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.

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.

The effects of increasing consonant/vowel intensity ratio on speech loudness.

It was hypothesized that speech loudness may be primarily determined by the level of the vowel and that, as a consequence, high positive consonant/vowel intensity ratios (C/V ratios) could be tolerated by hearing-impaired listeners with possible improvement in intelligibility. The present study was concerned with the effects of high C/V ratios on the loudness of speech as a necessary first step prior to more detailed studies of loudness tolerance and intelligibility. Recordings of four CVC monosyllables were digitized and one of the consonants in each word was selected for amplification relative to a constant vowel level. For each word a set of seven tokens was prepared representing a range of C/V ratios from approximately -20 dB to 9 dB. The loudness of each token was obtained through a loudness matching task involving a standard word presented at 90 dB SPL. In addition, sets of nonspeech stimuli were created to approximate the C/V ratios represented in two of the monosyllables. Loudness of nonspeech tokens was obtained using the same loudness matching paradigm. It was found that high C/V ratios had no appreciable effect on speech loudness. (The nonspeech stimuli gave similar results, however, so it was not possible to conclude that speech was unique in that respect.) The findings in general are encouraging for the further study of the influence of C/V ratio on intelligibility and the eventual incorporation of C/V processing into digital hearing aids.

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.

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.

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.

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.

An evaluation of residue features as correlates of voice disorders.

Two experiments were conducted to assess the correlations of residue features with some perceptual properties of voice disorders. First, 90 samples of the vowel /a/ produced by patients with various vocal pathologies were analyzed to obtain the residue features, and severity judgments of these vowel samples were obtained. The results of linear multiple regression analysis indicated that the features were highly correlated with the severity ratings. Second, an attempt was made to correlate the residue features with voice qualities. The features were calculated for the vowel /a/ produced by patients with vocal nodules, vocal fold paralysis, and vocal polyps and by normal talkers. Each vowel sample was rated on ten scales of voice quality. The results revealed high correlations among the quality scales so that discrete subject groups could not be formed. Thus, residue features may be useful in assessing the degree of vocal impairment, but their use as correlates of voice quality must await further research.

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.

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.

Dimensions of consonant perception in normal and hearing-impaired listeners.

Judgments of consonant similarity were obtained from subjects who had normal hearing, high-frequency sensorineural hearing loss, or relatively flat sensorineural hearing loss. The individual differences model through program INDSCAL was used to derive a set of perceptual features empirically from the similarity judgments, and to group the subjects on the basis of strength of feature usage. The analysis revealed that sonorance was the dominant dimension in the similarity judgments of the subjects with high-frequency hearing losses, while sibilance tended to dominate the judgments of the subjects with flat audiometric configurations. The normal-hearing subjects tended to weight these two dimensions approximately equally. These differences in similarity judgments were observed based upon audiometric configuration, despite the fact that the two hearing-impaired groups were not unique in word-recognition ability.

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.

Threshold improvement and acoustic gain with hearing aids.

Aided speech reception thresholds were obtained from 20 hearing-impaired listeners with three hearing aids adjusted to confort settings, and with the aids adjusted to deliver 40 dB of acoustic gain. The aided speech reception threshold under each condition was substracted from the unaided speech reception threshold to yield a measure of threshold improvement. Threshold improvement and acoustic gain comparisons revealed that, at comfort setting, these two measures were quite similar. However, at the 40-dB gain setting, acoustic gain exceeded threshold improvement by an average of 5.6 dB. For the high-gain condition, it appeared that the threshold improvement obtained by subjects with relatively good unaided sensitivity was limited by the ambient noise in the test chamber.

Psychometric principles in the selection, interpretation, and evaluation of communication self-assessment inventories.

A variety of self-assessment inventories have been introduced in recent years for use with hearing-impaired patients. These instruments differ considerably, both conceptually and operationally. Audiologists, therefore, are faced with the task of selecting a test instrument that is appropriate to their patient population and testing purpose. This paper outlines the psychometric principles that guide the selection, interpretation, and evaluation of self-assessment inventories. The application of these principles to a specific clinical population is illustrated by three studies of the Hearing Performance Inventory (Giolas, Owens, Lamb, & Schubert, 1979) conducted at Walter Reed Army Medical Center (WRAMC).

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.

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.

Perception of synthetic visual consonant-vowel articulations.

Synthetic speech-like articulations were presented to adult subjects via the visual modality, following the classic categorical perception experimental paradigm (Liberman, Harris, Hoffman, & Griffith, 1957). Animations were generated on a computer-based graphics system. Stimuli consisted of representations of the syllables /ba/, /va/, and /wa/; as well as 6 linearly interpolated intermediate stimuli between each of the possible exemplar pairs, resulting in three 8-item continua. Three sets of observations were obtained for these stimuli. First, for each continuum, labeling data were obtained in which the subject assigned one or the other exemplar label to each of the stimuli. Next, ABX discrimination data were obtained for each continuum. In the final task, subjects assigned a rating of one through nine to each animation indicating the extent to which it was like the exemplar syllables. Although the labeling functions showed rather abrupt transitions from one response category to the other, the peaks in the discrimination functions did not coincide with the category boundaries. Further, the mean rating functions were relatively linear, and the distribution of rating responses revealed unimodal distributions whose peak locations differed depending on the stimulus.

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.

Phoneme boundaries in normal and hearing-impaired ears.

Two experiments are reported which explore variables that may complicate the interpretation of phoneme boundary data from hearing-impaired listeners. Fourteen synthetic consonant-vowel syllables comprising a/ba-da-ga/ continuum were used as stimuli. The first experiment examined the influence of presentation level and ear of presentation in normal-hearing subjects. Only small differences in the phoneme boundaries and labeling functions were observed between ears and across presentation levels. Thus monaural presentation and relatively high signal level do not appear to be complicating factors in research with hearing-impaired listeners, at least for these stimuli. The second experiment described a test procedure for obtaining phoneme boundaries in some hearing-impaired listeners that controlled for between-subject sources of variation unrelated to hearing impairment and delineated the effects of spectral shaping imposed by the hearing impairment on the labeling functions. Labeling data were obtained from unilaterally hearing-impaired listeners under three test conditions: in the normal ear without any signal distortion; in the normal ear listening through a spectrum shaper that was set to match the subject's suprathreshold audiometric configuration; and in the impaired ear. The reduction in the audibility of the distinctive acoustic/phonetic cues seemed to explain all or part of the effects of the hearing impairment on the labeling functions of some subjects. For many other subjects, however, other forms of distortion in addition to reduced audibility seemed to affect their labeling behavior.