The Effects of Modifying the
Fundamental Frequency Contour on Segmental
Level Speech Errors in Persons with Parkinson Disease
This study investigates the role of fundamental frequency (F0) variation on speech intelligibility measures for persons with dysarthria associated with idiopathic Parkinson disease. In speakers with intact articulation abilities, flattening the F0 contour has been shown to decrease intelligibility. For dysarthric speakers, very little is known about the relationship between F0 and speech intelligibility in speakers who have production difficulties. Reduced F0 variability across an utterance may reduce the salience of acoustic cues to segment identity. Similarly, modification of segmental elements, as a result of an inability to control the speech mechanism, may influence the perception of sound segments as well as the perception of the rhythmic structure of the utterance. The effects of both segmental and suprasegmental variables on speech intelligibility have been addressed independently, however, few studies have been directed toward studying the interaction of these variables and their effects on intelligibility. This study begins to address the nature of this interaction using a speech resynthesis program to modify F0 contours. It wais hypothesized that flattening of the F0 contour will increase segmental error rates, particularly vowels, and enhancing the F0 contour to include the peaks and valleys typical of normal speech will decrease segment error rates.