This study will investigate some of the physiological properties of the larynx which are affected by different neurological disorders, and relate them to acoustic and perceptual measures of the sounds produced. The phonation of normal individuals and patients with Parkinson's disease, the ataxias, hyperkinetic movement disorders, unilateral superior nerve paralysis, unilateral recurrent nerve paralysis, and unilateral vagal nerve paralysis will be examined. The physiological properties to be investigated include laryngeal configuration as observed through fiberoptic techniques, glottal area and vocal fold contact area as provided by glottography, and aerodynamic measures of glottal air flow and estimated sub-glottal air pressure. The acoustic analyses include measures of period-to-period perturbation in duration and amplitude (jitter and shimmer), spectral balance such as the energy in the first formant compared to that in the fundamental, and measures of signal vs. noise. Perceptual measures involve the rating of harshness, breathiness, strained quality, and instability. The major goals of this project include a detailed description of vocal dysfunction associated with various types of neurological impairment, the understanding of the interrelationship of the measurement techniques employed, and the assessment of these techniques for their clinical application in the diagnosis of neurogenic voice disorders. The data will also be helpful in the understanding of the normal neuromotor organization of laryngeal function during voice production.