Acoustic Characteristics of Fricatives /s/ and /∫/ Produced by Speakers with Parkinson’s Disease

PURPOSE: This study investigated acoustic characteristics of fricatives produced in a repeated syllables task by speakers with Parkinson’s disease (PD), focusing on temporal, intensity, and spectral moment analyses. METHODS: Ten participants with PD and nine neurologically-healthy participants were asked to repeat the two words, sigh and shy, ten times in a row and at a comfortable rate. Acoustic measurements were made for duration and intensity of each fricative and vowel, plus four coefficients of spectral moments for the fricatives. RESULTS: Results indicated a varying effect of duration difference between group, with marginally shorter duration of fricatives but much shorter duration of vowels in speakers with PD, as compared to controls; comparable vowel-fricative intensity differences for the two groups; and for the group with PD relatively intact coarticulation throughout fricative. CONCLUSIONS: The findings suggest considering the complex effect of overall speech rate on different kinds of segments in PD. The findings also have implications for speech stimuli in research on coarticulation.