Experimental demonstration of a broadband waterborne acoustic metasurface for shifting reflected waves

A broadband waterborne acoustic reflective metasurface is developed and investigated in this study, theoretically and experimentally. With a thickness less than one-third of the peak working wavelength, the metasurface can shift the direction of propagation of backward waves reflected from a rigid wall. In order to ensure a broad working band, the proposed metasurface was assembled from a series of pentamodal unit cells with different effective bulk moduli and mass densities. In order to ensure fabricability, the effect of manufacturing precision on the ranges of the effective properties was analyzed. Then, the device was fabricated by wire cut electrical discharge machining-low speed technology. Shifts in the broadband reflected waves of 15 degrees were observed in both finite element simulations and underwater measurements (6kHz-18kHz). These results contribute to understanding and application of broadband control of waterborne reflected acoustic waves.