Abstract
The classic two-mass model of the vocal folds (Ishizaka and Flanagan, 1972) has been extended to a three mass model in order to more realistically represent the body-cover vocal fold structure (Hirano, 1974). The model consists of two cover masses coupled laterally to a body mass by nonlinear springs and viscous damping elements. The body mass, which represents muscle tissue, is further coupled laterally to a rigid wall (assumed to represent the thyroid cartilage) by a nonlinear spring and a damping element. The two cover springs are intended to represent the elastic properties of the epithelium and the lamina propria while the body spring simulates the tension produced by contraction of the thyroarytenoid muscle (TA). Additionally, the two cover masses are coupled to each other through a linear spring which can represent vertical mucosal wave propagation. Effects on the vocal fold movement due to changes in subglottal pressure, spring tensions, and vocal tract loading are shown.

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