Further improvements of the measurement method for sound absorption characteristics using the ensemble averaging technique

In the authors' former papers, an in-situ measurement method using the ensemble averaging technique for sound absorption characteristics, surface normal impedance and absorption coefficient, was proposed and the method's reproducibility as well as the robustness have been examined. We call the method EA method, for short. In the EA method, two kinds of sensor types have been employed: one is two-microphone and the other is pressure-velocity sensor (PU sensor). Field measurements, however, frequently encounter difficulties due to practical complexities existing in/around the measurements, e.g. sensor-sensitivity-mismatching, material non-uniformity, etc. In this paper, a summary of the EA method is described, first. Next, detailed investigations on the sensor calibration procedure and statistical techniques are presented using an improved mathematical model for the EA method. Then, the outline of practical measurements conducted at several field environments including sports-arenas are given to discuss the model's plausibility.