A finite solid impedance matching mechanism with large bandwidth for acoustic transmission between water and air

A purely solid impedance matching mechanism of finite length is shown to produce broadband acoustic transmission between air and water. The two-dimensional "flex-layer" device comprises three plates separated by ribs aligned in the third dimension. A similar structure was investigated in previous papers under the assumption of an infinite periodic system, which left the physical length of the structure unclear for practical implementation. Here, we examine the finite size of the structure and demonstrate that beyond a certain number of ribs, the transmissivity does not change significantly. A combination of numerical analysis and finite element simulations (finite element analysis) demonstrates that as the number of ribs increases, the performance of the finite structure approaches the infinite case. This convergence confirms earlier findings and emphasizes the importance of the number of ribs in enhancing transmission performance. Radiation patterns of the transmitted pressure field are studied across a range of excitation frequencies, incident angles, and structural parameters. The study also examines the roles of boundary conditions and material damping. Although the analytical model assumes pinned-pinned boundaries, we show that for suitably long plates, the effect of switching to fixed-fixed boundaries is negligible. Numerical results show that the energy transmission performance decreases slightly when the material loss factor is included.