Linda M. Thibodeau

Performance of Monolingual and Bilingual Speakers of English and Spanish on the Synthetic Sentence Identification Test

Differences in the performance of adults with normal hearing were evaluated on the English and Spanish versions of the Synthetic Sentence Identification (SSI) test in the ipsilateral competing message (ICM) format. Previous work has shown that bilingual subjects perform significantly better on the Spanish version of the SSI at a –30 dB message-to-competition ratio (MCR). The previous investigators attributed this difference in performance to the existence of a greater number of pauses in the competing message of the Spanish version compared to the English version. In the present study, seven bilingual speakers and ten monolingual speakers each of English and Spanish completed two conditions—the standard competing message (SC) and the competing message mixed with speech noise (SC+N)—in order to reduce or eliminate the effect of pauses on performance. Bilingual subjects’ scores in each language were not significantly different from monolingual subjects’ scores. Scores from bilinguals were significantly bett...

Performance of hearing-impaired persons on auditory enhancement tasks

An auditory enhancement effect was evaluated in normal and hearing-impaired persons using a paradigm similar to that used by Viemeister and Bacon [J. Acoust. Soc. Am. 71, 1502-1507 (1982)]. Thresholds for a 2000-Hz probe were obtained in two forward-masking conditions: (1) the standard condition in which the masker was a four-component harmonic complex including 2000 Hz, and (2) the enhancing condition in which the same harmonic complex except for the exclusion of the 2000-Hz component preceded the four-component masker. In addition, enhancement for speech was evaluated by asking subjects to identify flat-spectrum harmonic complexes that were preceded by inverse vowel spectra. Finally, suppression effects were evaluated by measuring forward-masked thresholds for a 2000-Hz probe as a function of suppressor frequency added to a 2000-Hz masker. Across all subjects, there was evidence of enhancement and better vowel recognition in those persons who also demonstrated evidence of suppression; however, two of the normal-hearing persons demonstrated reduced enhancement yet normal suppression effects.

Comparison of Speech Recognition With Adaptive Digital and FM Remote Microphone Hearing Assistance Technology by Listeners Who Use Hearing Aids

PURPOSE The purpose of this study was to compare the benefits of 3 types of remote microphone hearing assistance technology (HAT), adaptive digital broadband, adaptive frequency modulation (FM), and fixed FM, through objective and subjective measures of speech recognition in clinical and real-world settings. METHOD Participants included 11 adults, ages 16 to 78 years, with primarily moderate-to-severe bilateral hearing impairment (HI), who wore binaural behind-the-ear hearing aids; and 15 adults, ages 18 to 30 years, with normal hearing. Sentence recognition in quiet and in noise and subjective ratings were obtained in 3 conditions of wireless signal processing. RESULTS Performance by the listeners with HI when using the adaptive digital technology was significantly better than that obtained with the FM technology, with the greatest benefits at the highest noise levels. The majority of listeners also preferred the digital technology when listening in a real-world noisy environment. The wireless technology allowed persons with HI to surpass persons with normal hearing in speech recognition in noise, with the greatest benefit occurring with adaptive digital technology. CONCLUSION The use of adaptive digital technology combined with speechreading cues would allow persons with HI to engage in communication in environments that would have otherwise not been possible with traditional wireless technology.

Hearing aid users benefit from induction loop when using digital cellular phones.

Objective Hearing aid users have recently been reported to experience problems with electromagnetic interference when using digital cellular phones. This study was undertaken to investigate the possible benefit of an induction loop system developed for use with some cellular phone models, and also to compare the possible benefit in two languages (Finnish and American English) as well as the benefit with two hearing aid technologies (analog versus digital). Design The study was performed in controlled laboratory conditions at two tertiary care hearing health care centers, one in Oulu, Finland and the other in Dallas, in the United States. The subjects were experienced users of behind-the-ear hearing aids and served as their own controls in three different listening conditions. Thirty-two eligible subjects (20 in Oulu and 12 in Dallas) participated in three test conditions: 1. call with a landline phone, 2. call with a digital cellular phone alone and 3. call with a digital cellular phone coupled to an induction loop. Results Sentence recognition scores and subjective judgments using a visual analog scale revealed the poorest results with the digital cellular phone alone. When the induction loop was used with the digital cellular phones, sentence recognition scores and the visual analog scale scores were comparable to the scores obtained with a landline phone. The mean sentence recognition score for analog hearing aids was 62.4% (95% confidence interval 50.2 to 74.6) with the landline phone, 12.6% (−1.6 to 26.9) with the digital cellular phone alone, and 63.3% (44.2 to 82.3) when using the digital cellular phone with the induction loop. For digital hearing aids, the sentence recognition scores were 62.4% (51.9 to 72.9), 37.4% (18.0 to 56.8) and 57.6% (39.0 to 76.2), respectively. There was no significant difference in performance between the two centers. However, when using the digital cellular phone alone, there was no drop in the sentence recognition scores with the few (N = 5) digital hearing aids in Dallas. The subjects ranked the digital cellular phone alone as the poorest test condition and the digital cellular phone with an induction loop as the best. Conclusions Induction loops appear to offer one possible solution for the incompatibility problem between hearing aids and digital cellular phones. However, the generalizability of the results must be viewed cautiously, because testing included only one induction loop and two digital cellular phone models.

Exploration of factors beyond audibility that may influence speech recognition

The effects of reduced ability to differentiate acoustic information on speech reception are difficult to separate from the effects of reduced absolute sensitivity. One possible way is to explore abilities to differentiate acoustic information while holding absolute sensitivity constant. Two auditory phenomena known as enhancement and suppression, which are thought to be related to speech reception ability, were evaluated in persons with normal absolute sensitivity who had either normal or reduced speech recognition in noise. Results of forward masking experiments do not support the notion that enhancement or suppression is reduced in persons with reduced speech recognition in noise. However, their pattern of performance differed from that of listeners with normal speech recognition in noise when the duration of certain complex maskers was varied.

Smartphone-based noise adaptive speech enhancement for hearing aid applications

It is well established that the presence of environmental noises has a negative impact on the performance of hearing aid devices. This paper addresses a noise adaptive speech enhancement solution for the purpose of improving the performance of hearing aid devices in noisy environments. Depending on three noise types of babble, machinery, and driving car, the parameters of a recently developed speech enhancement algorithm are appropriately adjusted to gain improved speech understanding performance in noisy environments. This solution is implemented on smartphone platforms as an app and interfaced with a hearing aid device. A clinical testing protocol is devised to evaluate the performance of the app in participants with normal hearing and hearing impairments. The clinical testing results have indicated that statistically significant improvement in speech understanding is gained between the unprocessed and processed conditions using the developed noise adaptive speech enhancement solution.

Auditory training of speech recognition with interrupted and continuous noise maskers by children with hearing impairment

Previous studies have indicated that individuals with normal hearing (NH) experience a perceptual advantage for speech recognition in interrupted noise compared to continuous noise. In contrast, adults with hearing impairment (HI) and younger children with NH receive a minimal benefit. The objective of this investigation was to assess whether auditory training in interrupted noise would improve speech recognition in noise for children with HI and perhaps enhance their utilization of glimpsing skills. A partially-repeated measures design was used to evaluate the effectiveness of seven 1-h sessions of auditory training in interrupted and continuous noise. Speech recognition scores in interrupted and continuous noise were obtained from pre-, post-, and 3 months post-training from 24 children with moderate-to-severe hearing loss. Children who participated in auditory training in interrupted noise demonstrated a significantly greater improvement in speech recognition compared to those who trained in continuous noise. Those who trained in interrupted noise demonstrated similar improvements in both noise conditions while those who trained in continuous noise only showed modest improvements in the interrupted noise condition. This study presents direct evidence that auditory training in interrupted noise can be beneficial in improving speech recognition in noise for children with HI.

The effects of selective consonant amplification on sentence recognition in noise by hearing-impaired listeners.

Weak consonants (e.g., stops) are more susceptible to noise than vowels, owing partially to their lower intensity. This raises the question whether hearing-impaired (HI) listeners are able to perceive (and utilize effectively) the high-frequency cues present in consonants. To answer this question, HI listeners were presented with clean (noise absent) weak consonants in otherwise noise-corrupted sentences. Results indicated that HI listeners received significant benefit in intelligibility (4 dB decrease in speech reception threshold) when they had access to clean consonant information. At extremely low signal-to-noise ratio (SNR) levels, however, HI listeners received only 64% of the benefit obtained by normal-hearing listeners. This lack of equitable benefit was investigated in Experiment 2 by testing the hypothesis that the high-frequency cues present in consonants were not audible to HI listeners. This was tested by selectively amplifying the noisy consonants while leaving the noisy sonorant sounds (e.g., vowels) unaltered. Listening tests indicated small (∼10%), but statistically significant, improvements in intelligibility at low SNR conditions when the consonants were amplified in the high-frequency region. Selective consonant amplification provided reliable low-frequency acoustic landmarks that in turn facilitated a better lexical segmentation of the speech stream and contributed to the small improvement in intelligibility.

Comparison of suppression across frequencies

Although much research has focused on the temporal, spectral, and intensity relationships between a masker and a suppressor, there has been little attention directed towards relative amounts of suppression in different frequency regions. The purpose of this experiment was to compare the magnitude of suppression at 500 and 2000 Hz in two forward‐masking experiments with seven normal‐hearing persons. In the first experiment, the threshold for a 10‐ms probe was determined as the bandwidth of a 400‐ms masker increased from 0.05 to 1.6 times the probe frequency. Suppression was determined by observing a decrease in threshold when the masker bandwidth exceeded the estimated critical band. In the second experiment, the threshold for a 10‐ms probe was obtained with a 400‐ms tonal masker in two conditions: masker‐alone and masker+suppressor. Suppressor frequencies ranged from 1.1 to 1.5 times the probe frequency. Suppression was indicated by a lower threshold in the masker+suppressor condition relative to that in ...

Suppressor duration effects in forward masking.

It has been shown that as the duration of a suppressor increases, the amount of suppression increases in experiments where the suppressor duration was equal to or less than the masker [D. L. Weber and D. M. Green, J. Acoust. Soc. Am. 64, 1392–1399 (1978); R. V. Shannon, ibid. 59, 1460–1470 (1976)]. This suggests that the degree of suppression may be related to the time of interaction between the masker and suppressor. The purpose of this experiment was to evaluate the effects of suppressor duration when the time of masker–suppressor interaction was held constant. Forward‐masked thresholds for the 2000‐Hz probe were measured with a 2000‐Hz masker only (M), and as a function of suppressor duration when the onset of the suppressor preceded the masker (M+S). When the suppressor preceded the masker by 200 ms, the amount of suppression was minimal or absent. The possibility that the threshold change resulted from increased masking by the longer duration suppressor was evaluated by measuring masked threshold for...