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.