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.

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.

Tinnitus Handicap Inventory (THI) as a hearing aid outcome measure.

This study assessed the effects of hearing aids on the perception of tinnitus using the Tinnitus Handicap Inventory (THI). THI benefit scores (unaided-aided) were examined in relation to hearing aid benefit as measured with the Abbreviated Profile of Hearing Aid Benefit (APHAB) inventory. The THI benefit was also related to the users' ratings of overall satisfaction with their hearing aids. Thirty-four novice hearing aid users with complaints of hearing loss and tinnitus participated in the study. Outcome measures were obtained 6 weeks after the hearing aid fittings. The results showed that hearing aid use reduced tinnitus handicap significantly, but, typically, the effect was small. The association between overall satisfaction ratings and THI benefit scores was weak. In contrast, the overall satisfaction ratings were strongly related to benefit on the speech subscales (average of Ease of Communication, Reverberation, and Background Noise) but not on the Aversiveness subscale of the APHAB. The weak relationship observed between THI benefit and benefit on the speech subscales of the APHAB suggested that the two inventories were not redundant. The results of the study suggest that the THI can make a useful contribution to the overall profile of hearing aid benefit for new hearing aid users with tinnitus.

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.

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.

Intersyllabic movement timing in the fluent speech of stutterers with different disfluency levels.

The goal of this study was to identify possible differences in movement timing in the fluent speech of adult stutterers who show varying levels of speech disfluency. Strain gauge recordings of lip and jaw movements and electroglottographic recordings of laryngeal vibration were obtained in 31 subjects as they repeated simple speech utterances. Measures of the duration and variability of intersyllablic articulatory events were analyzed in relation to speech disfluency level and history of speech treatment. As expected, movement durations were longer in subjects who had been through speech treatment. No significant associations were observed between timing durations and disfluency level. However, more disfluent subjects tended to show reduced variability in timing durations, an effect that was independent of speech treatment. This finding is interpreted in relation to previous observations on control systems that show instability and disfunction in association with reduced output variability. When disfluency level was measured during physiologic testing, duration interacted with speech treatment, with more disfluent subjects in the treatment group showing increased durations in their fluent speech. This effect is attributed to volitional control intended to facilitate speech fluency.

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.