Abstract
AbstractIn this study, the sound absorption coefficient of three low density hardwoods – binuang, balsa and paulownia – were investigated. Their gas permeability and pore size were measured, and their pore shapes were classified into through pore, blind pored, and closed pore, as specified by the International Union of Pure and Applied Chemistry (IUPAC). Among the three species, obvious that paulownia had lowest sound absorption when the two of others showed higher sound absorption. Although paulownia is a high porosity wood, most of its vessels are blocked by tyloses; it is therefore difficult for sound waves to enter its pores, which results in poor sound absorption performance. This study showed that the higher the through pore porosity, the higher was the gas permeability, which led to improvement of the sound absorption performance. It was also found that the sound absorption coefficient of the three species woods increased at low frequencies as the size of an air cavity between the specimens and tube’s wall increased.
Highlights
IntroductionThe elimination of outdoor noise pollution is one of the main concerns regarding the quality of housing
Paulownia is a high porosity wood, most of its vessels are blocked by tyloses; it is difficult for sound waves to enter its pores, which results in poor sound absorption performance
This study showed that the higher the through pore porosity, the higher was the gas permeability, which led to improvement of the sound absorption performance
Summary
The elimination of outdoor noise pollution is one of the main concerns regarding the quality of housing. Smardzewski et al (2014) reported that high porosity wood is effective as a sound-absorbing material because it exhibits a small specific impedance. Xu et al (2004) reported that sound absorption properties depend on density and thickness in kenaf binderless particleboards. Kang et al (2012) reported that the lower the density, the higher the sound absorption coefficient in board manufactured from miscanthus particles. This is because the lower the density, the higher the pore content, so that more sound waves are diffusely reflected and lose energy. Mohammad et al (2010) investigated the sound absorption of Malaysian wood using the Delany-Bazley approximation method, and reported that high frequency sound absorption was high in low density wood
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