Acoustic and perceptual analysis of word-initial stop consonants in phonologically disordered children.

Spectrographic measures of voice onset time (VOT) were made for phonologically disordered children in whom a voicing contrast was just beginning to emerge. These temporal measures were related to adult listeners' perception of voicing of the initial stop consonant to determine how well VOT could predict perceived voicing. In general, the predictive utility of VOT was not very high. The relation between VOT as produced by the phonologically disordered children and perceived voicing ranged from 0.31 to 0.43. A finer-grained analysis was conducted to determine what other acoustic cues might have influenced the listeners' judgments of voicing. Although no one acoustic cue could be found to explain all listeners' responses, spectral cues such as fundamental and F1 frequencies at the onset of voicing, as well as the burst and aspiration amplitude relative to the vowel onset amplitude accounted for the perceived voicing of about half of the tokens that were not differentiated by VOT. Rather than relying solely on the temporal characteristics of the VOT interval, a matrix of acoustic cues may influence how a listener perceives word-initial voicing as produced by phonologically disordered children.