Contour tone production by Cantonese speakers with cerebral palsy
By V. Ciocca, T.L. Whitehill, and S.S. Ng
This study investigated the production of Cantonese contour tones by speakers with dysarthria and by control speakers with no known speech or language disorder. Nineteen Cantonese speaking adults with cerebral palsy were included in the dysarthric group. Speakers produced 11 monosyllabic words which contrasted among low-rising, high-rising, and low-falling tones. An acoustic analysis of the utterances was performed by measuring the fundamental frequency (f0) at five equally spaced time points within the voiced portion of each word. Speakers with dysarthria had higher f0 than control speakers. Unlike control speakers, speakers with dysarthria produced a decrease in f0 towards the end of the utterances for rising tones. Male, but not female, dysarthric speakers also had larger variability than control speakers. The following abnormal f0 patterns for individual utterances were observed: i) falling f0 contour for rising tones, or rising f0 contour for falling tones, ii) excessively large or small f0 range. These findings supplement previous acoustic measurements of the production of level tones, and support observations obtained through perceptual judgments.