Two-dimensional acoustic metamaterial with negative modulus

We designed a two-dimensional acoustic metamaterial with periodical array of split hollow sphere (SHS) and investigated its transmission behaviors in the impedance tube system. The results showed that the acoustic metamaterial exhibited a transmission dip and inverse phase close to 5 kHz, which indicated the local resonance of SHS. Based on the homogeneous-media theory, the effective modulus of the acoustic metamaterial was calculated to be negative. The finite element method and resonant model simulation results also confirmed the local resonance and negative response in acoustic metamaterial, which agreed well with experiment results. This metamaterial is able to achieve the double negative acoustic metamaterial conveniently by arraying acoustic "atoms" with negative mass density in the matrix.