The Effects of Signal to Noise Ratio, T60 , Wide-Dynamic Range Compression Speed, and Digital Noise Reduction in a Virtual Restaurant Setting.

OBJECTIVES: Hearing aid processing in realistic listening environments is difficult to study effectively. Often the environment is unpredictable or unknown, such as in wearable aid trials with subjective report by the wearer. Some laboratory experiments create listening environments to exert tight experimental control, but those environments are often limited by physical space, a small number of sound sources, or room absorptive properties. Simulation techniques bridge this gap by providing greater experimental control over listening environments, effectively bringing aspects of the real-world into the laboratory. This project used simulation to study the effects of wide-dynamic range compression (WDRC) and digital noise reduction (DNR) on speech intelligibility in a reverberant environment with six spatialized competing talkers. The primary objective of this study was to determine the efficacy of WDRC and DNR in a complex listening environment using virtual auditory space techniques. DESIGN: Participants of greatest interest were listeners with hearing impairment. A group of listeners with clinically normal hearing was included to assess the effects of the simulation absent the complex effects of hearing loss. Virtual auditory space techniques were used to simulate a small restaurant listening environment with two different reverberation times (0.8 and 1.8 sec) in a range of signal to noise ratios (SNRs) (-8.5 to 11.5 dB SNR). Six spatialized competing talkers were included to further enhance realism. A hearing aid simulation was used to examine the degree to which speech intelligibility was affected by slow and fast WDRC in conjunction with the presence or absence of DNR. The WDRC and DNR settings were chosen to be reasonable estimates of hearing aids currently available to consumers. RESULTS: A WDRC × DNR × Hearing Status interaction was observed, such that DNR was beneficial for speech intelligibility when combined with fast WDRC speeds, but DNR was detrimental to speech intelligibility when WDRC speeds were slow. The pattern of the WDRC × DNR interaction was observed for both listener groups. Significant main effects of reverberation time and SNR were observed, indicating better performance with lower reverberation times and more positive SNR. CONCLUSIONS: DNR reduced low-amplitude noise before WDRC-amplified the low-intensity portions of the signal, negating one potential downside of fast WDRC and leading to an improvement in speech intelligibility in this simulation. These data suggest that, in some real-world environments that include both reverberation and noise, older listeners with hearing impairment may find speech to be more intelligible if DNR is activated when the hearing aid has fast compression time constants. Additional research is needed to determine the appropriate DNR strength and to confirm results in wearable hearing aids and a wider range of listening environments.

Effect of frequency compression on fricative perception between normal-hearing English and Mandarin listeners.

High-frequency speech information is susceptible to inaccurate perception in even mild to moderate forms of hearing loss. Some hearing aids employ frequency-lowering methods such as nonlinear frequency compression (NFC) to help hearing-impaired individuals access high-frequency speech information in more accessible lower-frequency regions. As such techniques cause significant spectral distortion, tests such as the S-Sh Confusion Test help optimize NFC settings to provide high-frequency audibility with the least distortion. Such tests have been traditionally based on speech contrasts pertinent to English. Here, the effects of NFC processing on fricative perception between English and Mandarin listeners are assessed. Small but significant differences in fricative discrimination were observed between the groups. The study demonstrates possible need for language-specific clinical fitting procedures for NFC.

The role of working memory in speech recognition by hearing-impaired older listeners: does the task matter?

OBJECTIVE: Working memory refers to a cognitive system that holds a limited amount of information in a temporarily heightened state of availability, for use in ongoing cognitive tasks. Research suggests a link between working memory and speech recognition. In this study, we investigated this relationship using two working memory tests that differed in regard to the operationalisation of the link between working memory and attention: the auditory visual divided attention test (AVDAT) and the widely used reading span test. DESIGN: The relationship between speech-in-noise recognition and working memory was examined for two different working memory tests that varied in methodological and theoretical aspects, using a within-subject design. STUDY SAMPLE: Nineteen hearing-impaired older listeners participated. RESULTS: We found a strong link between the reading span test and speech-in-noise recognition and a less robust link between the AVDAT and speech-in-noise recognition. There was evidence for the role of selective attention in speech-in-noise recognition, shown via the new AVDAT measure. CONCLUSION: Our findings suggest that the strength of the relationship between speech-in-noise recognition and working memory may be influenced by the match between the demands and the stimuli of the speech-in-noise task and those of the working memory test.

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.

Weaker older women gain more lower body strength than their stronger counterparts, but not muscle mass, following 12 weeks of resistance training.

We compared the magnitude of strength and muscle mass changes in response to resistance training (RT) between stronger older women and their weaker counterparts. Older women (n = 207) were grouped into tertiles according to their baseline muscular strength index. The upper and lower tertiles participants were categorized as stronger (STR, n = 69) and weaker (WKR, n = 69), respectively. Both groups engaged in a 12-week whole-body RT program. Outcomes included one-repetition maximum (1RM) tests in the three lifts and assessment of segmental lean soft tissue (LST) and skeletal muscle mass (SMM). The 1RM increase was similar between groups for the chest press [between-groups effect size of the differences (ESdiff) and 95% confidence interval (95%CI) = 0.10 (95%CI: -0.52, 0.31), P = 0.617] and preacher curl [ESdiff = 0.08 (95%CI: -0.48, 0.32), P = 0.681]. Changes were greater in WKR than STR for 1RM leg extension [ESdiff = -0.45 (95%CI: -0.86, -0.04), P = 0.030]. The increases of segmental LST and SMM were similar between-groups (ESdiff contains zero, P ≥ 0.434). We conclude that stronger and weaker older women benefit similarly for muscle mass and upper-limb strength gains. Notably, weaker older women may experience greater lower-limbs strength gains.

Does Varying Resistance Exercises for the Same Muscle Group Promote Greater Strength Gains?

ABSTRACT: Costa, BDV, Kassiano, W, Nunes, JP, Kunevaliki, G, Castro-E-Souza, P, Sugihara-Junior, P, Fernandes, RR, Cyrino, ES, and de Fortes, LS. Does varying resistance exercises for the same muscle group promote greater strength gains? J Strength Cond Res 36(11): 3032-3039, 2022-Two of the foremost principles of progression are progressive overload and variation. A way to vary within a resistance training (RT) program is to perform different exercises for the same muscle group; however, this strategy is still overlooked. The purpose of the present study was to compare strength adaptations between an RT routine that maintained the exercises fixed (N-VAR) and another that varied the exercises for the same muscle group during the weekly sessions (VAR). Twenty-three young men (23.3 ± 4.1 years) were randomly allocated to N-VAR ( n = 11) and VAR ( n = 12) conditions. The RT was performed 3 times a week for 9 weeks and consisted of a whole-body routine (3 sets of 8-12 repetitions). Maximum dynamic strength was assessed using the 1-repetition maximum test (1RM), and the isometric strength was assessed using an isokinetic dynamometer, before and after training. Following the training period, both groups increased the 1RM values in all exercises ( p ≤ 0.002), without significant differences between them ( p ≥ 0.20). In contrast, a greater increase ( p = 0.02) in isometric knee extension strength was showed to N-VAR (+12%) compared with VAR (+7%). There was no significant increase in both groups for isometric knee flexion strength (N-VAR, p = 0.10; VAR, p = 0.18). Our findings indicate that maintaining or varying the exercises for the same muscle group promotes similar adaptations in the maximum dynamic strength. In contrast, for the isometric strength in knee extension, maintaining the fixed exercises seems to be more interesting.

Effects of Directionality, Compression, and Working Memory on Speech Recognition.

OBJECTIVES: Previous research has shown that the association between hearing aid-processed speech recognition and individual working memory ability becomes stronger in more challenging conditions (e.g., higher background noise levels) and with stronger hearing aid processing (e.g., fast-acting wide dynamic range compression, WDRC). To date, studies have assumed omnidirectional microphone settings and collocated speech and noise conditions to study such relationships. Such conditions fail to recognize that most hearing aids are fit with directional processing that may improve the signal to noise ratio (SNR) and speech recognition in spatially separated speech and noise conditions. Here, we considered the possibility that directional processing may reduce the signal distortion arising from fast-acting WDRC and in turn influence the relationship between working memory ability and speech recognition with WDRC processing. The combined effects of hearing aid processing (WDRC and directionality) and SNR were quantified using a signal modification metric (cepstral correlation), which measures temporal envelope changes in the processed signal with respect to a linearly amplified reference. It was hypothesized that there will be a weaker association between working memory ability and speech recognition for hearing aid processing conditions that result in overall less signal modification (i.e., fewer changes to the processed envelope). DESIGN: Twenty-three individuals with bilateral, mild to moderately severe sensorineural hearing loss participated in the study. Participants were fit with a commercially available hearing aid, and signal processing was varied in two dimensions: (1) Directionality (omnidirectional [OMNI] versus fixed-directional [DIR]), and (2) WDRC speed (fast-acting [FAST] versus slow-acting [SLOW]). Sentence recognition in spatially separated multi-talker babble was measured across a range of SNRs: 0 dB, 5 dB, 10 dB, and quiet. Cumulative signal modification was measured with individualized hearing aid settings, for all experimental conditions. A linear mixed-effects model was used to determine the relationship between speech recognition, working memory ability, and cumulative signal modification. RESULTS: Signal modification results showed a complex relationship between directionality and WDRC speed, which varied by SNR. At 0 and 5 dB SNRs, signal modification was lower for SLOW than FAST regardless of directionality. However, at 10 dB SNR and in the DIR listening condition, there was no signal modification difference between FAST and SLOW. Consistent with previous studies, the association of speech recognition in noise with working memory ability depended on the level of signal modification. Contrary to the hypothesis above, however, there was a significant association of speech recognition with working memory only at lower levels of signal modification, and speech recognition increased at a faster rate for individuals with better working memory as signal modification decreased with DIR and SLOW. CONCLUSIONS: This research suggests that working memory ability remains a significant predictor of speech recognition when WDRC and directionality are applied. Our findings revealed that directional processing can reduce the detrimental effect of fast-acting WDRC on speech cues at higher SNRs, which affects speech recognition ability. Contrary to some previous research, this study showed that individuals with better working memory ability benefitted more from a decrease in signal modification than individuals with poorer working memory ability.

Does Performing Different Resistance Exercises for the Same Muscle Group Induce Non-homogeneous Hypertrophy?

The study aimed to compare the effect of performing the same or different exercises for a muscle group on resistance training (RT) sessions on muscle hypertrophy at different sites along muscle length. Twenty-two detrained men (23.3±4.1 years) were randomly allocated to the following groups: a group that performed the same exercises in all training sessions (N-VAR=11) or one that varied the exercises for the same muscle groups (VAR=11). All were submitted to 3 weekly sessions for nine weeks. Muscle thickness was assessed at the proximal, middle, and distal sites of the lateral and anterior thigh, elbow flexors, and extensors by B-mode ultrasound. The VAR group significantly increased all the sites analyzed (P<0.05). Furthermore, the proximal site of the lateral thigh showed a larger relative increase when compared to the middle site (P<0.05). In contrast, the N-VAR group were not revealed significant improvements only for the middle site of the lateral thigh and the proximal site of the elbow flexors (P>0.05). Our results suggest that to perform different resistance exercises can induce hypertrophy of all sites assessed in detrained young men.

Recognising foreign-accented speech of varying intelligibility and linguistic complexity: insights from older listeners with or without hearing loss.

OBJECTIVE: The goal of this study was to assess recognition of foreign-accented speech of varying intelligibility and linguistic complexity in older adults. It is important to understand the factors that influence the recognition of this commonly encountered type of speech, in a population that remains understudied in this regard. DESIGN: A repeated measures design was used. Listeners repeated back linguistically simple and complex sentences heard in noise. The sentences were produced by three talkers of varying intelligibility: one native American English, one foreign-accented talker of high intelligibility and one foreign-accented talker of low intelligibility. Percentage word recognition in sentences was measured. STUDY SAMPLE: Twenty-five older listeners with a range of hearing thresholds participated. RESULTS: We found a robust interaction between talker intelligibility and linguistic complexity. Recognition accuracy was higher for simple versus complex sentences, but only for the native and high intelligibility foreign-accented talkers. This pattern was present after effects of working memory capacity and hearing acuity were taken into consideration. CONCLUSION: Older listeners exhibit qualitatively different speech processing strategies for low versus high intelligibility foreign-accented talkers. Differences in recognition accuracy for words presented in simple versus in complex sentence contexts only emerged for speech over a threshold of intelligibility.

Switching Streams Across Ears to Evaluate Informational Masking of Speech-on-Speech.

OBJECTIVES: This study aimed to evaluate the informational component of speech-on-speech masking. Speech perception in the presence of a competing talker involves not only informational masking (IM) but also a number of masking processes involving interaction of masker and target energy in the auditory periphery. Such peripherally generated masking can be eliminated by presenting the target and masker in opposite ears (dichotically). However, this also reduces IM by providing listeners with lateralization cues that support spatial release from masking (SRM). In tonal sequences, IM can be isolated by rapidly switching the lateralization of dichotic target and masker streams across the ears, presumably producing ambiguous spatial percepts that interfere with SRM. However, it is not clear whether this technique works with speech materials. DESIGN: Speech reception thresholds (SRTs) were measured in 17 young normal-hearing adults for sentences produced by a female talker in the presence of a competing male talker under three different conditions: diotic (target and masker in both ears), dichotic, and dichotic but switching the target and masker streams across the ears. Because switching rate and signal coherence were expected to influence the amount of IM observed, these two factors varied across conditions. When switches occurred, they were either at word boundaries or periodically (every 116 msec) and either with or without a brief gap (84 msec) at every switch point. In addition, SRTs were measured in a quiet condition to rule out audibility as a limiting factor. RESULTS: SRTs were poorer for the four switching dichotic conditions than for the nonswitching dichotic condition, but better than for the diotic condition. Periodic switches without gaps resulted in the worst SRTs compared to the other switch conditions, thus maximizing IM. CONCLUSIONS: These findings suggest that periodically switching the target and masker streams across the ears (without gaps) was the most efficient in disrupting SRM. Thus, this approach can be used in experiments that seek a relatively pure measure of IM, and could be readily extended to translational research.

The Association Between Physiological Noise Levels and Speech Understanding in Noise.

OBJECTIVES: Traditionally, elevated hearing thresholds have been considered to be the main contributors to difficulty understanding speech in noise; yet, patients will often report difficulties with speech understanding in noise despite having audiometrically normal hearing. The purpose of this cross-sectional study was to critically evaluate the relationship of various metrics of auditory function (behavioral thresholds and otoacoustic emissions) on speech understanding in noise in a large sample of audiometrically normal-hearing individuals. DESIGN: Behavioral hearing thresholds, distortion product otoacoustic emission (DPOAE) levels, stimulus-frequency otoacoustic emission levels, and physiological noise (quantified using OAE noise floors) were measured from 921 individuals between 10 and 68 years of age with normal pure-tone averages. The quick speech-in-noise (QuickSIN) test outcome, quantified as the signal-to-noise ratio (SNR) loss, was used as the metric of speech understanding in noise. Principle component analysis (PCA) and linear regression modeling were used to evaluate the relationship between the measures of auditory function and speech in noise performance. RESULTS: Over 25% of participants exhibited mild or worse degree of SNR loss. PCA revealed DPOAE levels at 12.5 to 16 kHz to be significantly correlated with the variation in QuickSIN scores, although correlations were weak (R = 0.017). Out of all the metrics evaluated, higher levels of self-generated physiological noise accounted for the most variance in QuickSIN performance (R = 0.077). CONCLUSIONS: Higher levels of physiological noise were associated with worse QuickSIN performance in listeners with normal hearing sensitivity. We propose that elevated physiological noise levels in poorer speech in noise performers could diminish the effective SNR, thereby negatively impacting performance as seen by poorer QuickSIN scores.

Quantifying the Range of Signal Modification in Clinically Fit Hearing Aids.

OBJECTIVES: Hearing aids provide various signal processing techniques with a range of parameters to improve the listening experience for a hearing-impaired individual. In previous studies, we reported significant differences in signal modification for mild versus strong signal processing in commercially available hearing aids. In this study, the authors extend this work to clinically prescribed hearing aid fittings based on best-practice guidelines. The goals of this project are to determine the range of cumulative signal modification in clinically fit hearing aids across manufacturers and technology levels and the effects of listening conditions including signal to noise ratio (SNR) and presentation level on these signal modifications. DESIGN: We identified a subset of hearing aids that were representative of a typical clinical setting. Deidentified hearing aid fitting data were obtained from three audiology clinics for adult hearing aid users with sensorineural hearing loss for a range of hearing sensitivities. Matching laboratory hearing aids were programmed with the deidentified fitting data. Output from these hearing aids was recorded at four SNRs and three presentation levels. The resulting signal modification was quantified using the cepstral correlation component of the Hearing Aid Speech Quality Index which measures the speech envelope changes in the context of a model of the listener's hearing loss. These metric values represent the hearing aid processed signal as it is heard by the hearing aid user. Audiometric information was used to determine the nature of any possible association with the distribution of signal modification in these clinically fit hearing aids. RESULTS: In general, signal modification increased as SNR decreased and presentation level increased. Differences across manufacturers were significant such that the effect of presentation level varied differently at each SNR, for each manufacturer. This result suggests that there may be variations across manufacturers in processing various listening conditions. There was no significant effect of technology level. There was a small effect of pure-tone average on signal modification for one manufacturer, but no effect of audiogram slope. Finally, there was a broad range of measured signal modification for a given hearing loss, for the same manufacturer and listening condition. CONCLUSIONS: The signal modification values in this study are representative of commonly fit hearing aids in clinics today. The results of this study provide insights into how the range of signal modifications obtained in real clinical fittings compares with a previous study. Future studies will focus on the behavioral implications of signal modifications in clinically fit hearing aids.

Test Administration Methods and Cognitive Test Scores in Older Adults with Hearing Loss.

In light of the high prevalence of hearing loss and cognitive impairment in the aging population, it is important to know how cognitive tests should be administered for older adults with hearing loss. The purpose of the present study is to examine this question with a cognitive screening test and a working memory test. Specifically, we asked the following questions in 2 experiments. First, does a controlled amplification method affect cognitive test scores? Second, does test modality (visual vs. auditory) impact cognitive test scores? Three test administration conditions were created for both Montreal Cognitive Assessment (MoCA) and working memory test (a word recognition and recall test): auditory amplified, auditory unamplified, and visual. The auditory administration was implemented through a computer program to control for presentation level while the visual condition was implemented through timed computer slides. Data were collected from older individuals with mild-to-moderate sensorineural hearing loss. We did not find any effect of amplification or test modality on the total score of the cognitive screening test (i.e., MoCA). Amplification improved working memory performance as measured by word recall performance, but test modality (auditory vs. visual) did not. These results are consistent with literature in demonstrating a downstream effect of audibility on working memory performance. From a clinical perspective, these findings are informative for developing clinical administration protocols of these tests for older individuals with hearing loss.

Recognition of foreign-accented speech in noise: The interplay between talker intelligibility and linguistic structure.

Foreign-accented speech recognition is typically tested with linguistically simple materials, which offer a limited window into realistic speech processing. The present study examined the relationship between linguistic structure and talker intelligibility in several sentence-in-noise recognition experiments. Listeners transcribed simple/short and more complex/longer sentences embedded in noise. The sentences were spoken by three talkers of varying intelligibility: one native, one high-, and one low-intelligibility non-native English speakers. The effect of linguistic structure on sentence recognition accuracy was modulated by talker intelligibility. Accuracy was disadvantaged by increasing complexity only for the native and high intelligibility foreign-accented talkers, whereas no such effect was found for the low intelligibility foreign-accented talker. This pattern emerged across conditions: low and high signal-to-noise ratios, mixed and blocked stimulus presentation, and in the absence of a major cue to prosodic structure, the natural pitch contour of the sentences. Moreover, the pattern generalized to a different set of three talkers that matched the intelligibility of the original talkers. Taken together, the results in this study suggest that listeners employ qualitatively different speech processing strategies for low- versus high-intelligibility foreign-accented talkers, with sentence-related linguistic factors only emerging for speech over a threshold of intelligibility. Findings are discussed in the context of alternative accounts.

Sentence perception in noise by hearing-aid users predicted by syllable-constituent perception and the use of context.

Masked sentence perception by hearing-aid users is strongly correlated with three variables: (1) the ability to hear phonetic details as estimated by the identification of syllable constituents in quiet or in noise; (2) the ability to use situational context that is extrinsic to the speech signal; and (3) the ability to use inherent context provided by the speech signal itself. This approach is called "the syllable-constituent, contextual theory of speech perception" and is supported by the performance of 57 hearing-aid users in the identification of 109 syllable constituents presented in a background of 12-talker babble and the identification of words in naturally spoken sentences presented in the same babble. A simple mathematical model, inspired in large part by Boothroyd and Nittrouer [(1988). J. Acoust. Soc. Am. 84, 101-114] and Fletcher [Allen (1996) J. Acoust. Soc. Am. 99, 1825-1834], predicts sentence perception from listeners' abilities to recognize isolated syllable constituents and to benefit from context. When the identification accuracy of syllable constituents is greater than about 55%, individual differences in context utilization play a minor role in determining the sentence scores. As syllable-constituent scores fall below 55%, individual differences in context utilization play an increasingly greater role in determining sentence scores. Implications for hearing-aid design goals and fitting procedures are discussed.

Different Foot Positioning During Calf Training to Induce Portion-Specific Gastrocnemius Muscle Hypertrophy.

Nunes, JP, Costa, BDV, Kassiano, W, Kunevaliki, G, Castro-e-Souza, P, Rodacki, ALF, Fortes, LS, and Cyrino, ES. Different foot positioning during calf training to induce portion-specific gastrocnemius muscle hypertrophy. J Strength Cond Res 34(8): 2347-2351, 2020-The aim of this study was to compare the changes in gastrocnemius muscle thickness (MT) between conditions such as which foot was pointed outward (FPO), foot was pointed inward (FPI), or foot was pointed forward (FPF). Twenty-two young men (23 ± 4 years) were selected and performed a whole-body resistance training program 3 times per week for 9 weeks, with differences in the exercise specific for calves. The calf-raise exercise was performed unilaterally, in a pin-loaded seated horizontal leg-press machine, in 3 sets of 20-25 repetitions for training weeks 1-3 and 4 sets for weeks 4-9. Each subject's leg was randomly assigned for 1 of the 3 groups according to the foot position: FPO, FPI, and FPF. Measurements with a B-mode ultrasound were performed to assess changes in MT of medial and lateral gastrocnemius heads. After the training period, there were observed increases in MT of both medial (FPO = 8.4%, FPI = 3.8%, and FPF = 5.8%) and lateral (FPO = 5.5%, FPI = 9.1%, and FPF = 6.4%) gastrocnemius heads, and significant differences for magnitude of the gains were observed between FPO and FPI conditions (p < 0.05). Positioning FPO potentiated the increases in MT of the medial gastrocnemius head, whereas FPI provided greater gains for the lateral gastrocnemius head. Our results suggest that head-specific muscle hypertrophy may be obtained selectively for gastrocnemius after 9 weeks of calf training in young male adults.

Effects of Reverberation on the Relation Between Compression Speed and Working Memory for Speech-in-Noise Perception.

OBJECTIVES: Previous study has suggested that when listening in modulated noise, individuals benefit from different wide dynamic range compression (WDRC) speeds depending on their working memory ability. Reverberation reduces the modulation depth of signals and may impact the relation between WDRC speed and working memory. The purpose of this study was to examine this relation across a range of reverberant conditions. DESIGN: Twenty-eight older listeners with mild-to-moderate sensorineural hearing impairment were recruited in the present study. Individual working memory was measured using a Reading Span test. Sentences were combined with noise at two signal to noise ratios (2 and 5 dB SNR), and reverberation was simulated at a range of reverberation times (0.00, 0.75, 1.50, and 3.00 sec). Speech intelligibility was measured in listeners when listening to the sentences processed with simulated fast-acting and slow-acting WDRC conditions. RESULTS: There was a significant relation between WDRC speed and working memory with minimal or no reverberation. Consistent with previous research, this relation was such that individuals with high working memory had higher speech intelligibility with fast-acting WDRC, and individuals with low working memory performed better with slow-acting WDRC. However, at longer reverberation times, there was no relation between WDRC speed and working memory. CONCLUSIONS: Consistent with previous studies, results suggest that there is an advantage of tailoring WDRC speed based on an individual's working memory under anechoic conditions. However, the present results further suggest that there may not be such a benefit in reverberant listening environments due to reduction in signal modulation.

Understanding Variability in Individual Response to Hearing Aid Signal Processing in Wearable Hearing Aids.

OBJECTIVES: Previous work has suggested that individual characteristics, including amount of hearing loss, age, and working memory ability, may affect response to hearing aid signal processing. The present study aims to extend work using metrics to quantify cumulative signal modifications under simulated conditions to real hearing aids worn in everyday listening environments. Specifically, the goal was to determine whether individual factors such as working memory, age, and degree of hearing loss play a role in explaining how listeners respond to signal modifications caused by signal processing in real hearing aids, worn in the listener's everyday environment, over a period of time. DESIGN: Participants were older adults (age range 54-90 years) with symmetrical mild-to-moderate sensorineural hearing loss. We contrasted two distinct hearing aid fittings: one designated as mild signal processing and one as strong signal processing. Forty-nine older adults were enrolled in the study and 35 participants had valid outcome data for both hearing aid fittings. The difference between the two settings related to the wide dynamic range compression and frequency compression features. Order of fittings was randomly assigned for each participant. Each fitting was worn in the listener's everyday environments for approximately 5 weeks before outcome measurements. The trial was double blind, with neither the participant nor the tester aware of the specific fitting at the time of the outcome testing. Baseline measures included a full audiometric evaluation as well as working memory and spectral and temporal resolution. The outcome was aided speech recognition in noise. RESULTS: The two hearing aid fittings resulted in different amounts of signal modification, with significantly less modification for the mild signal processing fitting. The effect of signal processing on speech intelligibility depended on an individual's age, working memory capacity, and degree of hearing loss. Speech recognition with the strong signal processing decreased with increasing age. Working memory interacted with signal processing, with individuals with lower working memory demonstrating low speech intelligibility in noise with both processing conditions, and individuals with higher working memory demonstrating better speech intelligibility in noise with the mild signal processing fitting. Amount of hearing loss interacted with signal processing, but the effects were small. Individual spectral and temporal resolution did not contribute significantly to the variance in the speech intelligibility score. CONCLUSIONS: When the consequences of a specific set of hearing aid signal processing characteristics were quantified in terms of overall signal modification, there was a relationship between participant characteristics and recognition of speech at different levels of signal modification. Because the hearing aid fittings used were constrained to specific fitting parameters that represent the extremes of the signal modification that might occur in clinical fittings, future work should focus on similar relationships with more diverse types of signal processing parameters.

The ability to glimpse dynamic pitch in noise by younger and older listeners.

While dynamic pitch is helpful for speech perception in temporally-modulated noise, the ability to benefit from this cue varies substantially among older listeners. To examine the perceptual factors that contribute to this variability, this study aimed to characterize individuals' ability to perceive dynamic pitch in temporally-modulated noise using dynamic pitch segments extracted from real speech and embedded in temporally modulated noise. Data from younger and older listeners showed stronger pitch contours were more easily perceived than weaker pitch contours. The metric significantly predicted speech-in-noise ability in older listeners. Potential implications of this work are discussed.

The use of self-report measures to examine changes in perception in response to fittings using different signal processing parameters.

Clinicians have long used self-report methods to assess hearing aid benefit. However, there are fewer data as to whether self-report instruments can be used to compare differences between signal processing settings. This study examined how self-perceived performance varied as a function of modifications in signal processing using two self-report measures. Data were collected as part of a double-blind randomised crossover clinical trial. Participants were fit with two fittings: mild processing (slow time constants, disabled frequency lowering) and strong processing (fast time constants, frequency lowering enabled). The speech, spatial, and qualities of hearing (SSQ) questionnaire and the Effectiveness of Auditory Rehabilitation (EAR) questionnaire were collected at multiple time points. Older adults with sensorineural hearing loss who had not used hearing aids within the previous year participated (49 older adults were consented; 40 were included in the final data analyses). Findings show that listeners report a difference in perceived performance when hearing aid features are modified. Both self-report measures were able to capture this change in perceived performance. Self-report measures provide a tool for capturing changes in perceived performance when hearing aid processing features are modified and may enhance provision of an evidence-based hearing aid fitting.