Abstract
We investigated the effect of ultrasonic treatment on Malas (Homalium foetidum) gas permeability and sound absorption coefficient using the transfer function method. Results showed a longitudinal average Darcy permeability constant of 2.02 (standard deviation SD 0.72) for untreated wood and 6.15 (SD 3.07) for ultrasound-treated wood, a permeability increase of 3.04 times. We also determined the average sound absorption coefficients in the range of 50 to 6.4 kHz and NRC (noise reduction coefficient: average value of sound absorption coefficient value at 250, 500, 1000, and 2000 Hz) of untreated Malas. Those values were 0.23 (SD 0.02) and 0.13 (SD 0.01), respectively, while those of ultrasonic-treated Malas were 0.28 (SD 0.02) and 0.14 (SD 0.02), a 19.74% increase in average sound absorption coefficient.
Highlights
Wood permeability greatly influences drying characteristics [1], chemical impregnation [2–4], and sound absorption in the longitudinal direction [5, 6]
These results show that the ultrasonic sound treatment influences permeability changes [15]
Kang et al reported that vessel and the single perforation plate of hardwood behave as through pores that are effective for sound absorption [19]
Summary
Wood permeability greatly influences drying characteristics [1], chemical impregnation [2–4], and sound absorption in the longitudinal direction [5, 6]. Kanagawa et al reported that steam explosion treatments improve wood’s permeability and drying rates [7]. Various researchers have reported that improving gas permeability increases the ability to treat wood chemically [2–4]. Permeability increases were affected by pore size and through pore content [8, 9]. Jang and Kang used heat treatment to investigate changes in gas permeability, pore size, and pore shape [10]. As the heat treatment temperature increased, pore size and through pore porosity increased, In previous research, Kang et al reported that delignification treatment using Wise’s method improved Larix kaempferi’s permeability and the cross-sectional surface sound absorption coefficient [11]. Permeability improved after low-pressure steam explosion treatment [5], heat treatment [10], and organo-solvent treatment [6]
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