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(機械力学,計測,自動制御)  [in Japanese] Basic Study for the Acoustic Characteristics of Granular Material : Normal Incidence Absorption Coefficient for Multilayer with Different Grain Diameters(Mechanical Systems)  [in Japanese]

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.