Effects of head geometry simplifications on acoustic radiation of vowel sounds based on time-domain finite-element simulations

Abstract

One of the key effects to model in voice production is that of acoustic radiation of sound waves emanating from the mouth. The use of three-dimensional numerical simulations allows to naturally account for it, as well as to consider all geometrical head details, by extending the computational domain out of the vocal tract. Despite this advantage, many approximations to the head geometry are often performed for simplicity and impedance load models are still used as well to reduce the computational cost. In this work, the impact of some of these simplifications on radiation effects is examined for vowel production in the frequency range 0-10 kHz, by means of comparison with radiation from a realistic head. As a result, recommendations are given on their validity depending on whether high frequency energy (above 5 kHz) should be taken into account or not.

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

“…A suitable option to find the matrix of stabilization parameters τ is based on a Fourier analysis of the equation for the subscales (14). Let use a hat symbol to denote Fourier transformed functions.…”

“…Let use a hat symbol to denote Fourier transformed functions. Transforming (14) to the wave number domain allows us to bound the norm of the Fourier transformed residualR h as [4,32] …”

“…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].…”

Synthesis of VV Utterances from Muscle Activation to Sound with a 3D Model

“…Third, constructing the vocal tract 3D geometry is not as simple as calculating the area function in an articulatory model and especially not in a biomechanical model [12]. The first and second reasons are not valid anymore, since 3D articulatory biomechanical models [10,11] and acoustic models [13,14] are currently available. However, construction of a 3D vocal tract geometry, which is a requirement for the acoustic simulation, is still a challenge in particular when using articulatory models that include separate articulators.…”

A Unified Numerical Simulation of Vowel Production That Comprises Phonation and the Emitted Sound

“…An immersed boundary method is adopted in those works and contact is enforced by a kinematic constraint. With regard to VT acoustics, several works have been performed to date for static vowels sounds (see e.g., [6,7,8,9, 10]), and not long ago for dynamic vowel sounds as well [11].…”