Finite-difference time-domain method for heterogeneous orthotropic media with damping

Abstract

The finite-difference time-domain method, in which longitudinal and shear waves and two types of damping terms are considered, has been proposed as a prediction method for structure-borne sound, particularly architectural acoustics. In this method, it is assumed that both solids and fluids are governed by a unique set of motion equations and viscoelastic constitutive equations. Therefore, the method can be applied to heterogeneous media and vibroacoustic problems by employing averaged material parameters. However, the formulation is limited to isotropic media. Unfortunately wooden frames, which are common building materials, cannot be considered as isotropic media. Herein, a method of formulating heterogeneous orthotropic media is proposed. As an example, the propagation of waves in a wooden block and the radiated sound are calculated. The numerical results of both the time and frequency responses are compared with the measured ones. These investigations show that the calculated data does not correspond to the measured data if the wooden block is assumed to be isotropic. Moreover, the results calculated with orthotropy taken into account agree well with the measured one, but the material parameters must be identified using measured data.