Studies of the relationship between sound absorption coefficient and air permeability of wood

The longitudinal sound absorption capability and air permeability of three species of Japanese wood were investigated. The air permeability values of Sugi, Chanchin-modoki, and Yurinoki were 0.5, 0.06, and 0 (air flow not detected) darcy for the heartwood and 18.2, 0.92, and 0.91 darcy for the sapwood, respectively. The noise reduction coefficients of those three species were 0.04, 0.04, and 0.09 for the heartwood and 0.11, 0.05, and 0.14 for the sapwood, respectively. The mean sound absorption coefficients of those sample specimens in the frequency range of 50-6400 Hz were 0.08, 0.06, and 0.20 for the heartwood and 0.16, 0.09, and 0.30 for the sapwood, respectively. The sound absorption capability of the sample specimens increased with increase in air permeability.