| 摘要 |
PROBLEM TO BE SOLVED: To bring a sound absorbing effect in a wide frequency range by constituting a sound absorber obtained by mixing waste chips made of a plastic and a rubber with a binder and compression molding it by a plurality of surface direction regions having different void fractions. SOLUTION: A material 11c to be molded of a sound absorber 11 is formed of chips having a mean particle size of one type. The material is changed in a lower mold 21a in such a manner that thicknesses are different in a surface direction and an upper surface becomes a waveshape state. And, the material 11c of the state charged in this manner is pressed by an upper mold 21b from above to be compression molded. It is constituted by a plurality of surface direction regions 11a, 11b having different void fractions from one another. The regions 11a, 11b have different frequency bands in the surface direction and a specific sound absorbing performance having different sound absorption coefficient. Therefore, the absorber 11 performs the sound absorbing performance in a wide frequency band. For example, it can be suitably adopted as a sound absorber laid on rails of a railway, a sound absorber applied to a sound shielding wall of a building, a sound absorber to be applied to a vehicle or the like. |
