Hearing loss is associated with gray matter differences in older adults at risk for and with Alzheimer's disease.

Using data from the COMPASS-ND study we investigated associations between hearing loss and hippocampal volume as well as cortical thickness in older adults with subjective cognitive decline (SCD), mild cognitive impairment (MCI), and Alzheimer's dementia (AD). SCD participants with greater pure-tone hearing loss exhibited lower hippocampal volume, but more cortical thickness in the left superior temporal gyrus and right pars opercularis. Greater speech-in-noise reception thresholds were associated with lower cortical thickness bilaterally across much of the cortex in AD. The AD group also showed a trend towards worse speech-in-noise thresholds compared to the SCD group.

Listening Comprehension and Listening Effort in the Primary School Classroom.

In the primary school classroom, children are exposed to multiple factors that combine to create adverse conditions for listening to and understanding what the teacher is saying. Despite the ubiquity of these conditions, there is little knowledge concerning the way in which various factors combine to influence listening comprehension and the effortfulness of listening. The aim of the present study was to investigate the combined effects of background noise, voice quality, and visual cues on children's listening comprehension and effort. To achieve this aim, we performed a set of four well-controlled, yet ecologically valid, experiments with 245 eight-year-old participants. Classroom listening conditions were simulated using a digitally animated talker with a dysphonic (hoarse) voice and background babble noise composed of several children talking. Results show that even low levels of babble noise interfere with listening comprehension, and there was some evidence that this effect was reduced by seeing the talker's face. Dysphonia did not significantly reduce listening comprehension scores, but it was considered unpleasant and made listening seem difficult, probably by reducing motivation to listen. We found some evidence that listening comprehension performance under adverse conditions is positively associated with individual differences in executive function. Overall, these results suggest that multiple factors combine to influence listening comprehension and effort for child listeners in the primary school classroom. The constellation of these room, talker, modality, and listener factors should be taken into account in the planning and design of educational and learning activities.

Masking-level differences in older adults: the effect of the level of the masking noise.

In Experiment 1, masking-level differences (MLDs) for a 500-Hz tone at five masker levels were obtained from younger and older adults. For both age groups, there were no reliable increases in MLD once the spectrum level of the masker exceeded 27 dB SPL. MLDs were larger for younger than for older adults over the range of masker levels tested. In Experiment 2, the levels of both the signal and the masker in one ear were attenuated by either 15 or 30 dB relative to their level in the other ear, which was fixed at a spectrum level of 47 dB SPL. MLDs for both age groups declined with increasing IAA and age-related differences were observed in all conditions. The findings of these experiments indicate that (1) age-related differences in MLDs exist even when the level of the masker is sufficiently high that older adults achieve their plateau performance, and (2) older listeners are not disadvantaged more than younger listeners by interaural differences in the level of the input.

Age-related changes in temporal resolution: envelope and intensity effects.

Gap-detection thresholds were determined for 10 younger and 10 older adults at two sensation levels (40 and 60 dB SL) for tone pips with Gaussian amplitude envelopes whose standard deviations were 0.5, 1, 1.5, and 2 ms. Gap-detection thresholds were larger for the older participants under all conditions. For all participants, gap-detection thresholds increased with the standard deviation of the Gaussian amplitude envelope, were relatively independent of sensation level, and were independent of the degree of hearing loss. Because spectral splatter decreases with increasing standard deviation of the Gaussian amplitude envelope, the age-related differences in gap-detection cannot be attributed to differences between how young and old listeners are affected by off-frequency cues. Furthermore, the consistent age difference in gap-detection at all amplitude envelope standard deviations was shown to be incompatible with the hypothesis that temporal integration time is longer for older listeners.

How young and old adults listen to and remember speech in noise.

Two experiments using the materials of the Revised Speech Perception in Noise (SPIN-R) Test [Bilger et al., J. Speech Hear. Res. 27, 32-48 (1984)] were conducted to investigate age-related differences in the identification and the recall of sentence-final words heard in a babble background. In experiment 1, the level of the babble was varied to determine psychometric functions (percent correct word identification as a function of S/N ratio) for presbycusics, old adults with near-normal hearing, and young normal-hearing adults, when the sentence-final words were either predictable (high context) or unpredictable (low context). Differences between the psychometric functions for high- and low-context conditions were used to show that both groups of old listeners derived more benefit from supportive context than did young listeners. In experiment 2, a working memory task [Daneman and Carpenter, J. Verb. Learn. Verb. Behav. 19, 450-466 (1980)] was added to the SPIN task for young and old adults. Specifically, after listening to and identifying the sentence-final words for a block of n sentences, the subjects were asked to recall the last n words that they had identified. Old subjects recalled fewer of the items they had perceived than did young subjects in all S/N conditions, even though there was no difference in the recall ability of the two age groups when sentences were read. Furthermore, the number of items recalled by both age groups was reduced in adverse S/N conditions. The resutls were interpreted as supporting a processing model in which reallocable processing resources are used to support auditory processing when listening becomes difficult either because of noise, or because of age-related deterioration in the auditory system. Because of this reallocation, these resources are unavailable to more central cognitive processes such as the storage and retrieval functions of working memory, so that "upstream" processing of auditory information is adversely affected.

Gap detection and the precedence effect in young and old adults.

Thresholds for detecting a gap between two Gaussian-enveloped (standard deviation = 0.5 ms), 2-kHz tones were determined in young and old listeners. The gap-detection thresholds of old adults were more variable and about twice as large as those obtained from young adults. Moreover, gap-detection thresholds were not correlated with audiometric thresholds in either group. Estimates of the width of the temporal window of young subjects, based on the detection of a gap between two tone pips, were smaller than those typically obtained when a relatively long duration pure tone is interrupted [Moore et al., J. Acoust. Soc. Am. 85, 1266-1275 (1989)]. Because the amount of time it takes to recover from an adapting stimulus is likely to affect gap detection thresholds [Glasberg et al., J. Acoust. Soc. Am. 81, 1546-1556 (1987)], smaller estimates of temporal window size would be expected in this paradigm if the amount of adaptation produced by the first tone pip was negligible. The larger gap-detection thresholds of old subjects indicate that they may have larger temporal windows than young subjects. The lack of correlation between audiometric and gap-detection thresholds indicates that this loss of temporal acuity is not related to the degree of sensorineural hearing loss. In a second experiment on the precedence effect using the same subjects, a Gaussian-enveloped tone was presented over earphones to the left ear followed by the same tone pip presented to the right ear. To more realistically approximate a sound field situation, the tone pip presented to each ear was followed 0.6 ms later by an attenuated version presented to the contralateral ear. The delay between the left- and right-ear tone-pips was varied and the transition point between hearing a single tone on the left, and hearing two such sounds in close succession (one coming from the left and the other from the right) was determined. The transition point in this experiment did not differ between young and old subjects nor were these transition points correlated with gap-detection thresholds. These results indicate that monaural temporal acuity and binaural echo suppression may be based on different processes.

The effect of interaural delay of the masker on masking-level differences in young and old adults.

Diotic (SoNo) thresholds and dichotic (S pi N pi tau) thresholds were measured for young and old adults using a 500-Hz pure-tone signal and broadband burst masking noise at 37 dB SPL/Hz. In the dichotic condition both the signal and the masker were phase reversed and the masker was presented with an interaural delay of 0.25, 0.5, 0.75, 1, 1.25, 1.5, 1.75, 2, 3, or 5 ms. Masking-level differences (MLDs) were determined by subtracting dichotic thresholds from diotic thresholds. The SoNo thresholds for the old subjects did not differ significantly from those for the young subjects; however, when MLDs were plotted as a function of delay, the pattern of results differed significantly between young and old subjects. This difference in pattern was completely accounted for in terms of a delay-line version of Durlach's equalization and cancellation (EC) model [N. I. Durlach, in Foundations of Modern Auditory Theory, edited by J. V. Tobias (Academic, New York, 1972); B. A. Schneider and P. M. Zurek, J. Acoust. Soc. Am. 86, 1756-1763 (1989)] by assuming that temporal jitter increases with internal delay in young subjects but that it does not vary with the amount of internal delay in old subjects.

Masking-level differences in the elderly: a comparison of antiphasic and time-delay dichotic conditions.

Four dichotic thresholds (S pi N0, S0 N pi, S0 N tau, and S pi N pi tau) were measured for young and old subjects using both burst and continuous broadband maskers. Masking-level differences (MLDs) were determined by subtracting dichotic thresholds from homophasic thresholds (S0 N0 or S pi N pi). The S0 N0 thresholds for the old subjects did not differ significantly from those for the young subjects in either the continuous or the burst masking noise conditions. The S pi N pi thresholds for the old subjects did not differ significantly from those for the young subjects in the continuous masking noise condition, but there was a significant age effect (3 dB) when burst masking noise was used. Both young and old subjects obtained larger MLDs in continuous masking noise than in burst masking noise. MLDs for old subjects were smaller than MLDs for young subjects by 4.3, 5.0, 2.7, and 1.6 dB in burst masking noise and by 4.9, 3.5, 2.5, and 1.4 dB in continuous masking noise, respectively in the S pi N0, S pi N pi tau, S0 N tau, and S0 N pi conditions. Four young subjects there was a hierarchy in the size of the MLD obtained in the four dichotic conditions, with the MLD being significantly larger in the S pi N0 and S pi N pi tau conditions; however, the size of the MLD was the same in all four conditions for the old subjects. Compared to young subjects, the performance of the old subjects was characterized by decreased ability to use homophasic cues in burst masking noise and decreased ability to use interaural difference cues. These findings were observed at four signal frequencies.

The design of CAST (Computer-Aided Speechreading Training).

The underlying theoretical assumptions, goals, design, and implementation of a Computer-Aided Speechreading Training system (CAST) are described as a case study in program design. This computerized speechreading assessment and training system simulates face-to-face intervention and is designed to be one component of a comprehensive aural rehabilitation program for preretirement adults with acquired mild-to-moderate hearing loss. The interactive, automated course consists of eight training lessons, each focusing on a particular viseme that is practiced by a modified discourse tracking method using viseme-specific texts. Three basic speechreading skills are emphasized: visual speech perception, use of linguistic redundancy, and use of feedback between message sender and receiver. These skills are evaluated separately by means of CAST tracking rate, receiver strategy, and inferred error type. Four example case assessments are provided to illustrate the potential applications of CAST as a standardizable rehabilitative tool. An independent program evaluation is provided in a companion paper (Gagné, Dinon, & Parsons, 1991). Comparisons between CAST, face-to-face tracking procedures, and natural discourse are presented and discussed with reference to theoretical and clinical issues in speechreading and program evaluation.

[Interactive Microcomputer Method of Lipreading (MIMILLE): an interactive microcomputerized method of lipreading]. / MIMILLE: une méthode interactive micro-informatisée de labio-lecture.

A computer-aided speechreading assessment and training system is presented. It is intended to be one component of a comprehensive aural rehabilitation program for preretirement adults with acquired mild-to-moderate hearing loss. Each lesson focuses on a different viseme which is practiced using the 'discourse tracking' method. The system allows the evaluation of the basic skills necessary for lipreading, i.e. good visual speech decoding and effective use of lingustic redundancy and transmitter feedback, by evaluating separately tracking rate, strategy, and types of errors.

Clinical evaluation of a two-channel amplitude compression hearing aid.

Twelve experienced hearing aid users with mild to moderate hearing loss used two new, commercially available behind-the-ear amplitude compression hearing aids for 1 month each. One aid was a single-channel device; the other was a two-channel aid. All subjects had used other compression aids for at least 1 year. Performance in real-life situations with the personal aid and the two trial aids was evaluated by the Hearing Performance Inventory (HPI). Another questionnaire probed subjective preference for the three aids and willingness to purchase each of the trial aids. The major HPI finding was an equal performance superiority for the two trial aids over the personal aid for half the subjects. The preference/purchase questionnaire results indicated that the two-channel aid had some sound quality advantages, but was unacceptable physically. The single-channel trial was clearly preferred over the personal and two-channel device.

Signal detection in industrial noise: effects of noise exposure history, hearing loss, and the use of ear protection.

The detection of one-third octave signals superimposed on backgrounds of steady-state and intermittent industrial noise of 84 dBA was investigated for observers with normal hearing or moderate to severe noise-induced hearing loss (NIHL). Variables included age, noise exposure history, configuration of the audiogram and the wearing of insert hearing protectors. Detection thresholds were obtained binaurally over headphones using a two- interval forced-choice procedure. For unprotected listening all observers showed a masked threshold of about 80 dBA for a one-third octave band cented at 3.15 kHz. Neither variation in noise exposure history nor configuration of the audiogram were significant factors. Using insert protectors in noise, observers with normal hearing showed an advantage on average of 3 dB. Those with NIHL gave masked detection thresholds greater than 100 dBA. Detection of a one-third octave band centred at 1 kHz by hearing-impaired observers with mild to moderate loss at 1 kHz was similar to that for normal observers. A model of the detection process was developed and evaluated.

Aural rehabilitation in a teaching hospital: evaluation and results.

More than 1,000 hearing-impaired adults who underwent hearing aid evaluations in a teaching hospital were followed for a minimum of 1 year. Questionnaires, which included over 300 clinical items, were developed for computer entry by audiological staff. This data was analyzed to obtain demographic information about the population and the effectiveness of the intervention. The program was evaluated in terms of criteria ranging from simple compliance with the recommendation to purchase an aid, attendance at scheduled follow-up appointments, adequacy of the amplification system, patient competence in handling the aid, frequency and duration of aid use, and benefit in specific listening situations. It can be concluded that simple compliance figures overestimate program success. Even 1 year after purchase many patients still had practical difficulties with the aid, and use and benefit patterns were still developing. Directions for program change have been determined as measurement of success has been more critically defined and goals for rehabilitation have broadened.

Management of hearing-impaired in-patients in an active treatment hospital.

Hearing loss is the most prevalent chronic disability in North America today. The incidence of hearing loss in hospitalized patients is even greater than the incidence in the general population (7%). Hearing-impaired patients may be found in any ward of a hospital. Even mild hearing loss can result in communication difficulty that can increase patient anxiety, decrease speed and accuracy of diagnosis, and reduce the effectiveness of rehabilitation. Three illustrative case studies and specific recommendations for improving the management of hearing-impaired patients are provided.

The effect of hearing protection on narrowband signal detection in industrial noise.

A method for evaluating the effectiveness of insert protectors at suprathreshold intensities was developed. Normal listeners and workers with clinically diagnosed, bilateral, noise-induced hearing loss attempted to detect a 1 or 3 kHz narrowband signal, 500 msec in duration. The signal was presented binaurally over headphones, either in quiet or against a background of industrial noise taped on site. The level of the noise was fixed at 84 dBA. The level of the signal was varied across blocks of 50 trials from near threshold to clearly audible. Comparisons were made between the detectability of the signal when insert protectors were worn, and listening without protection. The results indicated that in both normal and hearing impaired listeners the slopes of the psychometric functions were fairly steep, covering a range of only about 5 dB. The value of attenuation of the insert protector derived from the displacement of the function for listening in quiet with the protector, relative to listening with the open ear was constant throughout the range of suprathreshold signal intensities used. In 84 dBA of background noise normal subjects showed an improvement of about 3 dB when they wore protectors. By contrast the wearing of protectors in noise by hearing impaired listeners resulted in substantial decrements in signal detection.

A review of current approaches to aural rehabilitation.

Degree of hearing impairment is not directly related to hearing handicap or disability. Since the 1940s measures of peripheral auditory function have been the basis of hearing aid selection even though they provide no direct information on psychosocial, vocational, or educational handicap or disability or on rehabilitation needs. Rehabilitation beyond provision of the hearing aid has been limited and demands new approaches. The evolution of aural rehabilitation is based on the notion of its being an ongoing process, of communication as a behaviour which relies on the integration of many types of information, and of the individual as a total person with multi-faceted hearing needs.

Coarticulation effects in lipreading.

Normal-hearing and hearing-impaired subjects with good lipreading skills lipread videotaped material under visual-only conditions. V1CV2 utterances were used where V could be /i/, /ae/ or /u/ and C could be /p/, /t/, /k/, /ch/, /f/, /theta/, /sh/, /sh/ or /w/. Coarticulatory effects were present in these stimuli. The influence of phonetic context on lipreading scores for each V and C was analyzed in an effort to explain some of the variability in the visual perception of phonemes which was suggested by existing literature. Transmission of information for four phonetic features was also analyzed. Lipreading performance was nearly perfect for /p/, /f/, /w/, /theta/ and /u/. Lipreading performance on /t/, /k/, /ch/, /s/, /i/ and /ae/ depended on context. The features labial, rounded, and alveolar or palatal place of articulation were found to transmit more information to lipreaders than did the feature continuant. Variability in articulatory parameters resulting from coarticulatory effects appears to increase overall lipreading difficulty.

Use of telephone amplifying devices by the hearing-impaired.

Recommendations of telephone amplifying devices for the hearing-impaired are evaluated. Handset amplifiers and hearing aids are compared. Performance characteristics of the devices, clinical evaluation of patient benefit, and use of the devices by a representative group of patients are discussed. Need for follow-up and directions for future improvements of such devices are indicated.