Switchable asymmetric acoustic field modulation via bilayer coding waveguide arrays

In this work, the acoustic coding waveguide array of a bilayer configuration is proposed to realize asymmetric acoustic field modulation. The designed device is composed of two types of meta-atom, Helmholtz resonator, and air cavity, with high transmittance and opposite phase responses, through which the plane wave is shaped into a focusing beam or splitting beam when input from one side but hardly transmitted when input from the other side. More uniquely, the device can be switched from unidirectional to bidirectional transmission relying on the tunable gap between two composing layers, showing potential applications in acoustic communication, isolation, and stealth.