LONG-TERM PHONATORY INSTABILITY IN INDIVIDUALS WITH MULTIPLE-SCLEROSIS

This paper uses a new approach to describe and quantify the long-term phonatory instability of speakers with MS. Sustained vowel phonations of 20 individuals with a definite diagnosis of multiple sclerosis (MS) and 20 age-and gender-matched individuals with normal speech were rec orded. The phonations were f(0) and intensity analyzed and subjected t o spectral analysis using the Fast Fourier Transform. Three methods fo r analyzing the instabilities are presented, compared, and related to perceptual judgments: (a) coefficients-of variation, (b) magnitude-bas ed analysis of spectral energy, and (c) frequency-based analysis of sp ectral components. All measures reliably distinguished between individ uals with MS and persons with normal speech. A single Factor based on a linear discriminant analysis of the frequency-based measures was esp ecially useful in distinguishing these groups. Critical frequency band s of instability corresponding to wow (1-2 HI), tremor (around 8 Hz), and flutter (17-18 Hz), distinguished the MS group from those of the c ontrol group.