Recent studies with adults have suggested that amplification at 4 kHz and above fails to improve speech recognition and may even degrade performance when high-frequency thresholds exceed 50-60 dB HL. This study examined the extent to which high frequencies can provide useful information for fricative perception for normal-hearing and hearing-impaired children and adults. Eighty subjects (20 per group) participated. Nonsense syllables containing the phonemes /s/, /f/, and /O/, produced by a male, female, and child talker, were low-pass filtered at 2, 3, 4, 5, 6, and 9 kHz. Frequency shaping was provided for the hearing-impaired subjects only. Results revealed significant differences in recognition between the four groups of subjects. Specifically, both groups of children performed more poorly than their adult counterparts at similar bandwidths. Likewise, both hearing-impaired groups performed more poorly than their normal-hearing counterparts. In addition, significant talker effects for /s/ were observed. For the male talker, optimum performance was reached at a bandwidth of approximately 4-5 kHz, whereas optimum performance for the female and child talkers did not occur until a bandwidth of 9 kHz.

Results suggest that early-identified children are delayed in consonant and syllable structure development, which may influence early word learning rates. Fricative/affricate development appears to be challenging for some infants with hearing loss. This may be related to the effects of sensorineural hearing loss on high-frequency information, restricted bandwidth provided by amplification, and reduced audibility in contexts of noise and reverberation. Delayed fricative use may have implications for morphological development. Atypically slow rates of change in syllable development may indicate that a child is at risk for delayed speech development.

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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.

A two-part study examined recognition of speech produced in quiet and in noise by normal hearing adults. In Part I 5 women produced 50 sentences consisting of an ambiguous carrier phrase followed by a unique target word. These sentences were spoken in three environments: quiet, wide band noise (WBN), and meaningful multi-talker babble (MMB). The WBN and MMB competitors were presented through insert earphones at 80 dB SPL. For each talker, the mean vocal level, long-term average speech spectra, and mean word duration were calculated for the 50 target words produced in each speaking environment. Compared to quiet, the vocal levels produced in WBN and MMB increased an average of 14.5 dB. The increase in vocal level was characterized by increased spectral energy in the high frequencies. Word duration also increased an average of 77 ms in WBN and MMB relative to the quiet condition. In Part II, the sentences produced by one of the 5 talkers were presented to 30 adults in the presence of multi-talker babble under two conditions. Recognition was evaluated for each condition. In the first condition, the sentences produced in quiet and in noise were presented at equal signal-to-noise ratios (SNR(E)). This served to remove the vocal level differences between the speech samples. In the second condition, the vocal level differences were preserved (SNR(P)). For the SNR(E) condition, recognition of the speech produced in WBN and MMB was on average 15% higher than that for the speech produced in quiet. For the SNR(P) condition, recognition increased an average of 69% for these same speech samples relative to speech produced in quiet. In general, correlational analyses failed to show a direct relation between the acoustic properties measured in Part I and the recognition measures in Part II.