Tunable sound directional beaming assisted by acoustic surface wave

We investigate the tunable directional beaming of sound wave from a subwavelength slit surrounded by asymmetric surface gratings. The surface gratings are optimally designed to directionally couple the modulated acoustic surface wave modes into surrounding medium along specific direction. The underlying mechanism of direction tuning is explored by the means of wave-vector analysis. The theoretical results predicated by the wave-vector analysis are in good agreement with the numerical results obtained using full-wave simulation. We observe that the full width at half maximum of the sound beam is less than 5 degrees within a wide beaming angle region, and the beaming angle can be tuned by the structural parameters of surface grating.