Broadband high-index prism for asymmetric acoustic transmission

Abstract

Narrow bandwidth and wavefront distortion are two shortcomings of some existing asymmetric acoustic transmission devices. In this letter, we propose a high-index prism for realizing broadband asymmetric acoustic transmission with uniform plane wave outputs. Numerical simulations and experiments are carried out to verify the theoretical prediction. The experimentally measured acoustic pressure fields, the energy transmission contrast, and the refracted angle in the high transmission direction are in good agreement with the numerically simulated results. Both the simulated and measured energy transmission contrast exceeds 10 dB within the broad frequency range of 2000 to 3500 Hz. The broadband performance is attributed to the spiral unit cell employed to construct the prism, which features a high refractive index within a broad bandwidth. Besides, the transmitted waves in the high transmission direction are uniform plane waves. Our approach provides a practical method to design a broadband asymmetric acoustic transmission device with uniform plane wave outputs and has potential in various applications, such as noise control and medical ultrasound.