A parametric method of computing acoustic characteristics of simplified three-dimensional vocal-tract model with wall impedance

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.

Effects of higher order propagation modes in vocal tract like geometries

“…This theory has been developed by several authors including Roure (1976), Kergomard et al (1989), Pagneux et al (1996), and Kemp (2002). It has already been applied to the vocal tract case with rectangular cross-sections by Motoki et al (2000). The aforementioned works are extended to consider straight vocal tract geometries with arbitrary cross-sections and eccentric junctions.…”

Influence of the Lip Horn on Acoustic Pressure Distribution Pattern of Sibilant /s/

“…It is described as being produced by turbulent jet flowi mpinging on the upper and lower teeth [5], whereby the lips are also thought to play arole [6]. High-frequencysound propagation is governed not only by aplane-waveacoustic mode, butalso by additional three-dimensional higher order modes, which contribute to both the acoustic field inside the vocal tract and the pressure pattern outside the vocal tract [7,8]. Therefore, the acoustic field outside the vocal tract depends not only on the area function of the vocal tract, butalso on the details of its three-dimensional geometry.…”

“…Therefore, in the current study,weexperimentally study the potential effect of the lip horn on the pressure distribution outside the vocal tract of sibilant fricative /s/ using a vocal tract replica, whose lips can be removedf rom the upper and lower jaws without changing the position of the jaws. Since some previous studies on vocal tract models have used the replica without lips (e.g., for vowels [9], for fricatives [7]), we compare results of the replica with and without lips. In addition, using areplica instead of ahuman speaker allows measurement of the spatial pressure pattern in the near field with ahigher spatial accuracythan the angle 15 • [3].…”

“…In addition, using areplica instead of ahuman speaker allows measurement of the spatial pressure pattern in the near field with ahigher spatial accuracythan the angle 15 • [3]. Indeed ahigher spatial accuracyismotivated since higher order modes associated with higher frequencies [7,8] potentially result in asignificant variation of the pressure pattern overasmall spatial interval [10].…”

Finite element analysis of fine-structural effect on acoustic characteristics of vocal tract

“…The simulation is carried out in a driving frequency range of 10 Hz to 5 kHz at intervals of 10 Hz and at intervals of 1 Hz in the vicinity of poles and zeros. The VTTFs defined in [5] are computed using the simulation results. …”