Rick M. Roark
Dept. of Otolaryngol., New York Medical College, Munger 170, Valhalla, NY 10595
Eric M. Dowling Ronald D. DeGroat
Univ. of Texas, Dallas, TX
Ben C. Watson Steven D. Schaefer
New York Medical College, Valhalla, NY
Time-synchronous digital recordings of thyroarytenoid (TA) myoelectric activity (via percutaneous hooked-wire electrodes) were obtained for 10 normal control and 11 spasmodic dysphonia subjects during performance of five vocal tract tasks of increasing motoric complexity: (1) quiet breathing, (2) Valsalva maneuver, (3) whispered |i|, (4) voiced |i|, and (5) Beep beep went the heap. Three-dimensional power spectral density functions, PSD(f,t), were determined for a selected segment of the signals, and measures of median frequency, mean frequency, bandwidth, and center frequency of PSD(f,t) were derived for each sample point. Statistical median, mean, standard deviation, maximum, minimum, and mode of the PSD measures were computed to compose feature vectors for each signal. Discriminate analysis and maximum likelihood classification tests were applied to obtain global discrimination measures for the two subject populations as a function of task performance. Results of the analysis are reported that reveal a task effect. Graphical presentations of TA myoelectric and speech acoustic signals with accompanying time--frequency PSD plots are given. Comparisons are made among incidents of spasm and nonspasm, posing questions into physiologic meaning and basis of spectral- versus amplitude-defined laryngeal muscle spasms. [Work supported by NIH Grant No. DC00410 and NSF Grant No. MIP9203296.]