Abstract
A method of computing the acoustic characteristics of a simplified three-dimensional vocal-tract model with wall impedance is presented. The acoustic field is represented in terms of both plane waves and higher order modes in tubes. This model is constructed using an asymmetrically connected structure of rectangular acoustic tubes, and can parametrically represent acoustic characteristics at higher frequencies where the assumption of plane wave propagation does not hold. The propagation constants of the higher order modes are calculated taking account of wall impedance. The resonance characteristics of the vocal-tract model are evaluated using the radiated acoustic power. Computational results show an increase in bandwidth and a small upward shift of peaks, particularly at lower frequencies, as already suggested by the one-dimensional model. It is also shown that the sharp peaks at higher frequencies are less sensitive to the values of wall impedance even though the attenuation of the higher order modes is larger than that of plane waves.
