Tremor is a disturbance of normal control and feedback coordination of muscle tone, and results in rhythmic perturbation of the structures attached to the involved muscle groups. Since tremor disorders are not well defined with regard to the laryngeal muscles, this project will first, describe how tremor disorders differentially impact on respiratory flow, the vibratory characteristics of the vocal folds, and the pharyngeal outflow tract, during phonation. Secondly, the studies will examine how different types of perturbations affect objective measures of voice and vocal fold vibration. Patients with vocal tremor will be examined in detail and will have recording of multiple objective measures of phonation. Analysis of the data will correlate the movement of particular parts of the vocal tract with the effects on recorded objective measures. The data will be analyzed in conjunction with data from controlled experiments in an excised larynx model in which particular parts of the phonatory mechanism are perturbed ina known controlled manner. The hypothesis for these studies is that perturbation of respiratory drive, of the glottic aperture, and of the outflow vocal tract have specific different effects on the flow and acoustic signals during phonation, and the appropriate objective measures can differentiate among varied sites of phonatory disturbance. The long term goal of these studies is better diagnosis and better understanding of the pathophysiology of vocal tremors.