Absorption modeling with ensemble averaged impedance for wave-based room acoustics simulations

With the rapid progress of computers, wave-based room acoustics simulations like finite element method have come to be applicable onto many practical problems on acoustics. Generally, such methods can calculate sound fields quite accurately provided their boundary modelings are given appropriately. Although the absorption on the boundary can be modeled efficiently by using surface impedance, the impedance database is not accumulated yet. It is due to the difficulty in the practical measurement of surface impedance of materials at field conditions. To overcome the difficulty, the authors proposed a way to measure surface impedance by using ensemble averaging technique. In this paper, the basic concept of the authors’ measurement method of surface impedance is summarized first. Then, an application of the measurement technique onto a realistic sound field in a cafe-restaurant is shown, and comparisons with the other methods are given to prove the effectiveness of the technique.