In-situ sound absorption measurement method of materials using ensemble averaging-Comparison of proposed method with tube method or reverberation room method

The sound absorption characteristics of building materials are generally measured by the reverberation room method and the impedance tube method, however, measurement values by these methods are known to have uncertainties due to the diffuseness of sound fields and the installation condition of materials to the tube, respectively. On the other hands, the authors have recently proposed the sound absorption measurement method using ensemble averaging technique, i.e., EA method. The method yields a simple and efficient in-situ measurement of surface normal impedance of materials at random-incidence. The purpose of this study is to show the relationship between the EA method and conventional methods: the reverberation room method and the impedance tube method. In this paper, the sound absorption characteristics of four materials: rook-wool board, gypsum board, carpet tile and needle felt are measured by the three method, and the sound absorption coefficient of EA method is compared with those of the reverberation room method and the impedance tube method.