Underwater sound absorption of a meta-absorption layer with double negativity

Abstract

An underwater meta-absorption layer (MAPL) is presented which consists of multiple steel scatters and a rubber matrix. Double negativity of the MAPL can be found within multiple frequency ranges with the effective medium method due to local resonance and wave scattering. By using the finite element method (FEM), the sound absorption of the MAPL with steel plate backing is calculated. Results show that the more scatters inserted, the higher sound absorption can be obtained at multiple frequency ranges. Longer scatter length promotes the absorption peaks to higher magnitudes and higher frequency ranges. Larger damping leads to higher energy dissipation. Moreover, graded scatter spacing and anti-graded scatter length promote the sound absorption peaks to higher magnitudes. The results of the low-frequency range absorption peaks are owing to the monopole and dipole resonances, which convert the longitudinal waves into shear waves and dissipate the energy through structural damping. Investigation in this article has promising potential in underwater sound absorption for underwater vehicles.