Acoustic Wave Propagation Problems In Computational Acoustics With Application To Vocal Tract

Computational acoustic has been applied to many fields such as speech acoustic,aerodynamic acoustics,architectural acoustics and so on.Among them,the acoustic simulation for the static boundary is the most successful.However,the shape of the vocal tract always keeps changing in continuous speech production.There is no better way to deal with the problems of complex boundary and moving boundary.Therefore,taking into account these problems within the vocal tract is very important to make the simulation of human sound wave propagation more complete,accurate and real.Numerical simulation is an important way to study the acoustic problems.These numerical methods,including finite element method(FEM),boundary element method(BEM),and finite-difference time-domain(FDTD)method,have achieved great success in acoustic computation.Among others,FDTD plays a vital role due to its accuracy and high efficiency.However,it results in a difficult situation in the process of grid generation and transformation.In this paper,a new and efficient numerical model is proposed for simulating the acoustic wave propagation and scattering problems due to a complex geometry.Immersed boundary method(IBM)is an important method in the computational fluid dynamics.In this method,two different grid systems are employed.A regular Cartesian mesh is used to simulate the fluid dynamics,a Lagrangian representation is used for the boundary,and a force field is added to simulate the interaction between these two grids.In this model,the complex wall boundary is treated with the IBM,and then the governing equations are discretized by FDTD method to calculate the pressure and velocity alternatively.The developed model is verified in the case of acoustic scattering by a cylinder,for which the exact solutions exist.This model is then applied to sound wave propagation in a 2D vocal tract for vowel /a/ and vowel /o/.The numerical results have good agreements with solutions in literature.It is note that this model has potential to solve the moving boundary problems.