Perception of voiceless fricatives by normal-hearing and hearing-impaired children and adults

This study examined the perceptual-weighting strategies and performance-audibility functions of 11 moderately hearing-impaired (HI) children, 11 age-matched normal-hearing (NH) children, 11 moderately HI adults, and 11 NH adults. The purpose was to (a) determine the perceptual-weighting strategies of HI children relative to the other groups and (b) determine the audibility required by each group to achieve a criterion level of performance. Stimuli were 4 nonsense syllables (/us/, /u∫/, /uf/, and /uθ/). The vowel, transition, and fricative segments of each nonsense syllable were identified along the temporal domain, and each segment was amplified randomly within each syllable during presentation. Point-biserial correlation coefficients were calculated using the amplitude variation of each segment and the correct and incorrect responses for the corresponding syllable. Results showed that for /us/ and /u∫/, all four groups heavily weighted the fricative segments during perception, whereas the vowel and transition segments received little or no weight. For /uf/, relatively low weights were given to each segment by all four groups. For /uθ/, the NH children and adults weighted the transition segment more so than the vowel and fricative segments, whereas the HI children and adults weighted all three segments equally low. Performance-audibility functions of the fricative segments of /us/ and /u∫/ were constructed for each group. In general, maximum performance for each group was reached at lower audibility levels for /s/ than for /∫/ and steeper functions were observed for the HI groups relative to the NH groups. A decision theory approach was used to confirm the audibility required by each group to achieve a ≥ 90% level of performance. Results showed both hearing sensitivity and age effects. The HI listeners required lower levels of audibility than the NH listeners to achieve similar levels of performance. Likewise, the adult listeners required lower levels of audibility than the children, although this difference was more substantial for the NH listeners than for the HI listeners.