Effect of structure on sound absorption and sound transmission loss of composite sheet

The effects of structure on sound absorption and sound transmission loss (TL) of a composite sheet were investigated. Non-woven polyethylene terephthalate fabrics were bonded to the top side and the bottom side of the polypropylene (PP) board by hot press method. The absorption coefficient of the composite sheet using non-woven fabric with a surface density of 0.64kg/m(2) was 0.1~0.2. It showed 100~400% improvement compared to that of plain PP board. TL of a composite sheet was increased with the surface density of PP board and with introducing hemisphere cavities. Two different structures of composite sheet were prepared using flat sheet and sine-wave sheet to investigate the structure effect. The composite sheet A with a sine-wave sheet on both sides of flat PP board showed increased TL of 7dB compared to the composite sheet B with a flat PP board on both sides of a sine-wave sheet.