Design and Demonstration of Acoustic Bends with Metamaterials

In this paper, we propose the design of the broadband acoustic bends in air. Using the perforated plates with various hole-sizes, the bend structure is firstly realized and experimentally demonstrated in a 2D waveguide. The perforated plates only tune the effective density, resulting in impedance mismatch of the structure. Then, by introducing side pipes with various volumes, the impedance of the acoustic bend is further modulated. Both the simulated and experimental results verify that the acoustic beam can be rotated smoothly through these bends in a wide frequency range. After adjusting the impedance, the transmission intensity of the bend is higher than 90%. The good performance of the acoustic bends shows their potential applications in many fields, like detection and absorption in pipelines.