Patricia G. Stelmachowicz

Objective: Although numerous studies have investigated the effects of single-microphone digital noise-reduction algorithms for adults with hearing loss, similar studies have not been conducted with young hearing-impaired children. The goal of this study was to examine the effects of a commonly used digital noise-reduction scheme (spectral subtraction) in children with mild to moderately severe sensorineural hearing losses. It was hypothesized that the process of spectral subtraction may alter or degrade speech signals in some way. Such degradation may have little influence on the perception of speech by hearing-impaired adults who are likely to use contextual information under such circumstances. For young children who are still developing various language skills, however, signal degradation may have a more detrimental effect on the perception of speech. Design: Sixteen children (eight 5- to 7-yr-olds and eight 8- to 10-yr-olds) with mild to moderately severe hearing loss participated in this study. All participants wore binaural behind the ear hearing aids where noise-reduction processing was performed independently in 16 bands with center frequencies spaced 500 Hz apart up to 7500 Hz. Test stimuli were nonsense syllables, words, and sentences in a background of noise. For all stimuli, data were obtained with noise reduction (NR) on and off conditions. Results: In general, performance improved as a function of speech to noise ratio for all three speech materials. The main effect for stimulus type was significant and post hoc comparisons of stimulus type indicated that speech recognition was higher for sentences than that for both nonsense syllables and words, but no significant differences were observed between nonsense syllables and words. The main effect for NR and the two-way interaction between NR and stimulus type were not significant. Significant age group effects were observed, but the two-way interaction between NR and age group was not significant. Conclusions: Consistent with previous findings from studies with adults, results suggest that the form of NR used in this study does not have a negative effect on the overall perception of nonsense syllables, words, or sentences across the age range (5 to 10 yrs) and speech to noise ratios (0, +5, and +10 dB) tested.

Purpose Recent studies from the authors' laboratory have suggested that reduced audibility in the high frequencies (because of the bandwidth of hearing instruments) may play a role in the delays in phonological development often exhibited by children with hearing impairment. The goal of the current study was to extend previous findings on the effect of bandwidth on fricatives/affricates to more complex stimuli. Method Nine fricatives/affricates embedded in 2-syllable nonsense words were filtered at 5 and 10 kHz and presented to normal-hearing 6- to 7-year-olds who repeated words exactly as heard. Responses were recorded for subsequent phonetic and acoustic analyses. Results Significant effects of talker gender and bandwidth were found, with better performance for the male talker and the wider bandwidth condition. In contrast to previous studies, relatively small (5%) mean bandwidth effects were observed for /s/ and /z/ spoken by the female talker. Acoustic analyses of stimuli used in the previous and the current studies failed to explain this discrepancy. Conclusions It appears likely that a combination of factors (i.e., dynamic cues, prior phonotactic knowledge, and perhaps other unidentified cues to fricative identity) may have facilitated the perception of these complex nonsense words in the current study.

Objective: Previous studies from our laboratory have shown that a restricted stimulus bandwidth can have a negative effect upon the perception of the phonemes /s/ and /z/, which serve multiple linguistic functions in the English language. These findings may have important implications for the development of speech and language in young children with hearing loss because the bandwidth of current hearing aids generally is restricted to 6 to 7 kHz. The primary goal of the current study was to expand our previous work to examine the effects of stimulus bandwidth on a wide range of speech materials, to include a variety of auditory-related tasks, and to include the effects of background noise. Design: Thirty-two children with normal hearing and 24 children with sensorineural hearing loss (7 to 14 yr) participated in this study. To assess the effects of stimulus bandwidth, four different auditory tasks were used: 1) nonsense syllable perception, 2) word recognition, 3) novel-word learning, and 4) listening effort. Auditory stimuli recorded by a female talker were low-pass filtered at 5 and 10 kHz and presented in noise. Results: For the children with normal hearing, significant bandwidth effects were observed for the perception of nonsense syllables and for words but not for novel-word learning or listening effort. In the 10-kHz bandwidth condition, children with hearing loss showed significant improvements for monosyllabic words but not for nonsense syllables, novel-word learning, or listening effort. Further examination, however, revealed marked improvements for the perception of specific phonemes. For example, bandwidth effects for the perception of /s/ and /z/ were not only significant but much greater than that seen in the group with normal hearing. Conclusions: The current results are consistent with previous studies that have shown that a restricted stimulus bandwidth can negatively affect the perception of /s/ and /z/ spoken by female talkers. Given the importance of these phonemes in the English language and the tendency of early caregivers to be female, an inability to perceive these sounds correctly may have a negative impact on both phonological and morphological development.

The success of universal newborn hearing screening programs has created a need for a well-defined scientifically based approach to the selection and fitting of hearing aids with this population. Current hearing-aid technology is complex, requiring many decisions during the fitting process. Studies with adults have shown large individual differences in hearing-aid benefit, and subjective test techniques (often used to optimize the hearing aid fitting with adults) cannot be used with infants and young children.

Research from JAMA Otolaryngology–Head & Neck Surgery — The Importance of High-Frequency Audibility in the Speech and Language Development of Children With Hearing Loss

The goal of this study was to assess performance on a novel-word learning task by normal-hearing and hearing-impaired children for words varying in form (noun versus verb), stimulus level (50 versus 60 dB SPL), and number of repetitions (4 versus 6). It was hypothesized that novel-word learning would be significantly poorer in the subjects with hearing loss, would increase with both level and repetition, and would be better for nouns than verbs. Twenty normal-hearing and 11 hearing-impaired children (6 to 9 yr old) participated in this study. Each child viewed a 4-minute animated slide show containing 8 novel words. The effects of hearing status, word form, repetition, and stimulus level were examined systematically. The influence of audibility, word recognition, chronological age, and lexical development also were evaluated. After hearing the story twice, children were asked to identify each word from a set of four pictures. Overall performance was 60% for the normal-hearing children and 41% for the children with hearing loss. Significant predictors of performance were PPVT raw scores, hearing status, stimulus level, and repetitions. The variables age, audibility, word recognition scores, and word form were not significant predictors. Results suggest that a child's ability to learn new words can be predicted from vocabulary size, stimulus level, number of exposures, and hearing status. Further, the sensitivity to presentation level observed in this novel-word learning task suggests that this type of paradigm may be an effective tool for studying various forms of hearing aid signal processing algorithms.

At long last, universal hearing detection and intervention programs have been implemented in the majority of states across the nation and are identifying children with hearing loss at younger ages than ever before.

In this study, the influence of stimulus context and audibility on sentence recognition was assessed in 60 normal-hearing children, 23 hearing-impaired children, and 20 normal-hearing adults. Performance-intensity (PI) functions were obtained for 60 semantically correct and 60 semantically anomalous sentences. For each participant, an audibility index (AI) was calculated at each presentation level, and a logistic function was fitted to rau-transformed percent-correct values to estimate the SPL and AI required to achieve 70% performance. For both types of sentences, there was a systematic age-related shift in the PI functions, suggesting that young children require a higher AI to achieve performance equivalent to that of adults. Improvement in performance with the addition of semantic context was statistically significant only for the normal-hearing 5-year-olds and adults. Data from the hearing-impaired children showed age-related trends that were similar to those of the normal-hearing children, with the majority of individual data falling within the 5th and 95th percentile of normal. The implications of these findings in terms of hearing-aid fitting strategies for young children are discussed.