On Self-oscillating Models of the Vocal Cords and its Computer Simulation

Abstract

This paper discusses models of the vocal cords, which can be categorized into a driving-point impedance (or terminal) type and a multi-mass system type. The former typically involves a so-called one-mass model and also a two-mass model of the vocal cords, and the latter represents the difference approximation of motion equations and also the finite element method. Models for the air flow through the larynx are also considered in connection with the models of the vocal cords. The mechanism of self-excited oscillation of the vocal cords is described in terms of the degeneration of natural modes of vibration which results from the glottal flow. The intention is to clarify the distinction between the self-excited oscillation and the free oscillation of the vocal cords. A self-excited oscillator inherently involves some of non-linear factors with respects to the amplitude of oscillation. In the vocal-cord oscillator, they are the collision of the bilateral vocal cords, the non-linear elasticity of cord tissue, and the non-linearity in the aerodynamics. These non-linear factors must properly be involved in the computer models of the vocal cords. Finally, general cosiderations of the computer simulation of cord-vibration are discussed. © 1981, The Japan Society of Logopedics and Phoniatrics. All rights reserved.