Change in Sound Absorption Capability on Thermally Modified Transverse and Radial Planes of Indonesian Homalium foetidum

This study investigated the difference in sound-absorbing capabilities by thermally modified wood with respect to temperature and anatomical direction. Indonesian Homalium foetidum was used as testing material. After the samples were thermally modified at 170, 200, and 230 °C for 8 h, sound absorbing capability in the transverse and radial planes was investigated. As the treatment temperature was increased, the noise reduction coefficient (NRC) of the radial plane increased by 26.4%, and that of the transverse section increased by 7.3%. However, at 230 °C, the maximum NRC of the radial plane was 0.097 (SD: 0.015), and that of the transverse section was 0.263 (SD: 0.016). As a consequence, the sound absorption effect of the radial plane was negligible. Therefore, thermally modified Indonesian Homalium foetidum could be expected to absorb sound when used as a transverse section.