Improvement of Sound Absorption Capability of Wood and wood-based Board by Resonant Absorption

공명흡음에 의한 목재와 목질보드의 흡음성능개선

Improvement of sound absorption capability of wood and wood-based board by resonant absorption was attempted. Sound absorption coefficients of wood and wood-based board which contain normal, simple perforation and stair type perforation had been estimated by the tube method using standing wave ratio. Sound absorption coefficients of wood specimens of simply perforated and perforated with stair were higher than that of normal specimens. Especially, in case of stair type perforation, it was about 50 to 60% higher than that of normal specimen in the frequency of 3 to 4KHz. It was considered that the cavity which had been formed by perforation with stair type behaved as a single resonator. Wood-based board showed good sound absorption coefficients in the frequency from 125Hz to 2KHz and that of perforated board showed a little higher in the frequency from 300Hz to 500Hz than that of normal board. The computed data of resonant frequencies at several sizes of cavity showed good accordance with the estimated data of those.

공명흡음에 의해 목재와 목질보드의 흡음성능을 개선하고자 무천공, 단순천공 그리고 계단형으로 천공한 목재와 목질보드의 흡음률을 정재파비를 이용하는 관내법으로 조사하였다. 그 결과 측정주파수범위에서 계단형으로 천공한 시험편이 보통의 시험편보다 높은 흡음률을 나타내었으며, 특히 3~4KHz의 주파수영역에서는 50~60% 정도 높은 흡음률을 나타내었다. 목질보드는 측정주파수범위에서 높은 흡음률을 나타내었으며 천공한 목질보드는 300Hz에서 500Hz의 주파수 영역에서 조금 더 높은 흡음률을 나타내었다. 이는 시험편에 조성한 계단형 천공이 단일공명기로 작용하여 특정주파수영역에서 흡음률이 증가된 것으로 사료된다. 몇 가지 크기의 공극에 의해 공명이 발생하는 예상주파수는 실측한 주파수-흡음률 곡선에서 외삽한 공명주파수와 잘 일치하였다.