Voice Onset Time for the Word-Initial Voiceless Consonant /t/ in Japanese Spasmodic Dysphonia-A Comparison With Normal Controls.

Objectives: Voice onset time (VOT) for word-initial voiceless consonants in adductor spasmodic dysphonia (ADSD) and abductor spasmodic dysphonia (ABSD) patients were measured to determine (1) which acoustic measures differed from the controls and (2) whether acoustic measures were related to the pause or silence between the test word and the preceding word.

Methods: Forty-eight patients with ADSD and nine patients with ABSD, as well as 20 matched normal controls read a story in which the word "taiyo" (the sun) was repeated three times, each differentiated by the position of the word in the sentence. The target of measurement was the VOT for the word-initial voiceless consonant /t/.

Results: When the target syllable appeared in a sentence following a comma, or at the beginning of a sentence following a period, the ABSD patients' VOTs were significantly longer than those of the ADSD patients and controls. Abnormal prolongation of the VOTs was related to the pause or silence between the test word and the preceding word.

Conclusions: VOTs in spasmodic dysphonia (SD) may vary according to the SD subtype or speaking conditions. VOT measurement was suggested to be a useful method for quantifying voice symptoms in SD.