The locally resonant sonic material (LRSM) is a kind of structural composite. Such composite typically consists of an elastic matrix periodically embedded with metallic spheres, which are coated with soft rubber. Owing to its capability of controlling the low frequency sound, the LRSM has a promising prospect in the application of underwater acoustic materials. This paper proposes a mass-damper-spring model to explain the sound absorbing mechanism of the LRSM, and derives analytical formulae to evaluate the absorbing performance. After reasonable simplification, the analytical formulae can intuitively illustrate the relationship between the absorbing performance and the parameters of the LRSM. The correctness of the physical model was verified by comparing the analytical evaluation with the numerical result calculated by the layer-multiple-scattering method. The result shows that the sound absorption of the LRSM is induced by the energy dissipation of the damped local resonator subjected to excitations. The influence of the parameters on the absorbing performance of the LRSM is analysed systematically. It is shown that a resonator with a heavier core and a stiffer coat can produce a better sound absorbing performance.
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