1999 年 20 巻 6 号 p. 433-438
Brick/block absorbing walls with openings backed with porous materials are often used for sound absorptive treatments in buildings. This type of brick/block walls have a frequencyselective sound absorption at low frequencies, which is usually explained as the Helmholtz resonance. In addition, they often have peaks of sound absorption at frequencies much different from the Helmholtz resonance frequency. In this paper, the sound absorption mechanism of this type of walls was investigated by experiments. As a result, it has been confirmed that the sound absorption is caused by the effect of open-pipe resonance which happens in the openings. In the case of brick/block sound absorptive constructions made of materials with a thickness of about 10 cm, sound absorption caused by the open-pipe resonance is considerably significant at high frequencies. Therefore, when this type of sound absorption construction is used for room acoustic treatment, sound absorption at high frequencies must be carefully considered in acoustical design.