Acoustic metamaterial with split hollow spheres

We propose an acoustic metamaterial (AM) composed of local resonant split hollow sphere (SHS). The results of numerical simulation and acoustic experiment show that the effective modulus of the AM with SHS is negative. To further investigate the intrinsic resonant mechanism of the SHS, we study the transmission of the AM by adjusting the geometry sizes of the SHS, such as the diameter of split hole and the diameter of hollow sphere. It is found that the geometry sizes of SHS will greatly affect the frequency of transmission dip, say, the resonant frequency. Moreover, we investigate the effects of the arrangement in AM on transmission feature. When the lattice constant and the number of SHSs change, the frequency range of resonance in the single-layer AM keeps unchanged. However, the resonant intensity of AM becomes stronger with the increase of the number of SHSs in single layer and the number of SHS layers.