Sound Absorption Rate and Sound Transmission Loss of Wood Bark Particle

목재수피 파티클의 흡음율과 음향투과손실

Abstract

In this study, sound absorption capability and sound transmission loss of several kinds of target densities and thickness for six species of wood bark particle were estimated by the transfer function and transfer matrix methods. Resultantly, the mean sound absorption coefficient of a 100-mm thick Hinoki wood bark particle mat was 0.90 in the frequency range of 100-6400 Hz, whereas the mean sound absorption rate of a 50-mm thick Hinoki wood bark particle mat was 0.84 in the same frequency range. Particularly, at a thickness of 100 mm, it reached almost up to 100% in the frequency range of 1 KHz. The sound transmission losses of 100-mm thick Hinoki wood bark particle mat with a target density of 0.16 at 500 and 1000 Hz were 15.30 and 15.73 dB, respectively. When a 10-mm thick plywood was attached to the back of the wood particle mat, the sound transmission losses was increased by 20-30 dB. Wood bark can be used as an acoustical material owing to its high sound absorption rate and transmission loss.

목재수피의 음향성능을 파악하고자 6가지 수종의 목재수피를 삭편으로 절삭하여 몇 가지 비중조건과 두께로 만든 후 흡음율과 음향투과손실을 전달함수법과 전달행렬법으로 각각 측정하였다. 그 결과, 편백나무수피가 두께 100 mm 일 때의 100-6400 Hz 평균흡음율은 0.90이며 두께 50 mm 일때의 100-6400 Hz 평균흡음율은 0.84이다. 특히 두께 100 mm 일 때의 경우, 1 KHz의 주파수영역에서의 흡음율은 약 100%에 근접하는 높은 흡음율을 나타내었다. 음향투과손실은 측정주파수범위에서 편백나무수피는 500 Hz에서 15.30 dB의 투과손실을 나타내었고 1000 Hz 수치는 15.73 dB이었다. 10 mm 두께의 합판을 수피파티클 배면에 추가한 후에는 투과손실이 20-30 dB 증가하였다. 목재수피는 친환경적이면서 기존의 석고보드보다 흡음율이 높고 음향투과손실이 크게 나타나서 음향성능이 우수한 건축재료로 고려될 수 있다고 생각된다.

Fig. 1. Wood bark particles of Hemlock, Elm, Douglas-fir, Hinoki, Radiata-pine and Larch wood.

Fig. 2. Sample preparation for measuring sound absorption ratio and sound transmission loss.

Fig. 3. Sound absorption rate of wood bark mat with apparent density of 0.12 (Graph legend values denote sample thickness).

Fig. 4. Sound absorption rate of wood bark mat with apparent density of 0.14 (Graph legend values denote sample thickness).

Fig. 5. Sound absorption rate of wood bark mat with apparent density of 0.16 (Graph legend values denote sample thickness).

Fig. 6. Sound absorption rate of 10mm thick plywood attached wood bark mat with apparent density of 0.12 (Graph legend values denote sample thickness).

Fig. 7. Sound absorption rate of 10mm thick plywood attached wood bark mat with apparent density of 0.14 (Graph legend values denote sample thickness).

Fig. 8. Sound absorption rate of 10 mm thick plywood attached wood bark mat with apparent density of 0.16 (Figure legend values denote sample thickness).

Fig. 9. Sound transmission loss of 100mm thick wood bark mat (Graph legend values denote apparent density of wood bark mat).

Fig. 10. Sound transmission loss of 10mm thick plywood attached 50mm thick wood bark mat (Graph legend values denote apparent density of wood bark mat).