Abstract: It is easy to open some the complete band gaps for phononic crystals (PCs) since the symmetry reduces for the complex lattices. The properties of multiple point defects in a PC composed of a (32.4.3.4) array of circular steel cylinders in water are studied experimentally. The band structures of PCs with multiple defects of different zigzag types are computed by the finite element method with the supercell approximation. A good agreement between the numerical and experiment results is shown. The effects of the number of the multiple point defects of the Zigzag type decide on the localized modes, the eigonmodes and the waveguide in the band gaps of high or low frequencies are discussed. These defect studies of PCs with complex lattices can be further used to improve the design of new acoustic devices.

Key words: (32.4.3.4) lattice, band structure, multiple point defects of Zigzag type, phononic crystals, transmission spectra