Acoustic analysis of stutterers' fluent speech before and after therapy.

The speech of 14 stutterers was analyzed prior to and at the termination of a 5-week stuttering therapy program to examine the relationship between nine selected acoustic variables and stuttering frequency. Group analyses indicated that pre- to post-therapy changes in stuttering frequency were accompanied by mean changes in five of the nine acoustic variables, a finding which is consistent with previous literature. Correlational analyses indicated that only silence in the voiced stop consonant intervocalic interval (IVI) was significantly correlated with stuttering frequency prior to therapy (i.e., lower stuttering frequency values were associated with shorter durations of silence during the IVI). Furthermore, the degree of reduction in silence was positively correlated with the magnitude of reduction in stuttering frequency due to therapy. These findings suggest that silence in the IVI may reflect the operational status of some mechanism which may underlie disfluent speech.