粒状材料の音響特性に関する基礎的研究（粒径の異なる層が重なる場合の垂直入射吸音率）

摘要

In this paper, several diameter of solid glass spherical grain was dealt. Each diameter grain has the each characteristic impedance and the complex wave constant. At first, the characteristic impedance and the complex wave constant for each grain diameters were measured. Then, the normal incidence absorption coefficient of each grain diameters for arbitrary layer thickness can be calculated. Likewise, the normal incidence absorption coefficient for multilayer with different grain diameters and arbitrary thicknesses can be calculated. This calculation process is comparatively lengthy, so the experiments for real multilayer and the calculations were compared. Result of the calculations coincided to the experiments. Consequently, calculation result of normal incidence absorption coefficient for multilayer with different grain diameters is useful.%多孔質材料は吸音材料として広く使われている．rnまた，吸音が主な目的ではない多孔質材料が副次的なrn吸音効果を持つ場合も，その特性が活用されている．rn多孔質材料は，その厚さや異種材料の重ね合わせによrnり吸音特性が変化する．このように，厚さや組合せをrn変化させた場合，基礎的な実験データを基にして，吸rn音特性を予測できれば有用である．