Effect of time-scale modification of speech on the speech recognition threshold in noise for hearing-impaired and language-impaired children.

In this study, the effect of time-compression and expansion of speech on speech perception in noise was measured for a group of hearing-impaired and a group of language-impaired children relative to control groups of normal children and normal adults. The children's ages ranged from 9 to 12 years. For all time-scale modified conditions, both hearing-impaired and language-impaired children had significantly higher speech recognition thresholds in noise (SRTN) than their normal peers, who performed almost equally well as the adult control group. Time-expansion was shown to have a negligible effect on SRTN for all groups when compared to the control condition, i.e. 0% time-compression. The difference in SRTN between the control and the impaired groups was, in general, not significantly altered by the degree of time-compression or expansion of speech, although a clear trend towards greater differences for increasing time-compression was observed. Five tests of auditory discrimination and auditory memory were also administered to both groups of impaired children. In a step-wise multiple regression procedure, 94% of variation in SRTN in the control condition could be explained by the score on the ADIT C (type Wepman; discrimination task) and the maximum speech recognition score for monosyllables in quiet.