Numerical analysis and physical consideration of vocal fold vibration by modal analysis

Vocal fold vibration is self-excited vibration due to the interaction between the vocal folds and expired air. To analyze vocal fold vibration, several models comprising masses and springs have been proposed to date, but with those models it is difficult to determine parameter values and calculate the phenomenon in detail. Also, several researchers have analyzed vocal fold vibration using the finite element method (FEM) and the finite volume method, but such large-degree-of-freedom analyses incur high computational cost. To solve these problems, we propose a vocal fold vibration analysis model based on modal analysis. The natural modes of the vocal folds are obtained by FEM, and the air is simulated by a one-dimensional model based on Bernoulli's equation. In this approach, because the natural modes are obtained by FEM, parameters based on actual physical properties (Young's modulus, etc.) can be used, and the calculation cost is relatively low because of the modal and one-dimensional fluid analyses. To validate the proposed model, its results are compared with those from experiments on silicone vocal folds and simulations using ANSYS software, and the results correspond. Furthermore, the necessary conditions for the vocal folds to enter two particular modes of self-excited vibration are derived mathematically, and those two modes are confirmed to be dominant in the periodic solution region.