Phononic crystals have received some attention in the last decade due to their intrinsic property of band gaps. A band gap is a frequency range that acoustic waves cannot propagate within the periodic structure. In this paper, we propose a two-dimensional hexagonal phononic crystal that is composed of lead cylinders embedded in a polyethylene matrix. Using the finite element method, the dispersion diagram is calculated to identify the existence of band gaps. In addition, when a coating layer is introduced between the inclusion and the matrix, we find that the bandwidth and values of the gaps can be adjusted. In our demonstration, the band gap appear to be within the audible range with frequency 15400～18000Hz. Thus, the present proposition may have potential applications in blocking high-frequency noise.
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