Voice characteristics in the progression of Parkinson's disease

This study examined the acoustic and perceptual voice characteristics of pa tients with Parkinson's disease according to disease severity. The perceptu al and acoustic voice characteristics of 30 patients with early stage PD an d 30 patients with later stage PD were compared with data from 30 normal co ntrol subjects. Voice recordings consisted of prolongation of the vowel /a/ scale singing, and a 1-min monologue. In comparison with controls and prev iously published normative data, both early and later stage PD patients' vo ices were characterized perceptually by limited pitch and loudness variabil ity, breathiness, harshness and reduced loudness. High modal pitch levels a lso characterized the voices of males in both early and later stages of PD. Acoustically, the voices of both groups of PD patients demonstrated lower mean intensity levels and reduced maximum phonational frequency ranges in c omparison with normative data. Although less clear, the present data also s uggested that the PD patients' voices were characterized by excess jitter, a high-speaking fundamental frequency for males and a reduced fundamental f requency variability for females. While several of these voice features did not appear to deteriorate with disease progression (i.e. harshness, high m odal pitch and speaking fundamental frequency in males, fundamental frequen cy variability in females, low intensity and jitter), breathiness, monopitc h and monoloudness, low loudness and reduced maximum phonational frequency range were all worse in the later stages of PD. Tremor was the sole voice f eature which was associated only with later stage PD.