Modifications in aerodynamic variables by persons who stutter under fluency-evoking conditions

The purposes of this study were to (a) compare the effects of fluency-evoking conditions on aerodynamic variables in 10 persons who stutter with those previously reported for 12 individuals who do not stutter; (b) determine if any changes demonstrated in the amplitude and/or timing of aerodynamic variables were accounted for by changes in speech intensity; and (c) determine if any amplitude or timing changes in flow and intraoral pressure were related to improved fluency. The fluency-evoking conditions were choral reading (CR), metronome-pacing (MET), delayed auditory feedback (DAF), and noise (NOISE). From 8 words beginning with plosive consonants in CVC contexts read aloud in sentences, measures were made of 8 variables, including closure duration, amplitude and time to maximum airflow and intraoral pressure for initial plosives, and the duration and intensity of the following vowel. Speech rate was also computed. Only fluently produced target words from persons who stutter were analyzed. All persons who stutter showed improved fluency under all conditions. Both groups demonstrated significant (p < or = 0.006) condition effects for peak flow, vowel intensity, and pressure rise time. Thus, fluency-evoking conditions affected these variables regardless of speaker type. Both groups changed peak pressure in similar directions from baseline depending on condition, but not significantly for each group in the same conditions. Persons who stutter significantly increased speech rate for CR, DAF, and NOISE; and persons who do not stutter significantly decreased rate under DAF. The reported changes in peak pressure and peak flow could not be accounted for by changes in vowel intensity. Larger improvements in fluency occurred under conditions when peak flow and peak pressure values were decreased from baseline. Thus, variables that were modified by both groups when speaking under conditions were also the variables related to changes in fluency for the persons who stutter.