Three-dimensional acoustic field in vocal-tract.

Motoki, Kunitoshi

doi:10.1250/ast.23.207

Cited by 33 publications

(31 citation statements)

References 15 publications

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“…This downward shift of the formant frequencies is in line with the observations reported by Motoki (2002) and also contradicts the analytical results obtained by Sondhi (1983) for bent rectangular tubes of constant cross-section, which presented some upward shifts compared to straight configurations. The differences in wavefront curvature between straight and bent vocal tracts may be a possible explanation for the observed deviations.…”

Section: Effects Of Bending With Different Cross-sectional Shapessupporting

confidence: 67%

Influence of vocal tract geometry simplifications on the numerical simulation of vowel sounds

Arnela

Dabbaghchian

Blandin

et al. 2016

The Journal of the Acoustical Society of America

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For many years, the vocal tract shape has been approximated by one-dimensional (1D) area functions to study the production of voice. More recently, 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 about 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 these values 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.

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Section: Effects Of Bending With Different Cross-sectional Shapessupporting

confidence: 67%

Influence of vocal tract geometry simplifications on the numerical simulation of vowel sounds

Arnela

Dabbaghchian

Blandin

et al. 2016

The Journal of the Acoustical Society of America

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“…Generating diphthongs requires solving the wave equation in a human vocal tract that evolves from the shape, say for instance of vowel /a/, to the shape of vowel /i/, thus producing the sound /ai/. It is to be noted that for the numerical generation of vowels and diphthongs the acoustic pressure is the variable of interest, so most works to date concerning the generation of vowels directly deal with the FEM solution of the irreducible wave equation [10,11,12,13,14], or with its time Fourier counterpart, the Helmholtz equation [15,16,17,18]. Occasionally, the wave equation in mixed form has also been solved [19].…”

Section: Introductionmentioning

confidence: 99%

A Stabilized Finite Element Method for the Mixed Wave Equation in an ALE Framework With Application to Diphthong Production

Guasch¹,

Arnela²,

Codina³

et al. 2016

Acta Acustica united with Acustica

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Working with the wave equation in mixed rather than irreducible form allows one to directly account for both, the acoustic pressure field and the acoustic particle velocity field. Indeed, this becomes the natural option in many problems, such as those involving waves propagating in moving domains, because the equations can easily be set in an arbitrary Lagrangian-Eulerian (ALE) frame of reference. Yet, when attempting a standard Galerkin finite element solution (FEM) for them, it turns out that an inf-sup compatibility constraint has to be satisfied, which prevents from using equal interpolations for the approximated acoustic pressure and velocity fields. In this work it is proposed to resort to a subgrid scale stabilization strategy to circumvent this condition and thus facilitate code implementation. As a possible application, we address the generation of diphthongs in voice production.

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“…Only some small discrepancies have been found for vowel [u] (see fourth formant), which might be reduced increasing the number of crosssections. As far as the high frequency content is concerned, larger differences are observed for all the vowels, as this frequency range is more sensitive to small variations in the vocal tract shape (see e.g., [19,28]). Again, these may be reduced by increasing the number of cross-sections.…”

Section: Vowels [A] [I] and [U]mentioning

confidence: 99%

A Semi-Polar Grid Strategy for the Three-Dimensional Finite Element Simulation of Vowel-Vowel Sequences

et al. 2017

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Three-dimensional computational acoustic models need very detailed 3D vocal tract geometries to generate high quality sounds. Static geometries can be obtained from Magnetic Resonance Imaging (MRI), but it is not currently possible to capture dynamic MRI-based geometries with sufficient spatial and time resolution. One possible solution consists in interpolating between static geometries, but this is a complex task. We instead propose herein to use a semi-polar grid to extract 2D cross-sections from the static 3D geometries, and then interpolate them to obtain the vocal tract dynamics. Other approaches such as the adaptive grid have also been explored. In this method, cross-sections are defined perpendicular to the vocal tract midline, as typically done in 1D to obtain the vocal tract area functions. However, intersections between adjacent crosssections may occur during the interpolation process, especially when the vocal tract midline quickly changes its orientation. In contrast, the semi-polar grid prevents these intersections because the plane orientations are fixed over time. Finite element simulations of static vowels are first conducted, showing that 3D acoustic wave propagation is not significantly altered when the semi-polar grid is used instead of the adaptive grid. The vowel-vowel sequence [Ai] is finally simulated to demonstrate the method.

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Three-dimensional acoustic field in vocal-tract.

Cited by 33 publications

References 15 publications

Influence of vocal tract geometry simplifications on the numerical simulation of vowel sounds

Influence of vocal tract geometry simplifications on the numerical simulation of vowel sounds

A Stabilized Finite Element Method for the Mixed Wave Equation in an ALE Framework With Application to Diphthong Production

A Semi-Polar Grid Strategy for the Three-Dimensional Finite Element Simulation of Vowel-Vowel Sequences

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