  The investigation of metasurface, which is of great current interest, has
opened up new degrees of freedom to research metamaterials. In this paper, we
propose an ultrathin acoustic metasurface consisting of a series of
structurally simple drum-like subunit cells. Eight units with different sizes
aer selected to realize discrete transmisson phase shifts ranging from 0 to 360
degrees ar 3.5 KHz. The designed metasurface is capable of manipulating sound
waves at will, including anomalous refraction and conversion of propagating
waves into surface waves, which can be predicted precisely by the generalized
Snell's law. It id worth noting that the total thickness of such planar
metasurface is approximately 1/5 of working wavelength, which may be beneficial
to the miniaturization and integration of acoustic equipment.
