Acoustic variations in adductor spasmodic dysphonia as a function of speech task.

Acoustic phonatory events were identified in 14 women diagnosed with ADSD and compared to those of 14 women age-matched (+/-2 years) with no evidence of vocal pathology/dysfunction. The three acoustic parameters examined during sustained vowel production and reading included phonatory breaks, aperiodicity, and frequency shifts. Intra- and intermeasurer correlations showed high reliability for the measures. Findings indicated that those with ADSD produced a greater frequency of aberrant acoustic events than the controls during both tasks. For the group with ADSD, the amount and type of each event also varied with utterance type. The sustained vowel sample produced by those with ADSD consisted of a greater percentage of aperiodic segments followed by phonatory breaks and frequency shifts. During reading, frequency shifts were the predominant acoustic event, followed by phonatory breaks and aperiodicity. The advantage of segmenting the acoustic waveform into these measures and the relevancy of examining intertask performances by those with ADSD is discussed.