Angle-insensitive acoustic metamaterial plane with extraordinary transmission using two embedded and coaxial split spherical shells

In this work, an extraordinary acoustic transmission transparency window with an angle-insensitive acoustic metamaterial plane is proposed and investigated numerically and experimentally. The cell of the metamaterial plane consists of two embedded and coaxially split spherical shells arranged in a square lattice, and the extraordinary acoustic transmission transparency window is caused by the resonance coupling of two embedded split spherical shells. The simulation results reveal that the designed plane has a frequency-selective transparent window with angle insensitive to incident waves. To obtain experimental evidence, the designed samples are fabricated by three-dimensional (3D) printing technology and measured using an acoustic impedance tube testing system. The transmission exported from the experiment coincides with the simulation predictions, which further proves the existence of the acoustic-frequency-selective transparent window caused by the resonance coupling. This phenomenon revealed in the present contribution is widespread and is expected to be utilized for fabricating and designing novel acoustic devices.