Simultaneous and forward masking of vowels and stop consonants: Effects of age, hearing loss, and spectral shaping

Effects of age on brainstem coding of speech glimpses in interrupted noise

Difficulty understanding speech in fluctuating backgrounds is common among older adults. Whereas younger adults are adept at interpreting speech based on brief moments when the signal-to-noise ratio is favorable, older adults use these glimpses of speech less effectively. Age-related declines in auditory brainstem function may degrade the fidelity of speech cues in fluctuating noise for older adults, such that brief glimpses of speech interrupted by noise segments are not faithfully represented in the neural code that reaches the cortex. This hypothesis was tested using electrophysiological recordings of the envelope following response (EFR) elicited by glimpses of speech-like stimuli varying in duration (42, 70, 210 ms) and interrupted by silence or intervening noise. Responses from adults aged 23-73 years indicated that both age and hearing sensitivity were associated with EFR temporal coherence and response magnitude. Age was better than hearing sensitivity for predicting temporal coherence, whereas hearing sensitivity was better than age for predicting response magnitude. Poorer-fidelity EFRs were observed with shorter glimpses and with the addition of intervening noise. However, losses of fidelity with glimpse duration and noise were not associated with participant age or hearing sensitivity. These results suggest that the EFR is sensitive to factors commonly associated with glimpsing but do not entirely account for age-related changes in speech recognition in fluctuating backgrounds.

Can Closed-Set Word Recognition Differentially Assess Vowel and Consonant Perception for School-Age Children With and Without Hearing Loss?

PURPOSE

Vowels and consonants play different roles in language acquisition and speech recognition, yet standard clinical tests do not assess vowel and consonant perception separately. As a result, opportunities for targeted intervention may be lost. This study evaluated closed-set word recognition tests designed to rely predominantly on either vowel or consonant perception and compared results with sentence recognition scores.

METHOD

Participants were children (5-17 years of age) and adults (18-38 years of age) with normal hearing and children with sensorineural hearing loss (7-17 years of age). Speech reception thresholds (SRTs) were measured in speech-shaped noise. Children with hearing loss were tested with their hearing aids. Word recognition was evaluated using a three-alternative forced-choice procedure, with a picture-pointing response; monosyllabic target words varied with respect to either consonant or vowel content. Sentence recognition was evaluated for low- and high-probability sentences. In a subset of conditions, stimuli were low-pass filtered to simulate a steeply sloping hearing loss in participants with normal hearing.

RESULTS

Children's SRTs improved with increasing age for words and sentences. Low-pass filtering had a larger effect for consonant-variable words than vowel-variable words for both children and adults with normal hearing, consistent with the greater high-frequency content of consonants. Children with hearing loss tested with hearing aids tended to perform more poorly than age-matched children with normal hearing, particularly for sentence recognition, but consonant- and vowel-variable word recognition did not appear to be differentially affected by the amount of high- and low-frequency hearing loss.

CONCLUSIONS

Closed-set recognition of consonant- and vowel-variable words appeared to differentially evaluate vowel and consonant perception but did not vary by configuration of hearing loss in this group of pediatric hearing aid users. Word scores obtained in this manner do not fully characterize the auditory abilities necessary for open-set sentence recognition, but they do provide a general estimate.

The effect of aging on identification of Mandarin consonants in normal and whisper registers

Consonant perception in older adults has been widely explored in recent years. However, how aging affects the identification of Mandarin consonants, especially in whispered condition, are under studied. Mandarin consonants and whispering speech have unique features, which may result in different identification difficulties for older adults. The current study investigated older adults' identification of Mandarin consonants in phonated and whispered conditions in comparison with the performance of younger adults. It was found that in phonated condition, older adults showed the lowest accuracy for affricatives and fricatives owing to their insensitivity to high-frequency information. The lower accuracy of affricatives and plosives was largely attributed to the difficulty in recognizing articulatory places. Identifying aspirated plosives was much more difficult than unaspirated counterparts for older adults. In whispered condition, the recognition of voiced consonants and aspirated-unaspirated distinction became challenging, especially for older adults. Contrary to the expectation, some consonants became easier to be recognized in the whispered condition, i.e., /p^h, tɕ^h, x/. These findings enrich our understanding of how aging affects consonant identification in different languages and less ideal conditions. It also suggests that the listener's ability, language uniqueness, and characteristics of distorted speech should be all taken into consideration when investigating speech perception in adverse conditions.

Effect of Age on Informational Masking: Differential Effects of Phonetic and Semantic Information in the Masker

PURPOSE

Speech recognition in noise is a ubiquitous problem in older listeners. Speech, the most commonly encountered noise in the real world, causes greater masking than noise maskers, a phenomenon called informational masking (IM). This is due to the lexical-semantic and/or acoustic-phonetic information present in speech maskers. In this study, we aimed to observe the age-related differences in speech recognition and the magnitudes of IM when the maskers varied in the type of linguistic information.

METHOD

In 30 young and 30 older individuals, we measured the signal-to-noise ratio required to obtain 50% correct identification under four-talker babble (lexical-semantic and acoustic-phonetic information), four-talker reverse babble (predominantly acoustic-phonetic information), and speech-shaped noise (SSN; energetic).

RESULTS

In both groups, the four-talker babble caused the greatest masking effect (worst performances), whereas the SSN resulted in the least masking effect (best performances). The effectiveness of IM due to the lexical-semantic information was comparable between the two groups. However, the effectiveness of IM due to the acoustic-phonetic information was significantly higher in the older listeners, causing worse performances.

CONCLUSIONS

The greater effectiveness of IM due to the acoustic-phonetic information (worse performance) could be due to the minimal-to-mild high-frequency hearing loss and the consequent temporal processing deficits observed in the older listeners. However, it is possible that the older listeners can employ compensatory mechanisms (such as life experiences, contextual cues, employing higher listening efforts, among many possible other mechanisms) to overcome some of these deficits.

SUPPLEMENTAL MATERIAL

https://doi.org/10.23641/asha.20405730.

Phonological and semantic similarity of misperceived words in babble: Effects of sentence context, age, and hearing loss

This study investigated how age and hearing loss influence the misperceptions made when listening to sentences in babble. Open-set responses to final words in sentences with low and high context were analyzed for younger adults with normal hearing and older adults with normal or impaired hearing. All groups performed similarly in overall accuracy but differed in error type. Misperceptions for all groups were analyzed according to phonological and semantic properties. Comparisons between groups indicated that misperceptions for older adults were more influenced by phonological factors. Furthermore, older adults with hearing loss omitted more responses. Overall, across all groups, results suggest that phonological confusions most explain misperceptions in low context sentences. In high context sentences, the meaningful sentence context appears to provide predictive cues that reduce misperceptions. When misperceptions do occur, responses tend to have greater semantic similarity and lesser phonological similarity to the target, compared to low context sentences. In this way, semantic similarity may index a postdictive process by which ambiguities due to phonological confusions are resolved to conform to the semantic context of the sentence. These patterns demonstrate that context, age, and hearing loss affect the misperceptions, and potential sentence interpretation, made when listening to sentences in babble.

Word Identification With Temporally Interleaved Competing Sounds by Younger and Older Adult Listeners

OBJECTIVES

The purpose of this experiment was to contribute to our understanding of the nature of age-related changes in competing speech perception using a temporally interleaved task.

DESIGN

Younger and older adults (n = 16/group) participated in this study. The target was a five-word sentence. The masker was one of the following: another five-word sentence; five brief samples of modulated noise; or five brief samples of environmental sounds. The stimuli were presented in a temporally interleaved manner, where the target and masker alternated in time, always beginning with the target. Word order was manipulated in the target (and in the masker during trials with interleaved words) to compare performance when the five words in each stream did versus did not create a syntactically correct sentence. Talker voice consistency also was examined by contrasting performance when each word in the target was spoken by the same talker or by different talkers; a similar manipulation was used for the masker when it consisted of words. Participants were instructed to repeat back the target words and ignore the intervening words or sounds. Participants also completed a subset of tests from the NIH Cognitive Toolbox.

RESULTS

Performance on this interleaved task was significantly associated with listener age and with a metric of cognitive flexibility, but it was not related to the degree of high-frequency hearing loss. Younger adults' performance on this task was better than that of older adults, especially for words located toward the end of the sentence. Both groups of participants were able to take advantage of correct word order in the target, and both were negatively affected, to a modest extent, when the masker words were in correct syntactic order. The two groups did not differ in how phonetic similarity between target and masker words influenced performance, and interleaved environmental sounds or noise had only a minimal effect for all listeners. The most robust difference between listener groups was found for the use of voice consistency: older adults, as compared with younger adults, were less able to take advantage of a consistent target talker within a trial.

CONCLUSIONS

Younger adults outperformed older adults when masker words were interleaved with target words. Results suggest that this difference was unlikely to be related to energetic masking and/or peripheral hearing loss. Rather, age-related changes in cognitive flexibility and problems encoding voice information appeared to underlie group differences. These results support the contention that, in real-life competing speech situations that produce both energetic and informational masking, older adults' problems are due to both peripheral and nonperipheral changes.

Speech aging: Production and perception

In this overview we describe literature on how speech production and speech perception change in healthy or normal aging across the adult lifespan. In the production section we review acoustic characteristics that have been investigated as potentially distinguishing younger and older adults. In the speech perception section studies concerning speaker age estimation and those investigating older listeners' perception are addressed. Our discussion focuses on major themes and other fruitful areas for future research. This article is categorized under: Linguistics > Language in Mind and Brain Linguistics > Linguistic Theory Psychology > Development and Aging.

The Extended Speech Transmission Index: Predicting speech intelligibility in fluctuating noise and reverberant rooms

The Speech Transmission Index (STI) is used to predict speech intelligibility in noise and reverberant environments. However, measurements and predictions in fluctuating noises lead to inaccuracies. In the current paper, the Extended Speech Transmission Index (ESTI) is presented in order to deal with these shortcomings. Speech intelligibility in normally hearing subjects was measured using stationary and fluctuating maskers. These results served to optimize model parameters. Data from the literature were then used to verify the ESTI-model. Model outcomes were accurate for stationary maskers, maskers with artificial fluctuations, and maskers with real life non-speech modulations. Maskers with speech-like characteristics introduced systematic errors in the model outcomes, probably due to a combination of modulation masking, context effects, and informational masking.

Age effects on the contributions of envelope and periodicity cues to recognition of interrupted speech in quiet and with a competing talker

Envelope and periodicity cues may provide redundant, additive, or synergistic benefits to speech recognition. The contributions of these cues may change under different listening conditions and may differ for younger and older adults. To address these questions, younger and older adults with normal hearing listened to interrupted sentences containing different combinations of envelope and periodicity cues in quiet and with a competing talker. Envelope and periodicity cues improved speech recognition for both groups, and their benefits were additive when both cues were available. Envelope cues were particularly important for older adults and for sentences with a competing talker.

Forward Masking of the Speech-Evoked Auditory Brainstem Response

HYPOTHESIS

The hypothesis tested was that forward masking of the speech-evoked auditory brainstem response (sABR) increases peak latency as an inverse function of masker-signal interval (Δt), and that the overall persistence of forward masking is age dependent.

BACKGROUND

Older listeners exhibit deficits in forward masking. If forward-masked sABRs provide an objective measure of the susceptibility of speech sounds to prior stimulation, then this provides a novel approach to examining the age dependence of temporal processing.

METHODS

A /da/ stimulus forward masked by speech-shaped noise (Δt = 4-64 ms) was used to measure sABRs in 10 younger and nine older participants. Forward masking of subsegments of the /da/ stimulus (Δt = 16 ms) and click trains (Δt = 0-64 ms) was also measured.

RESULTS

Forward-masked sABRs from young participants showed an increase in latency with decreasing Δt for the initial peak. Latency shifts for later peaks were smaller and more uniform. None of the peak latencies returned to baseline by Δt = 64 ms. Forward-masked /da/ subsegments showed peak latency shifts that did not depend simply on peak position, while forward-masked click trains showed latency shifts that were dependent on click position. The sABRs from older adults were less robust but confirmed the viability of the approach.

CONCLUSION

Forward masking of the sABR provides an objective measure of the susceptibility of the auditory system to prior stimulation. Failure of recovery functions to return to baseline suggests an interaction between forward masking by the prior masker and temporal effects within the stimulus itself.