Applicability of the in situ measurement method using the ensemble averaging technique for sound absorption characteristics of materials with various absorption types

The ensemble averaging is one of the most important concepts for scientific theories as well as practical measurements especially for sound absorption measurements of materials. Applying a technique based on the ensemble averaging, the authors have been developing an in situ measurement method for sound absorption characteristics, surface normal impedance and absorption coefficient; and we call it EA-method, for short. The primary objective of our study was set to measure various building materials' sound absorption characteristics used in room acoustics simulations, especially in wave-based numerical methods. In the successive studies, EA-method showed excellent robustness as well as good reproducibility regardless of measurement places or material types. Herein, further applicability of the EA-method is discussed referring to measurement results of materials conducted at various environments. The measured materials are not only porous-types but also panel-types and resonant-types.