Tunable Fluid-Type Metasurface for Wide-Angle and Multifrequency Water-Air Acoustic Transmission
The design of the fluid-type metasurface for water-air acoustic transmission. (a) The FAM enables the communication between fish and birds. (b) and (c) The side and top view of the structure of metasurface. (d) The unit of the FAM for finite element method (FEM) calculations. (e) The transmission enhancement of the FAM vs. frequency is obtained with the FEM calculations. The parameters of ,, and are fixed as 5.11 mm, 3 mm, and 1.2 mm, respectively. The variable is defined by the different . (f) The FEM results for the water-to-air oblique incidence with an angle of . The is fixed as 1.6, and other parameters are same as in (e). The thermal and viscous losses are considered in (e) and (f).