Abstract
The variability and controllability of vocal fundamental frequency (F0) are investigated by analyzing the acoustic and perceptual characteristics of sustained vowel samples recorded from patients with spasmodic dysphonia (SPD) as well as patients with various types of laryngeal disorders and normal controls. All the pathological groups show larger variations in F0 or lower controllability than the normal controls. The voice segments perceptually judged as non-sporadic show significantly larger variations in F0 than the normal controls. From the voice segments perceptually judged as sporadic, instantaneous changes in F0 or in amplitude, chaotic changes in voice waveform such as bifurcations are observed. Based on the obtained results, a model of normal and disordered voice control mechanism is proposed, in which morphological and neural abnormalities affect voice variability. The acoustic analysis method described here is found beneficial in analyzing voice variability and controllability, and can provide useful information to know normal and disordered voice control mechanisms.
