An acoustic investigation of Parkinsonian speech in linguistic and emotional contexts

The speech prosody of a group of patients in the early stages of Parkinson's disease (PD) was compared to that of a group of healthy age- and education-matched controls to quantify possible acoustic changes in speech production secondary to PD. Both groups produced standardized speech samples across a number of prosody conditions: phonemic stress, contrastive stress, and emotional prosody. The amplitude, fundamental frequency, and duration of all tokens were measured. PD speakers produced speech that was of lower amplitude than the tokens of healthy speakers in many conditions across all production tasks. Fundamental frequency distinguished the two speaker groups for contrastive stress and emotional prosody production, and duration differentiated the groups for phonemic stress production. It was concluded that motor impairments in PD lead to adverse and varied acoustic changes which affect a number of prosodic contrasts in speech and that these alterations appear to occur in earlier stages of disease progression than is often presumed by many investigators.