Effects of age, speech rate, and type of test on temporal auditory processing

The effect of rhythm on selective listening in multiple-source environments for young and older adults

Understanding continuous speech with competing background sounds is challenging, particularly for older adults. One stimulus property that may aid listeners understanding of to-be-attended (target) material is temporal regularity (rhythm). In the context of speech-in-noise understanding, McAuley and colleagues recently showed a target rhythm effect whereby recognition of target speech was better when natural speech rhythm of a target talker was intact than when it was temporally altered. The current study replicates the target rhythm effect using a synthetic vowel sequence paradigm in young adults (Experiment 1) and then uses this paradigm to investigate potential age-related changes in the effect of rhythm on recognition (Experiment 2). Listeners identified the last three vowels of temporally regular (isochronous) and irregular (anisochronous) synthetic vowel sequences in quiet and with a competing background sequence of vowel-like harmonic tone complexes presented at various tempos. The results replicated the target rhythm effect whereby temporal regularity in the vowel sequences improved identification accuracy of young listeners compared to irregular vowel sequences. The magnitude of the effect was not found to be influenced by background tempo, but faster background tempos led to greater vowel identification accuracy independent of regularity. Older listeners also demonstrated a target rhythm effect but received less benefit from the temporal regularity of the target sequences than did young listeners. This study highlights the importance of rhythm for understanding age-related differences in selective listening in complex environments and provides a novel paradigm for investigating effects of rhythm on perception.

The effect of video playback speed on learning and mind-wandering in younger and older adults

Prior work has demonstrated that watching videos at faster speeds does not significantly impair learning in younger adults; however, it was previously unclear how increased video speed impacts memory in older adults. Additionally, we investigated the effects of increased video speed on mind-wandering. We presented younger and older adults with a pre-recorded video lecture and manipulated the video to play at different speeds. After watching the video, participants predicted their performance on a memory test covering the material from the video and then completed said memory test. We demonstrated that although younger adults can watch lecture videos at faster speeds without significant deficits in memory, older adults' test performance is generally impaired when watching at faster speeds. Additionally, faster playback speeds seem to reduce mind-wandering (and mind-wandering was generally reduced in older adults relative to younger adults), potentially contributing to younger adults' preserved memory at faster speeds. Thus, while younger adults can watch videos at faster speeds without significant consequences, we advise against older adults watching at faster speeds.

Bluetooth Coupling in Hearing Aids: Effect on Audiovisual Speech Recognition and Quality Rating of Compressed Speech in Older Individuals with Sloping Hearing Loss

Introduction  Older individuals often report that they find it difficulty in enjoying watching television since they find it hard to follow the rapid intensity variations, and voice changes from scene to scene. Objective  The present study investigated the effect of coupling the hearing aid with the television via Bluetooth on audiovisual speech recognition and quality rating of compressed speech in older individuals with hearing loss. Method  Twenty participants in the age range of 60 to 75 years who had moderate to moderately severe sloping sensorineural hearing loss were bilaterally fitted with digital receiver in the canal hearing aids. The hearing aid was coupled with a television via Bluetooth using a streamer. The video recorded stimuli were presented at 65 dB SPL at normal rate, 35% compression and 45% compression conditions. Speech recognition scores and quality ratings were obtained for each condition with and without the Bluetooth streamer connected to the hearing aids. Results  Speech recognition scores were significantly better with Bluetooth coupling compared with conventional hearing aid use at 40% compressed speech rate. The quality was also rated higher in almost all parameters across speech rates when Bluetooth was used. Conclusions  The improved clarity and nullification of room reverberation offered by Bluetooth coupling can potentially compensate for the age-related temporal processing deficit contributing to ease of listening.

Aging-Related Decline in Phonated and Whispered Speech Perception Not Compensated For by Increased Duration and Intensity: Evidence From Mandarin-Speaking Adult Listeners

PURPOSE

This study aimed to examine how aging and modifications of critical acoustic parameters may affect the perception of whispered speech as a degraded signal.

METHOD

Forty Mandarin-speaking adults were included in the study. Part 1 of the study compared the perception of Mandarin lexical tones, vowels, and syllables in older and younger adults in whispered versus phonated speech conditions. Parts 2 and 3 further examined how modification of duration and intensity cues contributed to the perceptual outcomes.

RESULTS

Perception of whispered tones was compromised in older and younger adults. Older adults identified lexical tones less accurately than their younger counterparts, particularly for phonated T2 and T3 and whispered T3. Aging also negatively affected the vowel identification of /i, u/ in the whispered condition. Syllable-level accuracy was largely dependent on the accuracy of lexical tones and vowels. Furthermore, reduced duration led to the decreased accuracy of phonated T3 and whispered T2 and T3 but increased accuracy of phonated T4. Reduced intensity lowered the recognition accuracy for phonated vowels /i, ɤ, o, y/ in older adults and /i, u/ in younger adults, and it also lowered the accuracy of whispered vowels /a, ɤ/ in older adults. Contrary to our expectation, increased duration and intensity did not improve older adults' speech perception in either phonated or whispered conditions.

CONCLUSIONS

The results suggest that aging adversely affected speech perception in both phonated and whispered conditions with more challenges in identifying whispered speech for older adults. While older adults' diminished performance may be potentially due to problems with processing the degraded temporal and spectral information of the target speech sounds, it cannot be simply compensated for by increasing the duration and intensity of the target sounds beyond the audible level.

Improving older adults' understanding of challenging speech: Auditory training, rapid adaptation and perceptual learning

The literature surrounding auditory perceptual learning and auditory training for challenging speech signals in older adult listeners is highly varied, in terms of both study methodology and reported outcomes. In this review, we discuss some of the pertinent features of listener, stimulus, and training protocol. Literature regarding the elicitation of auditory perceptual learning for time-compressed speech, non-native speech, and noise-vocoded speech is reviewed, as are auditory training protocols designed to improve speech-in-noise recognition. The literature is synthesized to establish some over-arching findings for the aging population, including an intact capacity for auditory perceptual learning, but a limited transfer of learning to untrained stimuli.

Age, Hearing, and the Perceptual Learning of Rapid Speech

The effects of aging and age-related hearing loss on the ability to learn degraded speech are not well understood. This study was designed to compare the perceptual learning of time-compressed speech and its generalization to natural-fast speech across young adults with normal hearing, older adults with normal hearing, and older adults with age-related hearing loss. Early learning (following brief exposure to time-compressed speech) and later learning (following further training) were compared across groups. Age and age-related hearing loss were both associated with declines in early learning. Although the two groups of older adults improved during the training session, when compared to untrained control groups (matched for age and hearing), learning was weaker in older than in young adults. Especially, the transfer of learning to untrained time-compressed sentences was reduced in both groups of older adults. Transfer of learning to natural-fast speech occurred regardless of age and hearing, but it was limited to sentences encountered during training. Findings are discussed within the framework of dynamic models of speech perception and learning. Based on this framework, we tentatively suggest that age-related declines in learning may stem from age differences in the use of high- and low-level speech cues. These age differences result in weaker early learning in older adults, which may further contribute to the difficulty to perceive speech in daily conversational settings in this population.

Time-Compressed Speech Identification Is Predicted by Auditory Neural Processing, Perceptuomotor Speed, and Executive Functioning in Younger and Older Listeners

Older adults typically have difficulty identifying speech that is temporally distorted, such as reverberant, accented, time-compressed, or interrupted speech. These difficulties occur even when hearing thresholds fall within a normal range. Auditory neural processing speed, which we have previously found to predict auditory temporal processing (auditory gap detection), may interfere with the ability to recognize phonetic features as they rapidly unfold over time in spoken speech. Further, declines in perceptuomotor processing speed and executive functioning may interfere with the ability to track, access, and process information. The current investigation examined the extent to which age-related differences in time-compressed speech identification were predicted by auditory neural processing speed, perceptuomotor processing speed, and executive functioning. Groups of normal-hearing (up to 3000 Hz) younger and older adults identified 40, 50, and 60 % time-compressed sentences. Auditory neural processing speed was defined as the P1 and N1 latencies of click-induced auditory-evoked potentials. Perceptuomotor processing speed and executive functioning were measured behaviorally using the Connections Test. Compared to younger adults, older adults exhibited poorer time-compressed speech identification and slower perceptuomotor processing. Executive functioning, P1 latency, and N1 latency did not differ between age groups. Time-compressed speech identification was independently predicted by P1 latency, perceptuomotor processing speed, and executive functioning in younger and older listeners. Results of model testing suggested that declines in perceptuomotor processing speed mediated age-group differences in time-compressed speech identification. The current investigation joins a growing body of literature suggesting that the processing of temporally distorted speech is impacted by lower-level auditory neural processing and higher-level perceptuomotor and executive processes.

Transcranial alternating current stimulation modulates auditory temporal resolution in elderly people

Recent research provides evidence for a functional role of brain oscillations for perception. For example, auditory temporal resolution seems to be linked to individual gamma frequency of auditory cortex. Individual gamma frequency not only correlates with performance in between-channel gap detection tasks but can be modulated via auditory transcranial alternating current stimulation. Modulation of individual gamma frequency is accompanied by an improvement in gap detection performance. Aging changes electrophysiological frequency components and sensory processing mechanisms. Therefore, we conducted a study to investigate the link between individual gamma frequency and gap detection performance in elderly people using auditory transcranial alternating current stimulation. In a within-subject design, twelve participants were electrically stimulated with two individualized transcranial alternating current stimulation frequencies: 3 Hz above their individual gamma frequency (experimental condition) and 4 Hz below their individual gamma frequency (control condition), while they were performing a between-channel gap detection task. As expected, individual gamma frequencies correlated significantly with gap detection performance at baseline and in the experimental condition, transcranial alternating current stimulation modulated gap detection performance. In the control condition, stimulation did not modulate gap detection performance. In addition, in elderly, the effect of transcranial alternating current stimulation on auditory temporal resolution seems to be dependent on endogenous frequencies in auditory cortex: Elderlies with slower individual gamma frequencies and lower auditory temporal resolution profit from auditory transcranial alternating current stimulation and show increased gap detection performance during stimulation. Our results strongly suggest individualized transcranial alternating current stimulation protocols for successful modulation of performance.

Effects of hearing loss on speech recognition under distracting conditions and working memory in the elderly

Purpose

The current study aimed to evaluate hearing-related changes in terms of speech-in-noise processing, fast-rate speech processing, and working memory; and to identify which of these three factors is significantly affected by age-related hearing loss.

Methods

One hundred subjects aged 65–84 years participated in the study. They were classified into four groups ranging from normal hearing to moderate-to-severe hearing loss. All the participants were tested for speech perception in quiet and noisy conditions and for speech perception with time alteration in quiet conditions. Forward- and backward-digit span tests were also conducted to measure the participants’ working memory.

Results

1) As the level of background noise increased, speech perception scores systematically decreased in all the groups. This pattern was more noticeable in the three hearing-impaired groups than in the normal hearing group. 2) As the speech rate increased faster, speech perception scores decreased. A significant interaction was found between speed of speech and hearing loss. In particular, 30% of compressed sentences revealed a clear differentiation between moderate hearing loss and moderate-to-severe hearing loss. 3) Although all the groups showed a longer span on the forward-digit span test than the backward-digit span test, there was no significant difference as a function of hearing loss.

Conclusion

The degree of hearing loss strongly affects the speech recognition of babble-masked and time-compressed speech in the elderly but does not affect the working memory. We expect these results to be applied to appropriate rehabilitation strategies for hearing-impaired elderly who experience difficulty in communication.

Recognition of synthesized vowel sequences in steady-state and sinusoidally amplitude-modulated noises

Modulation masking is known to impact speech intelligibility, but it is not clear whether the mechanism underlying this phenomenon is an invariant, bottom-up process, or if it is subjected to factors such as perceptual segregation and stimulus uncertainty thereby showing a top-down component. In the main experiment of the current study (Exp. II), listeners' ability to recognize sequences of synthesized vowels (i.e., the target) in sinusoidally amplitude-modulated noises (i.e., the masker) was evaluated. The target and masker were designed to be perceptually distinct to limit the top-down component of modulation masking. The duration of each vowel was either 25 or 100 ms, the rate at which the vowels were presented was either 1 or 6 Hz, and the masker modulation rate was varied between 0.5 and 16 Hz. The selective performance degradation when the target and masker modulation spectra overlap, as would be expected from modulation masking, was not observed. In addition, these results were able to be adequately captured using a model of energetic masking without any modulation processing stages and fitted only using the vowel-recognition performance in steady-state maskers, as obtained from Exp. I. Results suggest that speech modulation masking might not be mediated through an early-sensory mechanism.

Comparison of Alternative Coupling Methods of the Vibrant Soundbridge Floating Mass Transducer

The active middle ear implant Vibrant Soundbridge© provides a variety of coupling modalities of the floating mass transducer (FMT) to various structures of the ossicular chain and the round window. A retrospective analysis was performed on 125 subjects (n = 137 ears) (1) to compare the efficacy of the different FMT coupling modalities with increasing degree of hearing loss, (2) to compare the performance in speech outcome and the effective gain between the coupling types, and (3) to evaluate the risk of additional hearing loss of each coupling procedure. The patients were grouped according to their type of FMT coupling into incus vibroplasty (incus group, n = 59), round window vibroplasty with coupler (RWC group, n = 23), round window vibroplasty without coupler (RW group, n = 22), and oval window vibroplasty with coupler (OWC group, n = 33). For each coupling group, pre- and postoperative thresholds, the results of the Freiburg monosyllable test at 65 dB SPL, and the effective gain across frequencies (0.5-6 kHz) were evaluated. A logistic regression function was used to describe the relationship between word recognition scores (WRS, in % correct) and the mean bone conduction (BC) hearing loss. The surgical procedure had no clinically relevant effect on BC thresholds of patients in each coupling group. The BC pure tone average (PTA4) for 50% WRS predicted by the model function was similar for the incus (48.2 dB nHL), RW (47.8 dB nHL), and OWC (49.0 dB nHL) groups, but higher for the RWC group (67.9 dB nHL). However, the median WRS was 80% or better with no significant differences in speech perception between coupling types (Kruskal-Wallis test, p = 0.229). The effective gain shows an advantage for the incus coupling between 0.5 and 2 kHz over the other coupling types. The performance of the FMT coupling modalities is equally good for patients with a mild-to-moderate hearing loss, but the efficacy of coupling types differs for patients with greater hearing loss (>48 dB BC HL).

The development and standardization of Self-assessment for Hearing Screening of the Elderly

Purpose

The present study aimed to develop and standardize a screening tool for elderly people who wish to check for themselves their level of hearing loss.

Methods

The Self-assessment for Hearing Screening of the Elderly (SHSE) consisted of 20 questions based on the characteristics of presbycusis using a five-point scale: seven questions covered general issues related to sensorineural hearing loss, seven covered hearing difficulty under distracting listening conditions, two covered hearing difficulty with fast-rated speech, and four covered the working memory function during communication. To standardize SHSE, 83 elderly participants took part in the study: 25 with normal hearing, and 22, 23, and 13 with mild, moderate, and moderate-to-severe sensorineural hearing loss, respectively, according to their hearing sensitivity. All were retested 3 weeks later using the same questionnaire to confirm its reliability. In addition, validity was assessed using various hearing tests such as a sentence test with background noise, a time-compressed speech test, and a digit span test.

Results

SHSE and its subcategories showed good internal consistency. SHSE and its subcategories demonstrated high test–retest reliability. A high correlation was observed between the total scores and pure-tone thresholds, which indicated gradually increased SHSE scores of 42.24%, 55.27%, 66.61%, and 78.15% for normal hearing, mild, moderate, and moderate-to-severe groups, respectively. With regard to construct validity, SHSE showed a high negative correlation with speech perception scores in noise and a moderate negative correlation with scores of time-compressed speech perception. However, there was no statistical correlation between digit span results and either the SHSE total or its subcategories. A confirmatory factor analysis supported three factors in SHSE.

Conclusion

We found that the developed SHSE had valuable internal consistency, test–retest reliability, and convergent and construct validity. These results suggest that SHSE is a reliable and valid measure to represent the degree of hearing loss in the elderly.

Hearing Impairment in Relation to Severity of Diabetes in a Veteran Cohort

OBJECTIVE

Type 2 diabetes is epidemic among veterans, approaching three times the prevalence of the general population. Diabetes leads to devastating complications of vascular and neurologic malfunction and appears to impair auditory function. Hearing loss prevention is a major health-related initiative in the Veterans Health Administration. Thus, this research sought to identify, and quantify with effect sizes, differences in hearing, speech recognition, and hearing-related quality of life (QOL) measures associated with diabetes and to determine whether well-controlled diabetes diminishes the differences.

DESIGN

The authors examined selected cross-sectional data from the baseline (initial) visit of a longitudinal study of Veterans with and without type 2 diabetes designed to assess the possible differences in age-related trajectories of peripheral and central auditory function between the two groups. In addition, the diabetes group was divided into subgroups on the basis of medical diagnosis of diabetes and current glycated hemoglobin (HbA1c) as a metric of disease severity and control. Outcome measures were pure-tone thresholds, word recognition using sentences presented in noise or time-compressed, and an inventory assessing the self-perceived impact of hearing loss on QOL. Data were analyzed from 130 Veterans ages 24 to 73 (mean 48) years with well-controlled (controlled) diabetes, poorly controlled (uncontrolled) diabetes, prediabetes, and no diabetes. Regression was used to identify any group differences in age, noise exposure history, and other sociodemographic factors, and multiple regression was used to model each outcome variable, adjusting for potential confounders. Results were evaluated in relation to diabetes duration, use of insulin (yes, no), and presence of selected diabetes complications (neuropathy and retinopathy).

RESULTS

Compared with nondiabetics, Veterans with uncontrolled diabetes had significant differences in hearing at speech frequencies, including poorer hearing by 3 to 3.5 dB for thresholds at 250 Hz and in a clinical pure-tone average, respectively. Compared with nondiabetic controls, individuals with uncontrolled diabetes also significantly more frequently reported that their hearing adversely impacted QOL on one of the three subscales (ability to adapt). Despite this, although they also had slightly poorer mean scores on both word recognition tasks performed, these differences did not reach statistical significance and all subjects performed well on these tasks. Compared with Veterans with controlled diabetes, those with uncontrolled disease tended to have had diabetes longer, be insulin-dependent, and have a greater prevalence of diabetic retinopathy. Results are generally comparable with the literature with regard to the magnitude of threshold differences and the prevalence of hearing impairment but extend prior work by providing threshold difference and hearing loss prevalence effect sizes by category of diabetes control and by including additional functional measures.

CONCLUSIONS

In a cohort of Veterans with type 2 diabetes and relatively good hearing, significant effects of disease severity were found for hearing thresholds at a subset of frequencies and for one of the three QOL subscales. Significant differences were concentrated among those with poorly controlled diabetes based on current HbA1c. Results provide evidence that the observed hearing dysfunction in type 2 diabetes might be prevented or delayed through tight metabolic control. Findings need to be corroborated using longitudinal assessments.

The effects of noise vocoding on gap detection thresholds

Gap detection threshold (GDT), the shortest silent interval a person can perceive, is a commonly used measure of temporal processing resolution. The purposes of this study were: (1) to examine the effects of noise vocoding, which has been used to simulate what signals sound like through a cochlear implant, on GDTs in normal-hearing subjects, and (2) to further the understanding of neural mechanisms underlying gap detection using the Auditory Late Response (ALR). Thirteen normal listeners participated. In behavioral tests, the GDTs were determined for the original and vocoded stimuli. In ALR recordings, the subjects were presented with auditory stimuli with and without containing gaps and stimuli with and without being vocoded. Results showed that GDTs were significantly elevated for vocoded stimuli with spectral resolutions of 4 and 20 channels compared to those for the original stimuli. A gap effect was observed in the post-gap ALR. Current densities for N1 peaks evoked by stimuli with zero- vs. non-zero ms gaps, pre- vs. post-gap markers, and original vs. vocoded stimuli were obtained using the standardized low-resolution brain electromagnetic tomography (sLORETA) method. Paired comparisons of pre- and post-gap current density values were made. Results showed a statistical difference between the N1s evoked by pre- vs. post-gap markers, with the activation in the middle frontal gyrus and precentral gyrus. The results suggest that: (1) noise vocoding does affect temporal processing resolution assessed with GDTs, (2) gap detection may involve the recruitment of cognitive neural resources, and (3) the ALR has a potential value of objectively estimating temporal processing resolution.

Effect of Repetition Rate on Speech Evoked Auditory Brainstem Response in Younger and Middle Aged Individuals

Speech evoked auditory brainstem responses depicts the neural encoding of speech at the level of brainstem. This study was designed to evaluate the neural encoding of speech at the brainstem in younger population and middle-aged population at three different repetition rates (6.9, 10.9 and 15.4). Speech evoked auditory brainstem response was recorded from 84 participants (young participants=42, middle aged participants=42) with normal hearing sensitivity. The latency of wave V and amplitude of the fundamental frequency, first formant frequency and second formant frequency was calculated. Results showed that the latency of wave V was prolonged for middle-aged individuals for all three-repetition rates compared to the younger participants. The results of the present study also revealed that there was no difference in encoding of fundamental frequency between middle aged and younger individuals at any of the repetition rates. However, increase in repetition rate did affect the encoding of the fundamental frequency in middle-aged individuals. The above results suggest a differential effect of repetition rate on wave V latency and encoding of fundamental frequency. Further, it was noticed that repetition rate did not affect the amplitude of first formant frequency or second formant frequency in middle aged participants compared to the younger participants.

Speech perception in older listeners with normal hearing:conditions of time alteration, selective word stress, and length of sentences

Background and Objectives

Deficits of the aging auditory system negatively affect older listeners in terms of speech communication, resulting in limitations to their social lives. To improve their perceptual skills, the goal of this study was to investigate the effects of time alteration, selective word stress, and varying sentence lengths on the speech perception of older listeners.

Subjects and Methods

Seventeen older people with normal hearing were tested for seven conditions of different time-altered sentences (i.e., ±60%, ±40%, ±20%, 0%), two conditions of selective word stress (i.e., no-stress and stress), and three different lengths of sentences (i.e., short, medium, and long) at the most comfortable level for individuals in quiet circumstances.

Results

As time compression increased, sentence perception scores decreased statistically. Compared to a natural (or no stress) condition, the selectively stressed words significantly improved the perceptual scores of these older listeners. Long sentences yielded the worst scores under all time-altered conditions. Interestingly, there was a noticeable positive effect for the selective word stress at the 20% time compression.

Conclusions

This pattern of results suggests that a combination of time compression and selective word stress is more effective for understanding speech in older listeners than using the time-expanded condition only.

The effects of semantic context and the type and amount of acoustic distortion on lexical decision by younger and older adults

PURPOSE

In this study, the authors investigated how acoustic distortion affected younger and older adults' use of context in a lexical decision task.

METHOD

The authors measured lexical decision reaction times (RTs) when intact target words followed acoustically distorted sentence contexts. Contexts were semantically congruent, neutral, or incongruent. Younger adults (n = 216) were tested on three distortion types: low-pass filtering, time compression, and masking by multitalker babble, using two amounts of distortion selected to control for word recognition accuracy. Older adults (n = 108) were tested on two amounts of time compression and one low-pass filtering condition.

RESULTS

For both age groups, there was robust facilitation by congruent contexts but minimal inhibition by incongruent contexts. Facilitation decreased as distortion increased. Older listeners had slower RTs than younger listeners, but this difference was smaller in congruent than in neutral or incongruent conditions. After controlling for word recognition accuracy, older listeners' RTs were slower in time-compressed than in low-pass filtering conditions, but younger listeners performed similarly in both conditions.

CONCLUSIONS

These RT results highlight the interdependence between bottom-up sensory and top-down semantic processing. Consistent with previous findings based on accuracy measures, compared with younger adults, older adults were disproportionately slowed when speech was time compressed but more facilitated by congruent contexts.

Vocabulary influences older and younger listeners' processing of dysarthric speech

This study examined younger (n = 16) and older (n = 16) listeners' processing of dysarthric speech-a naturally occurring form of signal degradation. It aimed to determine how age, hearing acuity, memory, and vocabulary knowledge interacted in speech recognition and lexical segmentation. Listener transcripts were coded for accuracy and pattern of lexical boundary errors. For younger listeners, transcription accuracy was predicted by receptive vocabulary. For older listeners, this same effect existed but was moderated by pure-tone hearing thresholds. While both groups employed syllabic stress cues to inform lexical segmentation, older listeners were less reliant on this perceptual strategy. The results were interpreted to suggest that individuals with larger receptive vocabularies, with their presumed greater language familiarity, were better able to leverage cue redundancies within the speech signal to form lexical hypothesis-leading to an improved ability to comprehend dysarthric speech. This advantage was minimized as hearing thresholds increased. While the differing levels of reliance on stress cues across the listener groups could not be attributed to specific individual differences, it was hypothesized that some combination of larger vocabularies and reduced hearing thresholds in the older participant group led to them prioritize lexical cues as a segmentation frame.

Effect of speaker age on speech recognition and perceived listening effort in older adults with hearing loss

PURPOSE

Older adults exhibit difficulty understanding speech that has been experimentally degraded. Age-related changes to the speech mechanism lead to natural degradations in signal quality. We tested the hypothesis that older adults with hearing loss would exhibit declines in speech recognition when listening to the speech of older adults, compared with the speech of younger adults, and would report greater amounts of listening effort in this task.

METHOD

Nineteen individuals with age-related hearing loss completed speech recognition and listening effort scaling tasks. Both were conducted in quiet, when listening to high- and low-predictability phrases produced by younger and older speakers, respectively.

RESULTS

No significant difference in speech recognition existed when stimuli were derived from younger or older speakers. However, perceived effort was significantly higher when listening to speech from older adults, as compared with younger adults.

CONCLUSIONS

For older individuals with hearing loss, natural degradations in signal quality may require greater listening effort. However, they do not interfere with speech recognition-at least in quiet. Follow-up investigation of the effect of speaker age on speech recognition and listening effort under more challenging noise conditions appears warranted.

Bilingual listeners' perception of temporally manipulated English passages

PURPOSE

The current study measured, objectively and subjectively, how changes in speech rate affect recognition of English passages in bilingual listeners.

METHOD

Ten native monolingual, 20 English-dominant bilingual, and 20 non-English-dominant bilingual listeners repeated target words in English passages at five speech rates (unprocessed, two expanded, and two compressed), in quiet and in noise. For noise conditions, performance was measured at a signal-to-noise ratio that was determined through an adaptive procedure to avoid ceiling and floor effects. Listeners also made subjective judgments of speech rate, speech clarity, and performance confidence.

RESULTS

In noise, stepwise improvement was observed as rate slowed down. A similar effect was not found in quiet. This pattern in performance was largely comparable across listener groups but was most robust in English-dominant listeners. Changes in speech rate and presence of noise significantly affected listeners' subjective ratings; however, no intergroup differences were observed for any of the subjective ratings.

CONCLUSIONS

Bilingual listeners benefited from slow speech rates, more evidently so in noise than in quiet. Their performance, however, did not reach a monolingual level, even at the most favorable rate. Nonetheless, all listeners reported comparable confidence when processing temporally manipulated English passages.

Speech recognition and temporal processing in middle-aged women

PURPOSE

This study was designed to examine speech understanding ability and temporal processing in middle-aged women with normal or near-normal pure-tone thresholds.

RESEARCH DESIGN

Speech understanding, temporal processing ability, and self-assessed hearing were measured in groups of younger and middle-aged females.

STUDY SAMPLE

Participants were younger and middle-aged females (n = 12 per group) with normal hearing through 4000 Hz bilaterally. Subjects were drawn from nonclinical populations.

DATA COLLECTION AND ANALYSIS

Speech understanding was measured in the presence of steady-state noise and competing speech, with and without perceived spatial separation of the target speech and masker. The Gaps-In-Noise (GIN) test (Musiek et al, 2005) was used to assess temporal resolution ability. In addition, subjects completed a questionnaire with several items from the Speech, Spatial, and Qualities of Hearing Scale (Gatehouse and Noble, 2004) to gauge their subjective ability to understand speech in complex listening situations. Data were analyzed via repeated-measures ANOVA and Pearson r correlations.

RESULTS

Results showed that the performance of the middle-aged subjects was significantly poorer than that of the younger participants in the presence of a spatially coincident speech masker. Although performance in this listening condition was unrelated to pure-tone thresholds, it was strongly correlated with scores on the GIN test. Speech understanding performance in the presence of a steady-state masker was related to high-frequency pure-tone thresholds.

CONCLUSIONS

These results suggest that some middle-aged women with little or no pure-tone hearing loss experience listening difficulty in complex environments. Results also suggest a strong relationship between temporal processing and speech understanding in certain competing speech situations.

Age effects in temporal envelope processing: speech unmasking and auditory steady state responses

OBJECTIVE

The purpose of this study was to determine whether temporal envelope processing is reduced in older listeners. Experiment 1 tested the hypothesis that older listeners exhibit reduced speech unmasking at higher modulation rates. Experiment 2 tested the hypothesis that auditory steady state response (ASSR) amplitudes are reduced in older listeners at high modulation rates.

DESIGN

Two groups of observers with relatively normal hearing (younger, mean age = 25.0 years and older, mean age = 68.7 years) participated in two experiments. Experiment 1 examined speech unmasking in modulated noise as a function of masker modulation rate (16 and 32 Hz) and target speech rate (normal and 33% time compressed). Experiment 2 measured ASSR amplitudes as a function of modulation rate (32 and 128 Hz) and carrier frequency (500 and 2000 Hz).

RESULTS

Experiment 1 indicated that older listeners show reduced speech unmasking for normal-rate speech and reduced recognition of rapid speech in steady noise. However, for rapid speech, there is no age effect for speech unmasking and no difference in the magnitude of masking release as a function of modulation rate. In general, effects of listener age and masker modulation rate on the magnitude of masking release are observed only for normal-rate speech. Experiment 2 showed that the ASSR amplitudes of older listeners are reduced for a 128-Hz modulation rate but not for a 32-Hz modulation rate, irrespective of carrier frequency.

CONCLUSION

These results suggest that the reduced speech unmasking seen in older listeners for relatively slow modulation rates is not caused by deficits in envelope processing but rather is associated with the more constrained redundancy of the speech material available during the masker minima. Deficits in temporal envelope processing are evident in advanced age but only for relatively high envelope frequencies.

Processing of fast speech by elderly listeners

This study investigates the relative contributions of auditory and cognitive factors to the common finding that an increase in speech rate affects elderly listeners more than young listeners. Since a direct relation between non-auditory factors, such as age-related cognitive slowing, and fast speech performance has been difficult to demonstrate, the present study took an on-line, rather than off-line, approach and focused on processing time. Elderly and young listeners were presented with speech at two rates of time compression and were asked to detect pre-assigned target words as quickly as possible. A number of auditory and cognitive measures were entered in a statistical model as predictors of elderly participants' fast speech performance: hearing acuity, an information processing rate measure, and two measures of reading speed. The results showed that hearing loss played a primary role in explaining elderly listeners' increased difficulty with fast speech. However, non-auditory factors such as reading speed and the extent to which participants were affected by increased rate of presentation in a visual analog of the listening experiment also predicted fast speech performance differences among the elderly participants. These on-line results confirm that slowed information processing is indeed part of elderly listeners' problem keeping up with fast language.

Are individual differences in speech reception related to individual differences in cognitive ability? A survey of twenty experimental studies with normal and hearing-impaired adults

This paper summarizes twenty studies, published since 1989, that have measured experimentally the relationship between speech recognition in noise and some aspect of cognition, using statistical techniques such as correlation or factor analysis. The results demonstrate that there is a link, but it is secondary to the predictive effects of hearing loss, and it is somewhat mixed across study. No one cognitive test always gave a significant result, but measures of working memory (especially reading span) were mostly effective, whereas measures of general ability, such as IQ, were mostly ineffective. Some of the studies included aided listening, and two reported the benefits from aided listening: again mixed results were found, and in some circumstances cognition was a useful predictor of hearing-aid benefit.

Investigation of perceptual constancy in the temporal-envelope domain

The ability to discriminate complex temporal envelope patterns submitted to temporal compression or expansion was assessed in normal-hearing listeners. An XAB, matching-to-sample-procedure was used. X, the reference stimulus, is obtained by applying the sum of two, inharmonically related, sinusoids to a broadband noise carrier. A and B are obtained by multiplying the frequency of each modulation component of X by the same time expansion/compression factor, alpha (alphain[0.35-2.83]). For each trial, A or B is a time-reversed rendering of X, and the listeners' task is to choose which of the two is matched by X. Overall, the results indicate that discrimination performance degrades for increasing amounts of time expansion/compression (i.e., when alpha departs from 1), regardless of the frequency spacing of modulation components and the peak-to-trough ratio of the complex envelopes. An auditory model based on envelope extraction followed by a memory-limited, template-matching process accounted for results obtained without time scaling of stimuli, but generally underestimated discrimination ability with either time expansion or compression, especially with the longer stimulus durations. This result is consistent with partial or incomplete perceptual normalization of envelope patterns.

Effect of age, presentation method, and learning on identification of noise-vocoded words

Noise vocoding was used to investigate the ability of younger and older adults with normal audiometric thresholds in the speech range to use amplitude envelope cues to identify words. In Experiment 1, four 50-word lists were tested, with each word presented initially with one frequency band and the number of bands being incremented until it was correctly identified by the listener. Both age groups required an average of 5.25 bands for 50% correct word identification and performance improved across the four lists. In Experiment 2, the same participants who completed Experiment 1 identified words in four blocked noise-vocoded conditions (16, 8, 4, 2 bands). Compared to Experiment 1, both age groups required more bands to reach the 50% correct word identification threshold in Experiment 2, 6.13, and 8.55 bands, respectively, with younger adults outperforming older adults. Experiment 3 was identical to Experiment 2 except the participants had no prior experience with noise-vocoded speech. Again, younger adults outperformed older adults, with thresholds of 6.67 and 8.97 bands, respectively. The finding of age effects in Experiments 2 and 3, but not in Experiment 1, seems more likely to be related to differences in the presentation methods than to experience with noise vocoding.

Recognition of time-compressed and natural speech with selective temporal enhancements by young and elderly listeners

PURPOSE

The goal of this experiment was to determine whether selective slowing of speech segments improves recognition performance by young and elderly listeners. The hypotheses were (a) the benefits of time expansion occur for rapid speech but not for natural-rate speech, (b) selective time expansion of consonants produces greater score increments than other forms of selective time expansion, and (c) older listeners benefit from time expansion of speech

METHOD

Participants (n=10-16 per group) were younger and older adults with normal hearing or with hearing loss. A repeated-measures design was used to assess recognition of sentence-length stimuli presented in 2 baseline speech rates: natural and 50% time compression. Selective time expansion of consonants, vowels, or pauses was applied to the natural-rate and time-compressed sentence-length stimuli.

RESULTS

Listeners showed excellent performance for natural-rate speech, regardless of time-expansion method. Recognition was significantly poorer for the time-compressed sentences, but performance by elderly listeners and listeners with hearing loss improved with selective time expansion, particularly when applied to consonant segments.

CONCLUSION

The findings support the hypothesis that older listeners and listeners with hearing impairment benefit from selective time expansion of consonants applied to rapid speech, without a corresponding decrement when applied to normal-rate speech.

Auditory performance characteristics of the Computerized Revised Token Test (CRTT)

PURPOSE

To assess the Computerized Revised Token Test (CRTT) performance of individuals with normal hearing under several intensity conditions and under several spectral and temporal perturbation conditions.

METHOD

Sixty normal-hearing listeners were randomly assigned to 1 of 3 groups. Group 1 provided performance-intensity information about CRTT performance using uncompressed acoustic stimuli. Groups 2 and 3 completed the CRTT using temporally and spectrally compressed and expanded stimuli. CRTT performance functions were plotted for each group.

RESULTS

Group 1 required minimal audibility to perform maximally on this task. As expected, Groups 2 and 3 showed significant differences across subtests, regardless of distortion condition. Mean differences in performance between successive conditions for Group 2 increased beyond 40% time compressed. There was 1 significant difference for the time-expanded condition. There were no differences across frequency compressed and expanded conditions.

CONCLUSION

Young listeners require limited signal gain on the CRTT to achieve maximum performance. Time and frequency compression and expansion results were consistent with previous findings with varying types of speech stimuli. The results have implications for administration and interpretation of the CRTT administered to persons from other populations and will help in the development of a normative database for the CRTT.

Age-related differences in discrimination of an interval separating onsets of successive tone bursts as a function of interval duration

The study measured listener sensitivity to increments in the inter-onset interval (IOI) separating pairs of successive 20-ms 4000-Hz tone pulses. A silent interval between the tone pulses was adjusted across conditions to create reference tonal IOI values of 25-600 ms. For each condition, a duration DL for increments of the tonal IOI was measured in listeners comprised of young normal-hearing adults and two groups of older adults with and without high-frequency hearing loss. Discrimination performance of all listeners was poorest for the shorter reference IOIs, and improved to stable levels for longer reference intervals exceeding about 200 ms. Temporal sensitivity of the young listeners was significantly better than that of the elderly listeners in each condition, with the largest age-related differences observed for the shortest reference interval. Age-related differences were also observed for duration DLs measured using single 4000-Hz tone bursts set to three reference durations in the range 50-200 ms. The tone DLs of all listeners were smaller than the corresponding tone-pair IOI DLs, particularly for the shorter reference stimulus durations. There were no significant performance differences observed between the older listeners with and without hearing loss for either discrimination task.

Effects of reverberation and filtering on speech rate judgment

This study investigated the effects of listening condition on speech rate judgment. Four listening conditions, in which a single sentence was presented at 21 speech rates ranging from 90 WPM to 250 WPM, were incorporated. These conditions included non-degraded, reverberation, band-pass filtered, and low-pass filtered conditions, each of which was selected to simulate listening conditions one might encounter in daily life. The participants were 20 young adults (20 to 40 years) with normal hearing. They were asked to make judgments of the rates of speech randomly presented in the four listening conditions using an equal-interval 5-step scale from too slow through too fast. Overall, speech rate was judged to be faster in the reverberant condition than in the other three conditions. These findings may have implications for auditory rehabilitation and counseling.

The effect of aging on event-related potentials and behavioral responses: Comparison of tonal, phonologic and semantic targets

OBJECTIVE

To investigate age-related changes in speech perception by measuring event-related potentials (ERPs) elicited by auditory stimuli varying in their linguistic characteristics from pure tones to words.

METHODS

ERPs were recorded from 64 subjects in three age groups (young, middle age and elderly) to auditory target stimuli, using an oddball paradigm. Three different tasks and stimuli were used: tonal, phonological and semantic.

RESULTS

N100 latency to tonal targets was significantly shorter than to both types of speech targets. P300 latency to tonal targets was significantly shorter than to phonological targets, which in turn was shorter than to semantic targets. P300 amplitude recorded to the speech targets was significantly larger over the left hemisphere than over the right hemisphere in the young subjects. However, the reverse pattern of asymmetry, favoring the right hemisphere was found in the elderly subjects. The pattern of the hemispheric distribution for the middle aged was somewhere in between the young and elderly.

CONCLUSIONS

The data indicate possible progressive changes in left-right asymmetry in language processing with aging.

SIGNIFICANCE

Findings may indicate an increased use of compensatory mechanisms for speech processing, or alternatively, an increased use of different generators as individuals age.

Effects of age and sequence presentation rate on temporal order recognition

The experiments examined the ability of younger and older listeners to identify the temporal order of sounds presented in tonal sequences. The stimuli were three-tone sequences that spanned two-octave frequency range, and listeners identified random permutations of tone order using labels of relative pitch. Some of the sequences featured uniform timing characteristics, and the sequence duty cycle was varied across conditions to examine the relative influence of tonal durations and intertone interval on recognition performance across a range of sequence presentation rates. Other stimulus sequences featured nonuniform timing with unequal tone durations and intertone intervals. The listeners were groups of younger and older persons with or without hearing loss. Results indicated that temporal order recognition was influenced primarily by sequence presentation rate, independent of tonal duration, tonal interval spacing, or sequence timing characteristics. The performance of older listeners was poorer than younger listeners, but the age-related recognition differences were independent of sequence presentation rate. There were no consistent effects of hearing loss on temporal ordering performance.

Age-related differences in identification and discrimination of temporal cues in speech segments

This study investigated age-related differences in sensitivity to temporal cues in modified natural speech sounds. Listeners included young noise-masked subjects, elderly normal-hearing subjects, and elderly hearing-impaired subjects. Four speech continua were presented to listeners, with stimuli from each continuum varying in a single temporal dimension. The acoustic cues varied in separate continua were voice-onset time, vowel duration, silence duration, and transition duration. In separate conditions, the listeners identified the word stimuli, discriminated two stimuli in a same-different paradigm, and discriminated two stimuli in a 3-interval, 2-alternative forced-choice procedure. Results showed age-related differences in the identification function crossover points for the continua that varied in silence duration and transition duration. All listeners demonstrated shorter difference limens (DLs) for the three-interval paradigm than the two-interval paradigm, with older hearing-impaired listeners showing larger DLs than the other listener groups for the silence duration cue. The findings support the general hypothesis that aging can influence the processing of specific temporal cues that are related to consonant manner distinctions.

Speech comprehension difficulties in older adults: cognitive slowing or age-related changes in hearing?

Speech comprehension declines more rapidly in older adults than in younger adults as speech rate increases. This effect is usually attributed to a slowing of brain function with age. Alternatively, this Age X Speed interaction could reflect the inability of the older adult's auditory system to cope with speed-induced stimulus degradation. When the authors speeded speech in a way that produced minimal degradation, both age groups were equally affected. However, when speech was speeded using other methods, word identification declined more in older than in younger adults. Hence, auditory decline rather than cognitive slowing may be responsible for older adults' poorer performance in speeded conditions.

Time-compressed visual speech and age: a first report

OBJECTIVE

The purpose of this research was to investigate the effects of age on the ability to identify temporally altered visual speech signals.

DESIGN

Two groups of adult lipreaders, older (N = 20) and younger (N = 15), were tested on perception of visual-only speech signals. Identification performance was measured for time-compressed, time-expanded, and unaltered versions of words with visual only speech.

RESULTS

An overall reduction in lipreading ability was observed as a function of age. However, in contrast to results with time-altered auditory speech, older adults did not show a disproportionate change to speeded or slowed visual speech.

CONCLUSIONS

The absence of age effects in the identification of temporally altered visual speech signals stands in contrast to the considerable evidence that older adults are disproportionately affected by temporal alterations of auditory speech signals. These results argue against a generalized slowing of information processing in older adults and instead point to modality specific changes in temporal processing abilities.

Effects of stimulus and noise rate variability on speech perception by younger and older adults

The present experiments examine the effects of listener age and hearing sensitivity on the ability to understand temporally altered speech in quiet when the proportion of a sentence processed by time compression is varied. Additional conditions in noise investigate whether or not listeners are affected by alterations in the presentation rate of background speech babble, relative to the presentation rate of the target speech signal. Younger and older adults with normal hearing and with mild-to-moderate sensorineural hearing losses served as listeners. Speech stimuli included sentences, syntactic sets, and random-order words. Presentation rate was altered via time compression applied to the entire stimulus or to selected phrases within the stimulus. Older listeners performed more poorly than younger listeners in most conditions involving time compression, and their performance decreased progressively with the proportion of the stimulus that was processed with time compression. Older listeners also performed more poorly than younger listeners in all noise conditions, but both age groups demonstrated better performance in conditions incorporating a mismatch in the presentation rate between target signal and background babble compared to conditions with matched rates. The age effects in quiet are consistent with the generalized slowing hypothesis of aging. Performance patterns in noise tentatively support the notion that altered rates of speech signal and background babble may provide a cue to enhance auditory figure-ground perception by both younger and older listeners.

Older adult performance on an altered version of the SSI test

The Synthetic Sentence Identification (SSI) test has been used extensively in investigations of reduced speech understanding skills in older adults. In this study the SSI test was altered by adding noise to the competing message and by administering practice lists and equivalent test lists, as well as versions of the test that have 4- and 12-s interstimulus intervals (ISIs), along with the standard 8-s ISI. The purpose was to determine the effect of these alterations on performance in a group of older adults with average pure-tone average 2 values less than 33 dB HL. Performance changed as a function of the ISI, with less rollover occurring for the 4-s ISI condition than the other 2 ISIs.

Contribution of speech rate to speech perception in multichannel cochlear implant users

This study describes the effect of speech rate (fast, 11 syllables per second; medium, 9 syllables per second; slow, 6 syllables per second) on speech perception in 10 cochlear implant users. The speech perception performance was evaluated on the basis of the percentage score of syllables that were correctly recalled in sentences composed of 4 to 6 words. The percentage scores at the fast, medium, and slow speech rates were 15.7%, 39.0%, and 56.0%, respectively. The effect of speech rate slowing was significant (p < .0001). Variations in the effect of speech rate slowing were observed in the cochlear implant users. The improvement of speech perception by speech rate slowing was significantly (p < .005) related to the word test score and the score at the fast speech rate. The results reveal that the rate of speech is an important factor in improving the speech perception of cochlear implant users.

The relationship between the intelligibility of time-compressed speech and speech in noise in young and elderly listeners

A conventional measure to determine the ability to understand speech in noisy backgrounds is the so-called speech reception threshold (SRT) for sentences. It yields the signal-to-noise ratio (in dB) for which half of the sentences are correctly perceived. The SRT defines to what degree speech must be audible to a listener in order to become just intelligible. There are indications that elderly listeners have greater difficulty in understanding speech in adverse listening conditions than young listeners. This may be partly due to the differences in hearing sensitivity (presbycusis), hence audibility, but other factors, such as temporal acuity, may also play a significant role. A potential measure for the temporal acuity may be the threshold to which speech can be accelerated, or compressed in time. A new test is introduced where the speech rate is varied adaptively. In analogy to the SRT, the time-compression threshold (or TCT) then is defined as the speech rate (expressed in syllables per second) for which half of the sentences are correctly perceived. In experiment I, the TCT test is introduced and normative data are provided. In experiment II, four groups of subjects (young and elderly normal-hearing and hearing-impaired subjects) participated, and the SRT's in stationary and fluctuating speech-shaped noise were determined, as well as the TCT. The results show that the SRT in fluctuating noise and the TCT are highly correlated. All tests indicate that, even after correction for the hearing loss, elderly normal-hearing subjects perform worse than young normal-hearing subjects. The results indicate that the use of the TCT test or the SRT test in fluctuating noise is preferred over the SRT test in stationary noise.

Sources of age-related recognition difficulty for time-compressed speech

Older people frequently show poorer recognition of rapid speech or time-compressed speech than younger listeners. The present investigation sought to determine if the age-related problem in recognition of time-compressed speech could be attributed primarily to a decline in the speed of information processing or to a decline in processing brief acoustic cues. The role of the availability of linguistic cues on recognition performance was examined also. Younger and older listeners with normal hearing and with hearing loss participated in the experiments. Stimuli were sentences, linguistic phrases, and strings of random words that were unmodified in duration or were time compressed with uniform time compression or with selective time compression of consonants, vowels, or pauses. Age effects were observed for recognition of unmodified random words, but not for sentences and linguistic phrases. Analysis of difference scores (unmodified speech versus time-compressed speech) showed age effects for time-compressed sentences and phrases. The forms of time compression that were notably difficult for older listeners were uniform time compression and selective time compression of consonants. Indeed, poor performance in recognizing uniformly time-compressed speech was attributed primarily to difficulty in recognizing speech that incorporated selective time compression of consonants. Hearing loss effects were observed also for most of the listening conditions, although these effects were independent of the aging effects. In general, the findings support the notion that the problems of older listeners in recognizing time-compressed speech are associated with difficulty in processing the brief, limited acoustic cues for consonants that are inherent in rapid speech.

Recognition of time-distorted sentences by normal-hearing and cochlear-implant listeners

This study evaluated the effects of time compression and expansion on sentence recognition by normal-hearing (NH) listeners and cochlear-implant (CI) recipients of the Nucleus-22 device. Sentence recognition was measured in five CI users using custom 4-channel continuous interleaved sampler (CIS) processors and five NH listeners using either 4-channel or 32-channel noise-band processors. For NH listeners, recognition was largely unaffected by time expansion, regardless of spectral resolution. However, recognition of time-compressed speech varied significantly with spectral resolution. When fine spectral resolution (32 channels) was available, speech recognition was unaffected even when the duration of sentences was shortened to 40% of their original length (equivalent to a mean duration of 40 ms/phoneme). However, a mean duration of 60 ms/phoneme was required to achieve the same level of recognition when only coarse spectral resolution (4 channels) was available. Recognition patterns were highly variable across CI listeners. The best CI listener performed as well as NH subjects listening to corresponding spectral conditions; however, three out of five CI listeners performed significantly poorer in recognizing time-compressed speech. Further investigation revealed that these three poorer-performing CI users also had more difficulty with simple temporal gap-detection tasks. The results indicate that limited spectral resolution reduces the ability to recognize time-compressed speech. Some CI listeners have more difficulty with time-compressed speech, as produced by rapid speakers, because of reduced spectral resolution and deficits in auditory temporal processing.