Pentamode metamaterials used for sound insulation and band gap controlling consisting of double-cones

In order to effectively insulating or reducing the noise underwater by utilizing the pentamode metamaterials composed of double-cone units which is of great application prospects in the field of acoustics, here a kind of pentamode metamaterial made of the double-cone units with different wide touch diameters was proposed. The phononic band structure, the phase velocities of compression and shear modes and the figure of merit were numerically calculated by using finite element method, and then the influences caused by constituent material parameters and geometric structure parameters were analyzed systematically. Results indicated that the pentamode metamaterial proposed right here obtained a wider, lower-frequency phononic band gap, better stability and lighter weight compared with pentamode metamaterial made of the double-cone with different narrow touch diameters which was reported previously, under the premise that the original pentamode structure's single mode region was still remained even if a certain wide touch diameter individually changing. Consequently, a relatively wide and low-frequency band gap appeared while the particular wide touch diameters individually changing. The figure of merit was mainly determined by the geometric structure parameters. Each constituent material parameters only affects the bandwidth and location in different ways. Therefore, pentamode metamaterial made of the double-cone units with different wide touch diameters is expected to be used for underwater acoustic noise reduction or controlling the phononic band gaps.