Speech production by a vocal cords-vocal tract-vocal tract wall vibration model

Abstract

This research was aimed at finding the effects of finitehess in the mechanical impedance of the vocal organs on speech sounds. A speech synthesis program has been developed considering the vocal tract wall vibration that causes sound leakage from the vocal cavity to the nasal cavity even when the velum is closed. The radiation of sound from the outer surface of the vocal tract is not always negligibly small, and its effect is enhanced by the nasal cavity. The synthesis program has the parameters of the physical properties and pressure of ambient gases, as well as the mechanical impedance of a yielding vocal tract wall. The wall vibration is treated as a small perturbation in the area function of the vocal tract. The following items will be discussed in the paper: comparisons between vowels with and without vocal tract wall vibration, sounds from the mouth opening, nostrils, and vocal tract wall, and the distribution of the strength of the wall vibration along the vocal tract. The effect of the pressure of ambient gases on these items will also be discussed.