The objective of the study was to investigate the influence of heat treatment on air-dried density, equilibrium moisture content (EMC), porosity, average surface roughness (Ra), sound transmission loss, and sound absorption coefficient of poplar (Populus nigra L.) and beech (Fagus orientalis Lipsky) woods. Specimens were exposed to four different temperature levels, namely 150 °C, 170 °C, 190 °C, and 210 °C, for 3 h. The sound absorption coefficient and sound transmission loss of test samples were determined in the frequency range of 63 Hz to 6300 Hz using an impedance tube. It was found that the density, EMC, and average surface roughness values of samples decreased with the heat treatment temperature. In contrast, as the heat treatment temperature increased, porosity of samples increased. The sound absorption coefficient and sound transmission loss of both wood species increased with the heat treatment temperature. The average sound absorption coefficients of untreated and heat-treated poplar samples were approximately 0.16 and 0.18; whereas for beech wood the corresponding values were approximately 0.15 and 0.16. The average sound transmission losses of untreated and treated poplar were approximately 22.7 and 24.0 dB, for the untreated and treated beech samples were 17.3 and 20.7 dB respectively.
Yeşil et al. (Mon,) studied this question.