A discussion on the mechanism of sound absorption measurement method based on the ensemble averaging technique

Various kinds of measurement methods for sound absorption characteristics of materials have been proposed for several decades. Recently, some of the authors presented a method utilizing the ensemble averaging technique, namely EA method for short. In this paper, a detailed discussion is presented on measurement mechanism of the EA method based on the authors' former experimental results. The measurements were conducted in three reverberation rooms at different places as well as in situ conditions in a room of a dwelling house, in a corridor of a university building, in a university cafeteria, and at a terrace of a university building which is half-outside. Measured sound absorption coefficients agree well each other in the frequency range from 200 Hz to 3000 Hz. Assuming the Ergodicity of the system, robust results can be expected and the results support the assumption.