Using an exact Mie scattering solution, the scattering and vibration mode of a single air sphere in unbounded rubber are analyzed with reference to the elements of the scattering matrix. Then, using the multiple_scattering method, the anechoic properties of the viscoelastic rubber coating (with a thickness of 8mm) containing a plane of periodically distributed air spheres are investigated under different backing conditions. The results show that the excellent anechoic performance of the coating originates from the dilatational resonance of each air sphere. The anechoic coating can attenuate most incident energy and minimize reflection in the resonance frequency region. Finally, a bi_layer coating (with a thickness of 20mm) is designed for broad_band anechoic material.