An experimental study on changes in sound absorption capability of spruce (Picea sitchensis), Douglas fir (Pseudotsuga menziesii), and larch (Larix kaempferi) after microwave treatment

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.

Analysis of the Influence of Microwave Treatment Parameters of Wood

“…Hence, even in the face of the growing number of research works investigating the use of MW technology to increase the permeability of wood species, there is still a need to conduct research with different species aiming to investigate the improvements in the permeability [11], and especially verify the effects on the mechanical properties of small clear and structural size specimens. In this sense, this work presented results that can guide future investigations.…”

“…Recent works have provided important information showing that MW treatment improves wood's permeability, mainly of refractory species, which allows, for example, a more effective impregnation of preservative agents [3,[7][8][9][10]. Jang and Kang [11] highlight that MW technology is utilized in the wood industry to improve the effectiveness of wood drying. In addition, MW treatment is an environmentally friendly, cost-effective, and time-saving method that has been shown to significantly shorten processing times while improving drying quality [3,7,[12][13][14].…”

Investigation of Sound Absorption Ability of Acanthopanax senticosus Wastes

“…Previous studies have reported that the pore structure of wood has a sound-absorbing effect (Jang and Kang, 2021a, 2021dJiang et al, 2004;Taghiyari et al, 2014). When wood is subjected to heat treatment such as high-temperature oven-drying, microwave, or steam explosion, the pores are converted into an open-pore structure, and the sound absorption performance can be further improved (Jang and Kang, 2021b;Jang and Kang, 2022;Kang et al, 2021). A. senticosus is boiled at a high temperature for a long time to obtain the extract for herbal medicine.…”