Tunable Asymmetric Transmissions Via Anisotropic Acoustic Metamaterials

An acoustic prism for asymmetric transmissions is proposed, designed, and fabricated by an anisotropic metamaterial composed of an array of controllable C-shaped meta-atoms. Due to the anisotropic configuration of the meta-atom, the effective refractive index of the prism can be continuously tuned by rotating the meta-atom. It is demonstrated that the transmitted wave direction of an incident acoustic wave from one direction can be controlled in real time, as the rotation angle of meta-atom changes gradually. Meanwhile, the incident acoustic wave from the opposite direction will be blocked all the time. Furthermore, a wide range of transmitted angles can be obtained by reshaping the prism, which can work in a broadband (4400-5200 Hz). The results are verified through theoretical predictions, numerical simulations, and experimental measurements. The method can be extended to realize other kinds of tunable asymmetric transmissions of waves via anisotropic metamaterials with controllable meta-atoms.