Circuit Theory Based on New Concepts and Its Application to Quantum Theory 24. Application of Multiwire Transmission-Line Theory to the Analysis of Acoustic Characteristics of Vocal Tracts

The acoustic characteristics of a simplified three-dimensional vocal-tract model can be calculated using the multiwire transmission line theory. The acoustic field is represented in terms of both plane waves and higher-order modes in the vocal-tract model. This model is constructed using an asymmetrically connected structure of rectangular acoustic tubes to approximate a real vocal tract and can parametrically represent acoustic characteristics at higher frequencies where the assumption of plane wave propagation does not hold. Equivalent electrical transmission lines are introduced both for the propagative modes and evanescent modes in order to represent the localized distribution of sound pressure. The computational results show that additional peaks and valleys in the vocal-tract transfer functions can appear even for the case without any branch in the vocal tract. It is also shown that the visualization of the acoustic field is useful for understanding the phenomena of wave propagation in the vocal tract.