ENSEMBLE AVERAGED ABSORPTION CHARACTERISTICS OF MATERIALS USING AN IN-SITU TECHNIQUE : A BASIC APPLICATION ON HELMHOLTZ RESONATOR

摘要

An in-situ measurement method based on ensemble averaged surface normal impedance using pp and pu-sensors has been proposed by some of authors. In this paper, we aim to extend the applicability of the method into two types of Helmholtz resonator i.e. PET bottles and a self-made unit resonator. At first, the absorption coefficients of the PET bottles obtained by proposed method are compared with those of the reverberation room method, while the absorption characteristics of the resonator are compared with those of the method proposed by Iwase. Next, the effects of measuring absorption coefficients at different receiving points are examined. Comparisons show good agreements, indicating the possibility to apply the proposed method for resonance-type sound absorption materials.