Acoustic evidence for remapping of prosodic control in severe dysarthria
By R. Patel
Eight speakers with severe dysarthria produced a set of three-syllable phrases as both questions and statements. We were interested in understanding whether speakers with severe dysarthria could mark this contrast despite reduced flexibility and control of their speech production mechanism and if so, what parameters they used to signal the difference. Acoustic analysis of the dysarthric utterances revealed consistent differences in average F0, slope of F0, and duration between questions and statements. Average F0 for all syllables was higher for questions compared to statements and especially so for the final syllable. The slope of the final syllable was rising as expected from normal speech. However, dysarthric speakers also produced falling F0 contours for statements to further differentiate them from questions. In addition, speakers lengthened the final syllable for questions, a cue that has not conventionally been associated with the question-statement contrast in English. The patterns of F0 and duration control evidenced here may signal remapping of prosodic control onto features that are easier for speakers with dysarthria to control as well as strategies that exaggerate prosodic contrasts in light of narrowed vocal range and flexibility.