Vocal tract acoustics using the transmission line matrix (TLM) method

Abstract

Most traditional theories of speech production are currently based on plane waves and on one-dimensional analysis. It i s however well-known that when the frequency of sound reaches a cut-on frequency, higher acoustical modes start to propagate and can become predominant. It is therefore important t o evaluate the effects of these higher modes, especially in order t o improve acoustical models of the vocal tract. This paper describes a new numerical method to study the propagation and the radiation of speech sounds, and to compute acoustic characteristics of the vocal tract. This method, named Transmission Line Matrix or Modelling (TLM), has been used for simulating electromagnetic wave propagation and is used here for the first time in acoustics. The TLM method provides time domain solutions in 2D and 3D spaces. The main advantage of this method is the simplicity of formulation and programming for a large range of applications. We first describe the principle on which the TLM method is based. The method as well as the boundary conditions used are validated using classical tests. A systematic study of higher order mode propagation and radiation is then presented. We focus on the influence of some critical parameters such as vocal tract width and location of the sound source. In particular, we show how, using TLM simulation, it is possible to derive modal reflection and transmission characteristics of the vocal tract. A typical example of simulation is presented and discussed.

Modal Locking Between Vocal Fold Oscillations and Vocal Tract Acoustics

“…Some of the most popular approaches to modelling phonation are based on the Kelly-Lochbaum VT [20] or various transmission line analogues [21,22,23].…”

Modeling Thermal Radiation Effects in Nanowires Using the TLM Method

“…The TLM method was originally established to solve Maxwell's equations [16]. It has been applied to the modeling of many physical phenomena, for instance, charge diffusion in semiconductor devices, laser diodes, and vocal tract acoustics [17][18][19]. The unconditional stability and the precise nature of TLM are significant strengths of this method.…”

“…At this stage the reflection and the transmission coefficients come into play, where these pulses either get transmitted or reflected. Generally, heat diffusion problems are addressed in a wide range of applications, such as semiconductor lasers, power semiconductor devices, and optoelectronics [16,18,[22][23][24][25][26][27]. Recently, the TLM method was used in [28] to solve the problem of transient heat transfer in inhomogeneous Thermal radiation using TLM method 3 arrangements of interconnects and dielectrics.…”

Investigation of the Effect of Obstacle Placed Near the Human Glottis on the Resultant Sound Pressure

“…FEM based simulation of human vocal tract are done by many researchers [10][11]. In this research paper Fant's model of human vocal tract is adapted to simulate the human vocal tract using FEM, in order to investigate the effect of obstacle near the glottis on the sound pressure in human vocal tract.…”