LAUSR

A multiband acoustic metamaterial (AM) with negative modulus is presented. To realize the multibands, we conduct the unit structure of a resonator with multilayers in which we adjust the number of layers of local resonance cells, namely, multilayer split hollow spheres or cubes (SHSs or SHCs). The results obtained by the finite element method show that a single-layer SHS has one transmission dip and the resonance generates a negative modulus; two-layer SHSs exhibit two transmission dips, while three-layer SHSs and three-layer SHCs have three transmission dips and their dynamic modulus become negative near the resonant frequency. Thus, the number of multiband resonant frequencies is regulated by adjusting the number of layers. This regulation is independent of the sphere and cube of the resonance cell, and this structure is simple. The developed multiband AM can easily be coupled to other structures with negative mass density, thereby obtaining a double-negative AM. It is also applicable in fields such as cloak or sub-wavelength imaging.