Spectral properties of fricatives in Parkinson’s Disease

Abstract

Consonant imprecision is one of the most prominent speech characteristics of Parkinson’s Disease (PD). Few studies have characterized the nature of the imprecision for sound classes other than stop consonants, however. Research further suggests that consonant imprecision may improve with slowed speaking rate, perhaps as a result of increased articulatory displacements [M. P. Caliguiri, Brain Lang. 35, 493–502 (1989)]. In the current study, nine speakers with PD and nine age and gender matched neurologically healthy speakers read the Farm Passage at habitual and slow reading rates. Spectral moments were used to describe /s/ and /∫/ fricatives occurring in the word initial position of the reading passage. For both the habitual and slow rate conditions, moment coefficients for speakers with PD were compared to moment coefficients for the healthy speakers to characterize between group differences in fricative productions. Within each speaker group, moment coefficients for the habitual rate condition were compared to moment coefficients for the slow rate condition to evaluate the effects of slowed speaking rate on fricative productions.