Effects of age and hearing loss on the intelligibility of interrupted speech

Interrupted mosaic speech revisited: Gain and loss in intelligibility by stretchinga)

Our previous investigation on the effect of stretching spectrotemporally degraded and temporally interrupted speech stimuli showed remarkable intelligibility gains [Udea, Takeichi, and Wakamiya (2022). J. Acoust. Soc. Am. 152(2), 970-980]. In this previous study, however, gap durations and temporal resolution were confounded. In the current investigation, we therefore observed the intelligibility of so-called mosaic speech while dissociating the effects of interruption and temporal resolution. The intelligibility of mosaic speech (20 frequency bands and 20 ms segment duration) declined from 95% to 78% and 33% by interrupting it with 20 and 80 ms gaps. Intelligibility improved, however, to 92% and 54% (14% and 21% gains for 20 and 80 ms gaps, respectively) by stretching mosaic segments to fill silent gaps (n = 21). By contrast, the intelligibility was impoverished to a minimum of 9% (7% loss) when stretching stimuli interrupted with 160 ms gaps. Explanations based on auditory grouping, modulation unmasking, or phonemic restoration may account for the intelligibility improvement by stretching, but not for the loss. The probability summation model accounted for "U"-shaped intelligibility curves and the gain and loss of intelligibility, suggesting that perceptual unit length and speech rate may affect the intelligibility of spectrotemporally degraded speech stimuli.

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.

Cognitive and linguistic abilities and perceptual restoration of missing speech: Evidence from online assessment

When speech is clear, speech understanding is a relatively simple and automatic process. However, when the acoustic signal is degraded, top-down cognitive and linguistic abilities, such as working memory capacity, lexical knowledge (i.e., vocabulary), inhibitory control, and processing speed can often support speech understanding. This study examined whether listeners aged 22-63 (mean age 42 years) with better cognitive and linguistic abilities would be better able to perceptually restore missing speech information than those with poorer scores. Additionally, the role of context and everyday speech was investigated using high-context, low-context, and realistic speech corpi to explore these effects. Sixty-three adult participants with self-reported normal hearing completed a short cognitive and linguistic battery before listening to sentences interrupted by silent gaps or noise bursts. Results indicated that working memory was the most reliable predictor of perceptual restoration ability, followed by lexical knowledge, and inhibitory control and processing speed. Generally, silent gap conditions were related to and predicted by a broader range of cognitive abilities, whereas noise burst conditions were related to working memory capacity and inhibitory control. These findings suggest that higher-order cognitive and linguistic abilities facilitate the top-down restoration of missing speech information and contribute to individual variability in perceptual restoration.

Recognition of Interrupted Speech, Text, and Text-Supplemented Speech by Older Adults: Effect of Interruption Rate

PURPOSE

Studies of speech and text interruption indicate that the interruption rate influences the perceptual information available, from whole words at slow rates to subphonemic cues at faster interruptions rates. In young adults, the benefit obtained from text supplementation of speech may depend on the type of perceptual information available in either modality. Age commonly reduces temporal aspects of information processing, which may influence the benefit older adults obtain from text-supplemented speech across interruption rates.

METHOD

Older adults were tested unimodally and multimodally with spoken and printed sentences that were interrupted by silence or white space at various rates.

RESULTS

Results demonstrate U-shaped performance-rate functions for all modality conditions, with minimal performance around interruption rates of 2-4 Hz. Comparison to previous studies with younger adults indicates overall poorer recognition for interrupted materials by the older adults. However, as a group, older adults can integrate information between the two modalities to a similar degree as younger adults. Individual differences in multimodal integration were noted.

CONCLUSION

Overall, these results indicate that older adults, while demonstrating poorer overall performance in comparison to younger adults, successfully combine distributed partial information across speech and text modalities to facilitate sentence recognition.

Older adult recognition error patterns when listening to interrupted speech and speech in steady-state noise

This study examined sentence recognition errors made by older adults in degraded listening conditions compared to a previous sample of younger adults. We examined speech recognition errors made by older normal-hearing adults who repeated sentences that were corrupted by steady-state noise (SSN) or periodically interrupted by noise to preserve 33%, 50%, or 66% of the sentence. Responses were transcribed and coded for the number and type of keyword errors. Errors increased with decreasing preservation of the sentence. Similar sentence recognition was observed between SSN and the greatest amount of interruption (33%). Errors were predominately at the word level rather than at the phoneme level and consisted of omission or substitution of keywords. Compared to younger listeners, older listeners made more total errors and omitted more whole words when speech was highly degraded. They also made more whole word substitutions when speech was more preserved. In addition, the semantic relatedness of the substitution errors to the sentence context varied according to the distortion condition, with greater context effects in SSN than interruption. Overall, older listeners made errors reflecting poorer speech representations. Error analyses provide a more detailed account of speech recognition by identifying changes in the type of errors made across listening conditions and listener groups.

Auditory closure with visual cues: Relationship with working memory and semantic memory

The role of working memory (WM) and long-term lexical-semantic memory (LTM) in the perception of interrupted speech with and without visual cues, was studied in 29 native English speakers. Perceptual stimuli were periodically interrupted sentences filled with speech noise. The memory measures included an LTM semantic fluency task, verbal WM, and visuo-spatial WM tasks. Whereas perceptual performance in the audio-only condition demonstrated a significant positive association with listeners' semantic fluency, perception in audio-video mode did not. These results imply that when listening to distorted speech without visual cues, listeners rely on lexical-semantic retrieval from LTM to restore missing speech information.

Speech recognition scores in bilateral and unilateral atretic ears

OBJECTIVE

Congenital aural atresia causes severe conductive hearing loss disturbing auditory development. The differences in speech recognition were investigated between bilateral and unilateral aural atresia.

DESIGN

The maximum speech recognition scores (SRSs) were compared between patients with bilateral and unilateral aural atresia. In patients with unilateral aural atresia, the maximum SRSs were compared between the atretic and unaffected ears. Furthermore, the correct response rates for test material monosyllables were compared with those of patients with sensorineural hearing loss (SNHL), which had been previously obtained.

STUDY SAMPLE

Twenty-four patients with aural atresia (8 bilateral, and 16 unilateral) participated.

RESULTS

The maximum SRS in unilateral atretic ears (median: 72%) was significantly lower than that in unaffected ears (median: 89%) (p < 0.05) and in bilateral atretic ears (median: 91%) (p < 0.05). Patients with aural atresia had relatively high correct response rates for monosyllables with low correct response rates by patients with SNHL. Conversely, incorrect responses were obtained for several words for which high correct-response rates were attained by patients with SNHL.

CONCLUSIONS

Poor unilateral atretic-ear development may induce low speech recognition, and the mechanisms underlying speech-recognition reduction differ from those in SNHL.

Modulation rate and age effect on intermittent speech recognition

ABSTRACT Purpose: to investigate the auditory recognition of intermittent speech in relation to different modulation rates and ages. Methods: 20 young people, 20 middle-aged adults, and 16 older adults, all of them with auditory thresholds equal to or lower than 25 dB HL up to the frequency of 4000 Hz. The participants were submitted to intermittent speech recognition tests presented in three modulation conditions: 4 Hz, 10 Hz, and 64 Hz. The percentages of correct answers were compared between age groups and modulation rates. ANOVA and post hoc tests were conducted to investigate the modulation rate effect, and the mixed linear regression model (p < 0.001). Results: regarding the age effect, the data showed a significant difference between young people and older adults, and between middle-aged and older adults. As for the modulation rate effect, the indexes of correct answers were significantly lower at the slower rate (4 Hz) in the three age groups. Conclusion: an age effect was verified on intermittent speech recognition: older adults have greater difficulty. A modulation rate effect was also noticed in the three age groups: the higher the rate, the better the performance.

Perceptual Organization of Interrupted Speech and Text

PURPOSE

Visual recognition of interrupted text may predict speech intelligibility under adverse listening conditions. This study investigated the nature of the linguistic information and perceptual processes underlying this relationship.

METHOD

To directly compare the perceptual organization of interrupted speech and text, we examined the recognition of spoken and printed sentences interrupted at different rates in 14 adults with normal hearing. The interruption method approximated deletion and retention of rate-specific linguistic information (0.5-64 Hz) in speech by substituting either white space or silent intervals for text or speech in the original sentences.

RESULTS

A similar U-shaped pattern of cross-rate variation in performance was observed in both modalities, with minima at 2 Hz. However, at the highest and lowest interruption rates, recognition accuracy was greater for text than speech, whereas the reverse was observed at middle rates. An analysis of word duration and the frequency of word sampling across interruption rates suggested that the location of the function minima was influenced by perceptual reconstruction of whole words. Overall, the findings indicate a high degree of similarity in the perceptual organization of interrupted speech and text.

CONCLUSION

The observed rate-specific variation in the perception of speech and text may potentially affect the degree to which recognition accuracy in one modality is predictive of the other.

Age effects on perceptual organization of speech: Contributions of glimpsing, phonemic restoration, and speech segregation

In realistic listening environments, speech perception requires grouping together audible fragments of speech, filling in missing information, and segregating the glimpsed target from the background. The purpose of this study was to determine the extent to which age-related difficulties with these tasks can be explained by declines in glimpsing, phonemic restoration, and/or speech segregation. Younger and older adults with normal hearing listened to sentences interrupted with silence or envelope-modulated noise, presented either in quiet or with a competing talker. Older adults were poorer than younger adults at recognizing keywords based on short glimpses but benefited more when envelope-modulated noise filled silent intervals. Recognition declined with a competing talker but this effect did not interact with age. Results of cognitive tasks indicated that faster processing speed and better visual-linguistic closure were predictive of better speech understanding. Taken together, these results suggest that age-related declines in speech recognition may be partially explained by difficulty grouping short glimpses of speech into a coherent message.

Age effects on perceptual organization of speech: Contributions of glimpsing, phonemic restoration, and speech segregation

In realistic listening environments, speech perception requires grouping together audible fragments of speech, filling in missing information, and segregating the glimpsed target from the background. The purpose of this study was to determine the extent to which age-related difficulties with these tasks can be explained by declines in glimpsing, phonemic restoration, and/or speech segregation. Younger and older adults with normal hearing listened to sentences interrupted with silence or envelope-modulated noise, presented either in quiet or with a competing talker. Older adults were poorer than younger adults at recognizing keywords based on short glimpses but benefited more when envelope-modulated noise filled silent intervals. Recognition declined with a competing talker but this effect did not interact with age. Results of cognitive tasks indicated that faster processing speed and better visual-linguistic closure were predictive of better speech understanding. Taken together, these results suggest that age-related declines in speech recognition may be partially explained by difficulty grouping short glimpses of speech into a coherent message.

How repetition influences speech understanding by younger, middle-aged and older adults

OBJECTIVE

To examine benefit from immediate repetition of a masked speech message in younger, middle-aged and older adults.

DESIGN

Participants listened to sentences in conditions where only the target message was repeated, and when both the target message and its accompanying masker (noise or speech) were repeated. In a follow-up experiment, the effect of repetition was evaluated using a square-wave modulated noise masker to compare benefit when listeners were exposed to the same glimpses of the target message during first and second presentation versus when the glimpses differed.

STUDY SAMPLE

Younger, middle-aged and older adults (n = 16/group) for the main experiment; 15 younger adults for the follow-up experiment.

RESULTS

Repetition benefit was larger when the target but not the masker was repeated for all groups. This was especially true for older adults, suggesting that these individuals may be more negatively affected when a background message is repeated. Data obtained using noise maskers suggest that it is slightly more beneficial when listeners hear different (versus identical) portions of speech between initial presentation and repetition.

CONCLUSIONS

Although subtle age-related differences were found in some conditions, results confirm that repetition is an effective repair strategy for listeners spanning the adult age range.

Role of working memory and lexical knowledge in perceptual restoration of interrupted speech

The role of working memory (WM) capacity and lexical knowledge in perceptual restoration (PR) of missing speech was investigated using the interrupted speech perception paradigm. Speech identification ability, which indexed PR, was measured using low-context sentences periodically interrupted at 1.5 Hz. PR was measured for silent gated, low-frequency speech noise filled, and low-frequency fine-structure and envelope filled interrupted conditions. WM capacity was measured using verbal and visuospatial span tasks. Lexical knowledge was assessed using both receptive vocabulary and meaning from context tests. Results showed that PR was better for speech noise filled condition than other conditions tested. Both receptive vocabulary and verbal WM capacity explained unique variance in PR for the speech noise filled condition, but were unrelated to performance in the silent gated condition. It was only receptive vocabulary that uniquely predicted PR for fine-structure and envelope filled conditions. These findings suggest that the contribution of lexical knowledge and verbal WM during PR depends crucially on the information content that replaced the silent intervals. When perceptual continuity was partially restored by filler speech noise, both lexical knowledge and verbal WM capacity facilitated PR. Importantly, for fine-structure and envelope filled interrupted conditions, lexical knowledge was crucial for PR.

Auditory Verbal Working Memory as a Predictor of Speech Perception in Modulated Maskers in Listeners With Normal Hearing

PURPOSE

Background noise can interfere with our ability to understand speech. Working memory capacity (WMC) has been shown to contribute to the perception of speech in modulated noise maskers. WMC has been assessed with a variety of auditory and visual tests, often pertaining to different components of working memory. This study assessed the relationship between speech perception in modulated maskers and components of auditory verbal working memory (AVWM) over a range of signal-to-noise ratios.

METHOD

Speech perception in noise and AVWM were measured in 30 listeners (age range 31-67 years) with normal hearing. AVWM was estimated using forward digit recall, backward digit recall, and nonword repetition.

RESULTS

After controlling for the effects of age and average pure-tone hearing threshold, speech perception in modulated maskers was related to individual differences in the phonological component of working memory (as assessed by nonword repetition) but only in the least favorable signal-to-noise ratio. The executive component of working memory (as assessed by backward digit) was not predictive of speech perception in any conditions.

CONCLUSIONS

AVWM is predictive of the ability to benefit from temporal dips in modulated maskers: Listeners with greater phonological WMC are better able to correctly identify sentences in modulated noise backgrounds.

Aging and Spectro-Temporal Integration of Speech

The purpose of this study was to determine the effects of age on the spectro-temporal integration of speech. The hypothesis was that the integration of speech fragments distributed over frequency, time, and ear of presentation is reduced in older listeners-even for those with good audiometric hearing. Younger, middle-aged, and older listeners (10 per group) with good audiometric hearing participated. They were each tested under seven conditions that encompassed combinations of spectral, temporal, and binaural integration. Sentences were filtered into two bands centered at 500 Hz and 2500 Hz, with criterion bandwidth tailored for each participant. In some conditions, the speech bands were individually square wave interrupted at a rate of 10 Hz. Configurations of uninterrupted, synchronously interrupted, and asynchronously interrupted frequency bands were constructed that constituted speech fragments distributed across frequency, time, and ear of presentation. The over-arching finding was that, for most configurations, performance was not differentially affected by listener age. Although speech intelligibility varied across condition, there was no evidence of performance deficits in older listeners in any condition. This study indicates that age, per se, does not necessarily undermine the ability to integrate fragments of speech dispersed across frequency and time.

Glimpsing Speech in the Presence of Nonsimultaneous Amplitude Modulations From a Competing Talker: Effect of Modulation Rate, Age, and Hearing Loss

PURPOSE

This study investigated how listeners process acoustic cues preserved during sentences interrupted by nonsimultaneous noise that was amplitude modulated by a competing talker.

METHOD

Younger adults with normal hearing and older adults with normal or impaired hearing listened to sentences with consonants or vowels replaced with noise amplitude modulated by a competing talker. Sentences were spectrally shaped according to individual audiograms or to the mean audiogram from the listeners with hearing impairment for a younger spectrally shaped control group. The modulation spectrum of the noise was low-pass filtered at different modulation cutoff frequencies. The effect of noise level was also examined.

RESULTS

Performance declined when nonsimultaneous masker modulation included faster rates and was maximized when masker modulation matched the preserved primary speech modulation. Vowels resulted in better performance compared with consonants at slower modulation cutoff rates, likely due to suprasegmental features. Poorer overall performance was observed with increased age or hearing loss, and for listeners who received spectrally shaped speech.

CONCLUSIONS

Nonsimultaneous amplitude modulations from a competing talker significantly interacted with the preserved speech segment, and additional listener factors were observed for age and hearing loss. Importantly, listeners may obtain benefit from nonsimultaneous competing modulations when they match the preserved modulations of the sentence.

Modulation masking and glimpsing of natural and vocoded speech during single-talker modulated noise: Effect of the modulation spectrum

Compared to notionally steady-state noise, modulated maskers provide a perceptual benefit for speech recognition, in part due to preserved speech information during the amplitude dips of the masker. However, overlap in the modulation spectrum between the target speech and the competing modulated masker may potentially result in modulation masking, and thereby offset the release from energetic masking. The current study investigated masking release provided by single-talker modulated noise. The overlap in the modulation spectra of the target speech and the modulated noise masker was varied through time compression or expansion of the competing masker. Younger normal hearing adults listened to sentences that were unprocessed or noise vocoded to primarily limit speech recognition to the preserved temporal envelope cues. For unprocessed speech, results demonstrated improved performance with masker modulation spectrum shifted up or down compared to the target modulation spectrum, except for the most extreme time expansion. For vocoded speech, significant masking release was observed with the slowest masker rate. Perceptual results combined with acoustic analyses of the preserved glimpses of the target speech suggest contributions of modulation masking and cognitive-linguistic processing as factors contributing to performance.

Modulation masking and glimpsing of natural and vocoded speech during single-talker modulated noise: Effect of the modulation spectrum

Compared to notionally steady-state noise, modulated maskers provide a perceptual benefit for speech recognition, in part due to preserved speech information during the amplitude dips of the masker. However, overlap in the modulation spectrum between the target speech and the competing modulated masker may potentially result in modulation masking, and thereby offset the release from energetic masking. The current study investigated masking release provided by single-talker modulated noise. The overlap in the modulation spectra of the target speech and the modulated noise masker was varied through time compression or expansion of the competing masker. Younger normal hearing adults listened to sentences that were unprocessed or noise vocoded to primarily limit speech recognition to the preserved temporal envelope cues. For unprocessed speech, results demonstrated improved performance with masker modulation spectrum shifted up or down compared to the target modulation spectrum, except for the most extreme time expansion. For vocoded speech, significant masking release was observed with the slowest masker rate. Perceptual results combined with acoustic analyses of the preserved glimpses of the target speech suggest contributions of modulation masking and cognitive-linguistic processing as factors contributing to performance.

The intelligibility of interrupted and temporally altered speech: Effects of context, age, and hearing loss

Temporal constraints on the perception of interrupted speech were investigated by comparing the intelligibility of speech that was periodically gated (PG) and subsequently either temporally compressed (PGTC) by concatenating remaining speech fragments or temporally expanded (PGTE) by doubling the silent intervals between speech fragments. Experiment 1 examined the effects of PGTC and PGTE at different gating rates (0.5 -16 Hz) on the intelligibility of words and sentences for young normal-hearing adults. In experiment 2, older normal-hearing (ONH) and older hearing-impaired (OHI) adults were tested with sentences only. The results of experiment 1 indicated that sentences were more intelligible than words. In both experiments, PGTC sentences were less intelligible than either PG or PGTE sentences. Compared with PG sentences, the intelligibility of PGTE sentences was significantly reduced by the same amount for ONH and OHI groups. Temporal alterations tended to produce a U-shaped rate-intelligibility function with a dip at 2-4 Hz, indicating that temporal alterations interacted with the duration of speech fragments. The present findings demonstrate that both aging and hearing loss negatively affect the overall intelligibility of interrupted and temporally altered speech. However, a mild-to-moderate hearing loss did not exacerbate the negative effects of temporal alterations associated with aging.