A reconfigurable magnetorheological elastomer acoustic metamaterial

Resonant acoustic metamaterials (AMMs) are structures with intrinsic resonances designed to interact with acoustic wavefields to enable applications like low-frequency sound mitigation using materials much smaller than the wavelength affected. However, the addressable frequency range of the AMM is set at the time of manufacture by the geometry, materials, and construction. In this work, a reconfigurable magnetorheological elastomer (MRE)-based AMM is proposed to alter the addressable frequency range without the need for remanufacture. By changing the spatial placement and the mass of neodymium magnets attached to the MRE plate by magnetic attraction, it is possible to engineer the mode shape of the MRE-AMM and tune the absorption, transmission loss, and effective density. It is shown through simulations and experiments that the MRE-AMM can affect wavelengths in air up to 13170x greater than its own thickness.