Influence of vocal tract geometry simplifications on the numerical simulation of vowel sounds
Résumé
For many years the vocal tract shape has been approximated by one-dimensional (1D) area
functions to study the production of voice. More recently three-dimensional (3D) approaches
allow one to deal with the complex 3D vocal tract, although area-based 3D geometries of
circular cross-section are still in use. However, little is known on the influence of performing
such a simplification, and some alternatives may exist between these two extreme options. To
this aim, several vocal tract geometry simplifications for vowels [A], [i] and [u] are investigated
in this work. Six cases are considered, consisting of realistic, elliptical and circular cross-
sections interpolated through a bent or straight midline. For frequencies below 4−5 kHz, the
influence of bending and cross-sectional shape has been found weak, while above that value
simplified bent vocal tracts with realistic cross-sections are necessary to correctly emulate
higher-order mode propagation. To perform this study the Finite Element Method (FEM)
has been used. FEM results have also been compared to a 3D multimodal method and to a
classical 1D frequency domain model.