Computation of the acoustic characteristics of simplified vocal-tract models by 3-D finite element method

The acoustic characteristics of vocal-tract models are investigated using a three-dimensional finite element method. Several finite element models are created in order to examine the influence of the simplification of the vocal-tract shapes on the finer acoustic characteristics up to the higher frequencies of around 8 kHz. The simplification takes into account the following aspects: cross-sectional shape, bend, branches of the pyriform fossa and the valleculla, and lip protrusion. The effects of the yielding vocal-tract wall are also studied. The results indicate that with the frequency range up to around the third formant, the simplification of the cross section and the bend is considered to be an effective approximation. It is shown that the use of soft walls suppresses the appearance of sharp peaks and zeros in the frequencies above 3 kHz. It is suggested that the lips and the branches independently affect the shifts of the first three formant frequencies.