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KMID : 0381319770160040127
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Korean Journal of Occupational Health
1977 Volume.16 No. 4 p.127 ~ p.132
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Noise Reduction by Enclosure using Korean-made Plywood and Glass fiber
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Abstract
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In industrial areas where noise level and the worker exposure time exceed the criteria, an evaluation should be made to determine the most economical solution to the problem. A large reduction in noise can be achieved by complete enclosure of a noise source. This study was carried out to determine the effect of Korean-made meterials in noise reduction. A blower producing noise level of 91 dBA was used as a noise source, and plywood having surface desity of 9.5 ㎏/㎥ and thickness of 1.8㎝ was used as sound-isolating partition and glass fibers of various densities and thicknesses were used as sound absorbing materials. Noise reduction effect of total and parial enclosures was evaluated.
The results are summarized as follows.
1. When the blower was enclosed with an unlined enclosure constructed by plywood, the noise reductions by total and partial enclosures were 17㏈ and 9 ㏈ respectively at A-weig-hted measurements, which indicated lowere effectiveness than the theoretical effect of the plywood. This could be resulted from the reverberant buildup in the enclosure.
2. To reduce the reverberation, glass fibers of various densites and thicknesses were covered inside the wall of enclosure and the effectiveness was as follow.
1) Noise reductions by plywood plus glass fibers having densities of 25-48 ㎏/㎥ were 20-25 ㏈ and 30 ㏈ respectively.
2) Noise reductions at 4,000 ㎐ by plywood plus 48 ㎏/㎥ glass fibers having thicknesses of 2.5㎝ and 5.0㎝ were 31 and 41 ㏈ respectively. By doubling the thickness of glass fibers the noise reduction increased by 5 ㏈ at A-weighting.
3) The difference in noise reduction between total and partial enclosure was ranged from 5 ㏈ to 11 ㏈ at A-weighting. The higher the density of glass fibers were, the differnece increased.
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