LAUSR

Acoustic metasurfaces with subwavelength unit cells modulating the phase of sound wave were developed to realize beam forming, steering, focusing, and recently carpet cloaking. However, these metasurfaces were used for small phase gradient applications and the ability to cloak or mimic reflection surfaces with rapid change profiles remained unexplored. Here, we analytically and experimentally investigate the effect of rapid change in-plane phase gradient on the design of acoustic metasurfaces for carpet cloaking and diffusing applications. Helmholtz resonators with different neck radii are used to form the ultrathin metasurface in our study. The variation of neck radius of the Helmholtz resonator results in different reflection phase of acoustic wave. In both analytical and experimental results, the large in-plane phase gradient does not affect the carpet cloak design, which is solely depending on the phase correction of the local profile height. On the contrary, the impedance mismatch resulted from the r...