Sound Absorption Measurement Method using Ensemble Averaging Technique: A Robust Method for Surface Impedance Including in-situ Applications
* Presenting author
Sound absorption characteristics of materials are of importance for controlling the quality of sound fields as well as of materials. In our previous paper, we proposed the concept and measurement method for surface normal impedance and sound absorption coefficient at random incidence condition, namely, ensemble averaged surface normal impedance and sound absorption coefficient. We named the measurement method as EA method, for short. We also showed the theoretical validation using the boundary element method and experimental confirmations on the effectiveness of EA method in successive several papers. In this paper, the outline of EA method is summarized, first. Then, reproducibility of the results are examined on measurements conducted both in reverberation rooms and in-situ. All the measurements were conducted by EA method with a pressure-velocity sensor (Microflown PU-sensor) which was calibrated on site in an acoustic tube. In-situ measurements were conducted at office room, living room, cafeteria and outside terrace. The results reveal that rather robust absorption coefficient values with the uncertainties less than 0.04 ~ 0.05 are obtained regardless of measurement places and that EA method has broad adaptability to sound absorption measurements at various conditions.