Abstract
This study investigated changes in the sound absorption coefficients of three anatomical sections of cubed spruce (Picea sitchensis), Douglas fir (Pseudotsuga menziesii), and larch (Larix kaempferi) after microwave treatment. Microwave treatment at 1000 W and 2.4 GHz for 20 min increased the sound absorption coefficients (at 2000–5000 Hz) of spruce by 6.9% in the transverse section, 20.0% in the radial section, and 31.7% in the tangential section. The sound absorption coefficients of Douglas fir increased by 28.9% in the transverse section, 19.1% in the radial section, and 50.0% in the tangential section. Larch coefficients increased by 16.7% in the transverse section, 37.2% in the radial section, and 38.8% in the tangential section. The sound absorption coefficients of the softwoods differed according to species and anatomical plane after microwave treatment. It was concluded that changes in the measured sound absorption coefficient indicate alteration in the pore structure of wood, which can affect in turn wood permeability and impregnation. These data will be helpful for predicting the permeability and impregnation of wood after microwave treatment.
Highlights
IntroductionPermeability is an important physical property of wood that affects its drying properties, impregnation, and sound absorption [1–4], determining many of its applications as a porous material
Taghiyari and Avramidis [10] reported that applying the silver nano-impregnation process to heat treatment promotes microcracks in the wood cell wall, which has a positive effect on permeability
The spruce average sound absorption coefficients at 2000– 5000 Hz were higher by 6.9% for the transverse section, 20.0% for the radial section, and 31.7% for the tangential section
Summary
Permeability is an important physical property of wood that affects its drying properties, impregnation, and sound absorption [1–4], determining many of its applications as a porous material. Various special methods for improving permeability have been studied, but the most widely used wood modification is heat treatment. Heat treatment disrupts wood cell walls and expands the intercellular space [7]. From this change, heat-treated wood has increased pore size and porosity and improved gas permeability [8, 9]. Taghiyari and Avramidis [10] reported that applying the silver nano-impregnation process to heat treatment promotes microcracks in the wood cell wall, which has a positive effect on permeability. Kolay and Kang [11] observed cell wall structural changes in steam-exploded Cocos nucifera, a type of heattreated wood modification.
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