Fundamental Experiments on Evaluating the Sound Absorption Coefficient of Porous Concrete

Abstract

This study examined the sound absorption performance of porous concrete used as an exterior wall cladding material, focusing on four factors: porosity, particle size of aggregate, surface texture, and moisture content. In addition, the influence of measurement techniques was investigated by comparing sound absorption coefficients obtained using the oblique incidence method with those measured by the diffuse incidence method specified in JIS A 1409 (reverberation room method). The oblique incidence method is a simple laboratory-scale technique that does not require a large reverberation room or specialized facilities and uses only limited measuring equipment. Although the sound absorption coefficients obtained by this method were lower than those measured by the diffuse incidence method, the results were stable, particularly in the high-frequency range above 2500 Hz. Therefore, the oblique incidence method is considered suitable for comparative evaluation of material and mix design parameters. The results showed that increasing porosity led to higher sound absorption coefficients at frequencies above 3000 Hz. In contrast, the particle size of aggregate had no clear effect on sound absorption. Furthermore, the sound absorption coefficients tended to be higher in wet conditions than in dry conditions.