. Across all participants, BMLDs were larger for GN than LNN and for 500-Hz than for 4000-Hz conditions, where envelope and fine-structure cues were most salient, respectively. Specific age-related differences were demonstrated for 500-Hz dichotic conditions in GN and LNN, reflecting reduced binaural temporal fine-structure coding. No significant age effects were observed for 4000-Hz dichotic conditions, consistent with similar use of binaural temporal envelope cues across age in these conditions. For all groups, thresholds and derived BMLD values obtained using the behavioral and CAEP methods were strongly correlated, supporting the notion that CAEP measures may be useful as an objective index of age-related changes in binaural temporal processing. These results demonstrate an age-related decline in the processing of binaural temporal fine-structure cues with preserved temporal envelope coding that was similar with and without mild-to-moderate peripheral hearing loss. Such age-related changes can be reliably indexed by both behavioral and CAEP measures in young and older adults.

A two-path model of auditory modulation detection using temporal fine structure and envelope cues.

A model using temporal-envelope cues was previously developed to explain perceptual interference effects between amplitude modulation and frequency modulation (FM). As that model could not accurately predict FM sensitivity and the interference effects, temporal fine structure (TFS) cues were added to the model. Thus, following the initial stage of the model consisting of a linear filter bank simulating cochlear filtering, processing was split into an 'envelope path' based on envelope power cues and a 'TFS path' based on a measure of the distribution of time intervals between successive zero-crossings. This yielded independent detectability indices for envelope and TFS cues, which were optimally combined to produce a single decision statistic. Independent internal noises in the envelope and TFS paths were adjusted to match the data. Simulations indicate that TFS cues are required to account for FM data for young normal-hearing listeners and that TFS processing is impaired for both older normal-hearing and hearing-impaired listeners. The role of TFS was further assessed by relating the monaural FM sensitivity to measures of interaural phase difference, commonly assumed to rely on binaural TFS sensitivity. The model demonstrates that binaural TFS sensitivity is considerably lower than monaural TFS sensitivity. Similar to FM thresholds, interaural phase difference sensitivity declined with age and hearing loss, although higher degradations were observed in binaural temporal processing compared to monaural processing. Overall, this model provides a novel tool to explore the mechanisms involved in FM processing in the normal auditory system and the degradations in FM sensitivity with ageing and hearing loss.

Senescent Changes in Sensitivity to Binaural Temporal Fine Structure.

Differences in the temporal fine structure (TFS) of sounds at the two ears are used for sound localization and for the perceptual analysis of complex auditory scenes. The ability to process this binaural TFS information is poorer for older than for younger participants, and this may contribute to age-related declines in the ability to understand speech in noisy situations. However, it is unclear how sensitivity to binaural TFS changes across the older age range. This article presents data for a test of binaural sensitivity to TFS, the “TFS-adaptive frequency” (AF) test, for 118 listeners aged 60 to 96 years with normal or near-normal low-frequency hearing, but a variety of patterns of hearing loss at higher frequencies. TFS-AF scores were significantly lower (i.e., poorer) than those for young adults. On average, scores decreased by about 162 Hz for each 10-year increase in age over the range 60 to 85 years. Individual variability increased with increasing age. Scores also declined as low-frequency audiometric thresholds worsened. The results illustrate the range of scores that can be obtained as a function of age and may be useful for the diagnosis and management of age-related hearing difficulties.

The Association Between the Processing of Binaural Temporal-Fine-Structure Information and Audiometric Threshold and Age: A Meta-Analysis.

The ability to process binaural temporal fine structure (TFS) information, which influences the perception of speech in spatially distributed soundscapes, declines with increasing hearing loss and age. Because of the relatively small sample sizes used in previous studies, and the population-unrepresentative distribution of hearing loss and ages within study samples, it has been difficult to determine the relative and combined contributions of hearing loss and age. The aim of this study was to survey published and unpublished studies that assessed binaural TFS sensitivity using the TFS-low frequency (LF) test. Results from 19 studies were collated, yielding sample sizes of 147 to 648, depending on the test frequency. At least for the test frequency of 500 Hz, there were at least 67 listeners in each of four adult age groups and the distribution of audiometric thresholds at the test frequency within each group was similar to that for the population as a whole. Binaural TFS sensitivity declined with increasing age across the adult lifespan and with increasing hearing loss in old adulthood. For all test frequencies, both audiometric threshold and age were significantly negatively correlated with TFS-LF sensitivity (r ranging from −0.19 to −0.64) but the correlation was always significantly higher for age than for audiometric threshold. Regression analyses showed that the standardized regression coefficient was greater for age than for audiometric threshold, and that there was a significant interaction; the effect of increasing age among older listeners was greater when the hearing loss was ≥30 dB than when it was < 30 dB.

Evaluation of a Method for Determining Binaural Sensitivity to Temporal Fine Structure (TFS-AF Test) for Older Listeners With Normal and Impaired Low-Frequency Hearing.

The ability to process binaural temporal fine structure (TFS) information was assessed using the TFS-AF test (where AF stands for adaptive frequency) for 26 listeners aged 60 years or more with normal or elevated low-frequency audiometric thresholds. The test estimates the highest frequency at which a fixed interaural phase difference (IPD) of ϕ (varied here between 30° and 180°) can be discriminated from an IPD of 0°, with higher thresholds indicating better performance. A sensation level of 30 dB was used. All listeners were able to perform the task reliably, giving thresholds well above the lowest allowed frequency of 30 Hz. The duration of a run averaged 5 min. Repeated testing of the normal-hearing listeners showed no significant practice effects. Thresholds varied markedly across listeners, but their ranking was fairly consistent across values of ϕ. Thresholds decreased (worsened) with decreasing ϕ and were lower than for a group of young listeners tested in an earlier study. There were weak to moderate, negative correlations between TFS-AF thresholds and audiometric thresholds at low frequencies (125–1000 Hz) but not at high frequencies (4000–8000 Hz). In conclusion, the TFS-AF test yielded a graded measure of binaural TFS sensitivity for all listeners. This contrasts with the TFS-LF (low-frequency) test, which measures the smallest detectable shift in IPD for a fixed frequency. The absence of practice effects and a reasonably short administration time make the TFS-AF test a good candidate for the assessment of sensitivity to changes in binaural TFS for older listeners without or with hearing loss.

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.

Role of Binaural Temporal Fine Structure and Envelope Cues in Cocktail-Party Listening.

While conversing in a crowded social setting, a listener is often required to follow a target speech signal amid multiple competing speech signals (the so-called "cocktail party" problem). In such situations, separation of the target speech signal in azimuth from the interfering masker signals can lead to an improvement in target intelligibility, an effect known as spatial release from masking (SRM). This study assessed the contributions of two stimulus properties that vary with separation of sound sources, binaural envelope (ENV) and temporal fine structure (TFS), to SRM in normal-hearing (NH) human listeners. Target speech was presented from the front and speech maskers were either colocated with or symmetrically separated from the target in azimuth. The target and maskers were presented either as natural speech or as "noise-vocoded" speech in which the intelligibility was conveyed only by the speech ENVs from several frequency bands; the speech TFS within each band was replaced with noise carriers. The experiments were designed to preserve the spatial cues in the speech ENVs while retaining/eliminating them from the TFS. This was achieved by using the same/different noise carriers in the two ears. A phenomenological auditory-nerve model was used to verify that the interaural correlations in TFS differed across conditions, whereas the ENVs retained a high degree of correlation, as intended. Overall, the results from this study revealed that binaural TFS cues, especially for frequency regions below 1500 Hz, are critical for achieving SRM in NH listeners. Potential implications for studying SRM in hearing-impaired listeners are discussed. Acoustic signals received by the auditory system pass first through an array of physiologically based band-pass filters. Conceptually, at the output of each filter, there are two principal forms of temporal information: slowly varying fluctuations in the envelope (ENV) and rapidly varying fluctuations in the temporal fine structure (TFS). The importance of these two types of information in everyday listening (e.g., conversing in a noisy social situation; the "cocktail-party" problem) has not been established. This study assessed the contributions of binaural ENV and TFS cues for understanding speech in multiple-talker situations. Results suggest that, whereas the ENV cues are important for speech intelligibility, binaural TFS cues are critical for perceptually segregating the different talkers and thus for solving the cocktail party problem.

The perception of apparent auditory source width in hearing-impaired adults

In a previous study [Whitmer, Seeber and Akeroyd, J. Acoust. Soc. Am. 132, 369-379 (2012)], it was demonstrated that older hearing-impaired (HI) listeners produced visual sketches of headphone-presented noises that were insensitive to changes in interaural coherence. The current study further explores this insensitivity by comparing (a) binaural temporal fine-structure (TFS) resolution and (b) sound localization precision to (c) auditory source width judgments. Thirty-five participants aged 26-81 years with normal to moderately impaired hearing (a) discriminated interaurally phase-shifted tones from diotic tones presented over headphones, (b) located 500-ms speech-spectrum filtered click trains presented over loudspeakers between ±30° in quiet, and (c) sketched the perceived width of low-pass, high-pass, and speech-spectrum noise stimuli presented over loudspeakers from 0° and simultaneously from ±45° at attenuations of 0-20 dB to generate partially coherent stimuli. The results showed a decreasing sensitivity to width with age and impairment which was related to binaural TFS threshold: the worse one's threshold-which was correlated with age-the less the perceived width increased with decreasing interaural coherence. These results suggest that senescent changes to the auditory system do not necessarily lead to perceptions of broader, more diffuse sound images based on interaural coherence.

Degraded temporal processing after traumatic brain injury

Hearing complaints are common following traumatic brain injury (TBI) even in the absence of peripheral auditory impairment. Study goals were to explore the mechanisms which underlie this complaint. Adult listeners with a history of mild TBI or concussion were compared to young and age-matched controls. All listeners had normal or near-normal audiometric thresholds. Listeners with TBI reported difficulty understanding speech in noise. We hypothesized that hearing complaints after TBI are related to damage to neural pathways resulting in degraded temporal resolution. A battery of psychophysical tasks were used to test this hypothesis, specifically: monaural temporal fine structure, to evaluate temporal coding of unresolved harmonics; binaural temporal fine structure, to evaluate temporal coding of a low-frequency sinusoid; interaural coherence, to evaluate sensitivity to the similarity of a correlated broadband noise; and masking level difference, to evaluate the ability to take advantage of interaural phase for tone detection in noise. Results showed individual differences in temporal processing ability among listeners with a history of TBI. Test scores varied from normal to significantly impaired, despite normal audiometry. These results suggest that auditory temporal processing may be related to difficulty understanding speech in noise after TBI. [Work supported by NIH.]

Binaural temporal fine structure sensitivity, cognitive function, and spatial speech recognition of hearing-impaired listeners (L)

The relationships between spatial speech recognition (SSR; the ability to understand speech in complex spatial environments), binaural temporal fine structure (TFS) sensitivity, and three cognitive tasks were assessed for 17 hearing-impaired listeners. Correlations were observed between SSR, TFS sensitivity, and two of the three cognitive tasks, which became non-significant when age effects were controlled for, suggesting that reduced TFS sensitivity and certain cognitive deficits may share a common age-related cause. The third cognitive measure was also significantly correlated with SSR, but not with TFS sensitivity or age, suggesting an independent non-age-related cause.

Can basic auditory and cognitive measures predict hearing-impaired listeners’ localization and spatial speech recognition abilities?

This study aimed to clarify the basic auditory and cognitive processes that affect listeners' performance on two spatial listening tasks: sound localization and speech recognition in spatially complex, multi-talker situations. Twenty-three elderly listeners with mild-to-moderate sensorineural hearing impairments were tested on the two spatial listening tasks, a measure of monaural spectral ripple discrimination, a measure of binaural temporal fine structure (TFS) sensitivity, and two (visual) cognitive measures indexing working memory and attention. All auditory test stimuli were spectrally shaped to restore (partial) audibility for each listener on each listening task. Eight younger normal-hearing listeners served as a control group. Data analyses revealed that the chosen auditory and cognitive measures could predict neither sound localization accuracy nor speech recognition when the target and maskers were separated along the front-back dimension. When the competing talkers were separated along the left-right dimension, however, speech recognition performance was significantly correlated with the attentional measure. Furthermore, supplementary analyses indicated additional effects of binaural TFS sensitivity and average low-frequency hearing thresholds. Altogether, these results are in support of the notion that both bottom-up and top-down deficits are responsible for the impaired functioning of elderly hearing-impaired listeners in cocktail party-like situations.