Effects of amplification and speechreading on consonant recognition by persons with impaired hearing.

OBJECTIVE: This study sought to describe the consonant information provided by amplification and by speechreading, and the extent to which such information might be complementary when a hearing aid user can see the talker's face. DESIGN: Participants were 25 adults with acquired sensorineural hearing losses who wore the GN ReSound BT2 Personal Hearing System binaurally. Consonant recognition was assessed under four test conditions, each presented at an input level of 50 dB SPL: unaided listening without speechreading (baseline), aided listening without speechreading, unaided listening with speechreading, and aided listening with speechreading. Confusion matrices were generated for each of the four conditions to determine overall percent correct for each of 14 consonants, and information transmitted for place of articulation, manner of articulation, and voicing features. RESULTS: Both amplification and speechreading provided a significant improvement in consonant recognition from the baseline condition. Speech-reading provided primarily place-of-articulation information, whereas amplification provided information about place and manner of articulation, as well as some voicing information. CONCLUSIONS: Both amplification and speechreading provided place-of-articulation cues. The manner-of-articulation and voicing cues provided by amplification, therefore, were generally complementary to speechreading. It appears that the synergistic effect of combining the two sources of information can be optimized by amplification parameters that provide good audibility in the low-to-mid frequencies.

Speech recognition ability in noise and its relationship to perceived hearing aid benefit.

Hearing-impaired listeners with similar hearing losses may differ widely in their ability to understand speech in noise. Such individual susceptibility to noise may explain why patients obtain varying degrees of benefit from hearing aids. The chief purpose of this study was to determine if adaptive measures of unaided speech recognition in noise were related to hearing aid benefit. Additionally, the relationship between perceived hearing handicap and benefit from amplification was explored. Before being fit with hearing aids, 47 new hearing aid users completed a self-assessment measure of hearing handicap Then, unaided speech recognition ability was measured in quiet and in noise. Three months later, subjects completed a hearing aid benefit questionnaire. A weak relationship was observed between perceived hearing handicap and hearing aid benefit. There were no significant relationships between speech-in-noise measures and hearing aid benefit, suggesting that speech recognition ability in noise is not a major determinant of the benefit derived from amplification.

Hearing aid benefit in patients with high-frequency hearing loss.

Patients with hearing loss limited to frequencies above 2 kHz are often considered borderline candidates for hearing aids. In this study, we used the Profile of Hearing Aid Benefit to access 134 patients' perceived benefit with a variety of linear hearing aids, some more capable than others at achieving prescribed frequency gain targets. We also sought to explore various audiologic and subject factors that might have led patients to report different degrees of success or failure with their hearing aids. Results demonstrate that subjects with hearing loss limited to frequencies above 2 kHz benefit significantly from amplification. However, the amount of benefit reported is mostly unrelated to the hearing aid gain and frequency response. Of numerous audiologic and demographic factors explored in the present study, the number of hours of hearing aid use per day turned out to be the most important single factor that was significantly related to the amount of reported hearing aid benefit. However, the predictive value of knowing how many hours per day subjects wore their aids, or any other combination of factors explored, was quite limited and only accounted for a small amount of the variability observed in user benefit.

The role of magnesium in the susceptibility of soldiers to noise-induced hearing loss.

A number of studies have demonstrated that magnesium, administered prophylactically, can reduce the amount of hearing loss resulting from noise exposure. This study explored the possible role of naturally occurring body magnesium concentration in susceptibility of soldiers to noise-induced hearing loss. Participants were 68 adult males who had received extensive noise exposure over several years as a result of training with weapon systems. Each participant provided a pure-tone audiogram, blood sample, and noise-exposure history. A variety of pure-tone indices was correlated with serum magnesium levels as determined by atomic absorption spectroscopy. No significant correlations were observed between any audiometric index and body magnesium. The results of this study, therefore, do not support the hypothesis that there is a strong association between naturally occurring body magnesium and susceptibility to noise-induced hearing loss.

Comparison of benefits provided by different hearing aid technologies.

The performance of 40 hearing-impaired adults with the GN ReSound digital BZ5 hearing instrument was compared with performance with linear hearing aids with input compression limiting (AGC-I) or two-channel analog wide dynamic range compression (WDRC) instruments. The BZ5 was evaluated with an omnidirectional microphone, dual-microphone directionality, and a noise reduction circuit in combination with dual-microphone directionality. Participants were experienced hearing aid users who were wearing linear AGC-I or analog WDRC instruments at the time of enrolment. Performance was assessed using the Connected Speech Test (CST) presented at several presentation levels and under various conditions of signal degradation and by the Profile of Hearing Aid Benefit (PHAB). Subjective ratings of speech understanding, listening comfort, and sound quality/naturalness were also obtained using 11-point interval scales. Small performance advantages were observed for WDRC over linear AGC-I, although WDRC did not have to be implemented digitally for these performance advantages to be realized. Substantial performance advantages for the dual microphones over the omnidirectional microphone were observed in the CST results in noise, but participants generally did not perceive these large advantages in everyday listening. The noise reduction circuit provided improved listening comfort but little change in speech understanding.

A clinical trial of the ReSound IC4 hearing device.

A manufacturer-sponsored clinical trial was conducted of ReSound Corporation's IC4 hearing device (HD), an in-the-ear application of their two-channel, fast-acting, wide-dynamic range compression sound processor. This study was a follow-up to an earlier clinical trial of ReSound's behind-the-ear version of the same sound processor, the BT2 Personal Hearing System (Walden, B. E., Surr, R. K., Cord, M. T., & Pavlovic, C. V. (1998). A clinical trial of the ReSound BT2 Personal Hearing System. American Journal of Audiology, 7, 85-100). Forty adult males with gradually sloping, moderate sensorineural hearing losses participated. All were experienced hearing aid users who wore linear Class D instruments with input compression limiting at the time of their enrollment in this study. The Connected Speech Test, presented at several presentation levels and under various conditions of signal degradation, and the scales and subscales of the Profile of Hearing Aid Benefit were used to evaluate hearing aid performance and benefit under four relatively independent prototype listening situations (Walden, B. E., Demorest, M. E., & Hepler, E. L. (1984). Self-report approach to assessing benefit derived from amplification. Journal of Speech and Hearing Research, 27, 49-56). Aided performance with the IC4 HD was compared with (a) unaided performance, (b) performance of persons with normal hearing, and (c) performance with linear amplification. Participants with hearing loss obtained significant benefit from the IC4 HD, although IC4-aided performance remained well below that of unaided performance of persons with normal hearing, especially on laboratory measures of speech recognition. Furthermore, small mean performance advantages were observed for the IC4 HD compared to linear hearing aids, although there was substantial variability across participants. Finally, when given a choice to either purchase the IC4 HD at a discount from the manufacturer or continue using their own government-issued linear hearing aids, the majority of the participants chose to purchase the IC4 HD.

Long-term versus short-term hearing aid benefit.

This study compared hearing aid benefit obtained 6 weeks and a minimum of 1 year after fitting to determine if changes occurred over time. Fifteen individuals with mild-to-moderate sensorineural hearing losses, who were successful users of linear amplification, were fitted binaurally with the Resound BT2 Personal Hearing System. These hearing aids are programmable in two frequency bands that provide wide dynamic range compression (WDRC) amplification. The manufacturer's recommended loudness growth in octave bands (LGOB) and audiogram programming algorithm and fitting procedures were used. Following an initial 6-week period and again following a minimum of 1 year of use, the Profile of Hearing Aid Benefit (PHAB) was administered. Similarly, speech recognition performance was tested using the Connected Speech Test (CST) in a six-talker speech babble at 50 dBA, +10 signal-to-noise (S/N); 60 dBA, +5 SNR; and 70 dBA, +2 SNR; and in quiet with a reverberation time of 0.78 seconds. Significant aided benefit was shown. These short-term benefit scores for the PHAB and CST were compared with those obtained after 1 year of full-time use. Results revealed no significant change in hearing aid benefit with long-term use, suggesting that a 6-week acclimatization period is sufficiently long for clinical trials of this type of WDRC amplification.

Auditory-visual speech recognition by hearing-impaired subjects: consonant recognition, sentence recognition, and auditory-visual integration.

Factors leading to variability in auditory-visual (AV) speech recognition include the subject's ability to extract auditory (A) and visual (V) signal-related cues, the integration of A and V cues, and the use of phonological, syntactic, and semantic context. In this study, measures of A, V, and AV recognition of medial consonants in isolated nonsense syllables and of words in sentences were obtained in a group of 29 hearing-impaired subjects. The test materials were presented in a background of speech-shaped noise at 0-dB signal-to-noise ratio. Most subjects achieved substantial AV benefit for both sets of materials relative to A-alone recognition performance. However, there was considerable variability in AV speech recognition both in terms of the overall recognition score achieved and in the amount of audiovisual gain. To account for this variability, consonant confusions were analyzed in terms of phonetic features to determine the degree of redundancy between A and V sources of information. In addition, a measure of integration ability was derived for each subject using recently developed models of AV integration. The results indicated that (1) AV feature reception was determined primarily by visual place cues and auditory voicing + manner cues, (2) the ability to integrate A and V consonant cues varied significantly across subjects, with better integrators achieving more AV benefit, and (3) significant intra-modality correlations were found between consonant measures and sentence measures, with AV consonant scores accounting for approximately 54% of the variability observed for AV sentence recognition. Integration modeling results suggested that speechreading and AV integration training could be useful for some individuals, potentially providing as much as 26% improvement in AV consonant recognition.

Comparison of linear and K-Amp circuits.

OBJECTIVE: To evaluate hearing aid user preference for Linear Class D or Class D with K-Amp circuit. DESIGN: Eighteen subjects, experienced with Class A hearing aid use, were given a choice of binaural hearing aids with either Linear Class D circuits or Class D with K-Amp circuits after consecutive 30 day trial periods with each set of instruments. The patients also rated the benefit obtained from each circuit using the Profile of Hearing Aid Benefit (PHAB). RESULTS: There was no significant difference in the number of subjects who chose one or the other of the circuits. Further, the PHAB scores showed no statistically significant differences between the two circuits. In most cases, the instruments rated highest on each of the subscales by an individual subject were also the ones preferred based on the 30 day trial. CONCLUSIONS: Hearing aids with either Class D Linear or Class D with K-Amp circuits provided significant benefit in many everyday listening environments for individuals with a mild to moderate degree of hearing loss. Subjective choice between the Linear Class D and the K-Amp circuits was relatively evenly divided.

Evaluating the articulation index for auditory-visual consonant recognition.

Adequacy of the ANSI standard for calculating the articulation index (AI) [ANSI S3.5-1969 (R1986)] was evaluated by measuring auditory (A), visual (V), and auditory-visual (AV) consonant recognition under a variety of bandpass-filtered speech conditions. Contrary to ANSI predictions, filter conditions having the same auditory AI did not necessarily result in the same auditory-visual AI. Low-frequency bands of speech tended to provide more benefit to AV consonant recognition than high-frequency bands. Analyses of the auditory error patterns produced by the different filter conditions showed a strong negative correlation between the degree of A and V redundancy and the amount of benefit obtained when A and V cues were combined. These data indicate that the ANSI auditory-visual AI procedure is inadequate for predicting AV consonant recognition performance under conditions of severe spectral shaping.

Spectral distribution of prosodic information.

Prosodic speech cues for rhythm, stress, and intonation are related primarily to variations in intensity, duration, and fundamental frequency. Because these cues make use of temporal properties of the speech waveform they are likely to be represented broadly across the speech spectrum. In order to determine the relative importance of different frequency regions for the recognition of prosodic cues, identification of four prosodic features, syllable number, syllabic stress, sentence intonation, and phrase boundary location, was evaluated under six filter conditions spanning the range from 200-6100 Hz. Each filter condition had equal articulation index (AI) weights, AI = 0.01; p(C)isolated words approximately equal to 0.40. Results obtained with normally hearing subjects showed that there was an interaction between filter condition and the identification of specific prosodic features. For example, information from high-frequency regions of speech was particularly useful in the identification of syllable number and stress, whereas information from low-frequency regions was helpful in identifying intonation patterns. In spite of these spectral differences, overall listeners performed remarkably well in identifying prosodic patterns, although individual differences were apparent. For some subjects, equivalent levels of performance across the six filter conditions were achieved. These results are discussed in relation to auditory and auditory-visual speech recognition.

The relationship of hearing-loss severity to demographic, age, treatment, and intervention-effectiveness variables.

The purpose of this study was to demonstrate how hearing-loss severity and the variables of demographics, age, treatment, and intervention effectiveness were related for 2519 children served by SKI*HI home-based programs between July 1979 and June 1991. Relationships between hearing-loss severity and demographic variables were negligible to small. Severity was inversely associated with identification, amplification, and program-start ages. The relationship between severity and early versus late program start was small; this was also true for the relationship between severity and communication methodology. Severity was positively associated with treatment duration; however, severity was not associated with treatment density. Intervention effectiveness for the severity levels, based on expressive and receptive language scores, was examined using three predictive models. These included the residuals between actual and predicted posttest scores, proportional change indices, and value-added gains per month. The usefulness of the three procedures for clinical and program-evaluation purposes is discussed.

Benefit from visual cues in auditory-visual speech recognition by middle-aged and elderly persons.

The benefit derived from visual cues in auditory-visual speech recognition and patterns of auditory and visual consonant confusions were compared for 20 middle-aged and 20 elderly men who were moderately to severely hearing impaired. Consonant-vowel nonsense syllables and CID sentences were presented to the subjects under auditory-only, visual-only, and auditory-visual test conditions. Benefit was defined as the difference between the scores in the auditory-only and auditory-visual conditions. The results revealed that the middle-aged and elderly subjects obtained similar benefit from visual cues in auditory-visual speech recognition. Further, patterns of consonant confusions were similar for the two groups.

Do adaptive frequency response (AFR) hearing aids reduce 'upward spread' of masking?

Speech recognition scores in noise are improved for some subjects who wear hearing aids that reduce low-frequency noise with an adjustable high-pass filter circuit. To evaluate whether these improvements were related to a reduction in upward spread of masking, pure-tone masking patterns for a low-frequency band-pass noise were measured in normal and hearing-impaired subjects. The filter skirt of the noise masker was very steep, with attenuation above the 1000 Hz cutoff greater than 120 dB per octave. Masking patterns for the same noise were also obtained in the presence of a high-pass filter that simulated the effects of an adaptive frequency response (AFR) hearing aid. Differences in the masking patterns were considered a measure of upward spread of masking. On average, subjects with high-frequency hearing loss demonstrated greater amounts of upward spread of masking than did normal-hearing listeners. Further, monosyllabic speech recognition in noise testing indicated improvements in performance of the hearing-impaired subjects related to the decrease of upward spread of masking in the high-pass filtering conditions.

Visual biasing of normal and impaired auditory speech perception.

Intersensory biasing occurs when cues in one sensory modality influence the perception of discrepant cues in another modality. Visual biasing of auditory stop consonant perception was examined in two related experiments in an attempt to clarify the role of hearing impairment on susceptibility to visual biasing of auditory speech perception. Fourteen computer-generated acoustic approximations of consonant-vowel syllables forming a /ba-da-ga/ continuum were presented for labeling as one of the three exemplars, via audition alone and in synchrony with natural visual articulations of /ba/ and of /ga/. Labeling functions were generated for each test condition showing the percentage of /ba/, /da/, and /ga/ responses to each of the 14 synthetic syllables. The subjects of the first experiment were 15 normal-hearing and 15 hearing-impaired observers. The hearing-impaired subjects demonstrated a greater susceptibility to biasing from visual cues than did the normal-hearing subjects. In the second experiment, the auditory stimuli were presented in a low-level background noise to 15 normal-hearing observers. A comparison of their labeling responses with those from the first experiment suggested that hearing-impaired persons may develop a propensity to rely on visual cues as a result of long-term hearing impairment. The results are discussed in terms of theories of intersensory bias.

Constancy of relative timing for stutterers and nonstutterers.

Fifteen stutterers and 15 nonstutterers read a 120-word passage five times in succession. From the stutterers' readings, sentences were selected for analysis that were produced fluently in the first and the fifth reading. The sentences surrounding the target utterance in the first reading, however, contained instances of stuttering although the surrounding sentences in the fifth reading were fluent. The same utterances were selected from the first and fifth readings produced by the nonstutterers, but the surrounding sentences were fluent for both samples. Four separate relative timing ratios were defined by measuring an acoustic period and an acoustic latency and dividing the period by the latency. Analysis of the ratios revealed no significant differences between the groups in spite of the rate changes that occurred between the readings. The data indicate that not all aspects of a stutterer's speech are affected by the stuttering, and that relative timing may be a critical parameter for the production of fluent utterances.

The tricyclic trimipramine in the treatment of subjective tinnitus.

We examined 26 consecutive patients with subjective tinnitus. All subjects were treated with the tricyclic antidepressant trimipramine in a double-blind study, each subject acting as his own control. All subjects were evaluated with pure tone audiometry, site of lesion testing, and auditory brain stem evoked response. The tinnitus assessment consisted of frequency and intensity matching, the determination of masking levels, and a subjective evaluation of severity. Plasma levels of trimipramine were monitored at regular intervals, and the Zung and Millon inventories were administered at the beginning and end of each study period. Nineteen subjects completed the study. Within the trimipramine group, one reported complete disappearance of his tinnitus, eight reported improvement, three no change, and seven that tinnitus was worse. Within the placebo group, eight reported improvement, seven no change, and four that tinnitus was worse. The natural history of tinnitus is such that what has been observed may reflect the evolution of the disease itself, rather than the effect of treatment. We feel that while tricyclics may not have been shown to be effective, the placebo effect played a significant role in the results obtained.