The accuracy of the analysis of a sound field in a room by numerical method such as the time-domain finite element method (TDFEM) depends not only on the time step and spatial discretization but also on the modeling method and accuracy of the boundary conditions of the room. In this study, the effect of normal acoustic impedance ratio on the decay of sound pressure and particle velocity in modeling sound-absorbing materials of the analysis using TDFEM is investigated by comparing with measurements. First, the decay curves of sound pressure level of a sound field in a rectangular room without absorbing materials obtained by TDFEM are compared with those obtained by measurements. Next, the sound field in the rectangular room with an absorbing material are analyzed by the TDFEM. Two types of normal acoustic impedance ratio are used to model the absorbing materials in the analysis: the impedance obtained by a measurement method for sound absorption characteristic based on ensemble averaging (zEA) and the impedance obtained by the tube method (zTube). It was shown that the decay of the particle velocity normal to the absorbing materials obtained by the analysis with zTube is corresponding to those of the measurement. On the other hand, the decay of the sound pressure levels obtained by the analysis with zEA is corresponding to those obtained by the measurement.
Tomiku et al. (Wed,) studied this question.