Absorptive properties of three-dimensional phononic crystal

We consider the absorptive properties of three-dimensional phononic crystal (PC) composed of steel spheres arranged in viscoelastic rubber. The mode conversions during the Mie scattering of a single steel sphere in unbounded rubber are analyzed in detail. Then the multiple scattering (MS) and absorption effects induced by the simple cubic lattice and the viscosity of the rubber are investigated by the MS method. The results show that the shear and viscoelastic properties of the rubber are crucial, and the destructive interface induced by MS below each Bloch frequency enhances the absorption. Finally, the acoustic properties of finite PC slabs variation with the filling fraction and the incident angle are discussed for a variety of cases. The results show that the PC can be used as underwater anechoic material.