Theoretical study on the sound absorption of acoustic coatings with pre-deformation induced by the hydrostatic pressure.

Underwater acoustic coatings experience changes in geometric and material parameters under hydrostatic pressure. A theoretical method is proposed for investigating the pressure effect on the absorption coefficient of a viscoelastic coating embedded with a cylindrical cavity. Static deformation is analyzed using Murnaghan material model, and an equivalent model with transversely isotropic material behavior is constructed under pressure. The phase velocity and attenuation of the fundamental longitudinal [L(0,1)] wave mode in the stressed acoustic coating are investigated. Results show that increased pressure raises the longitudinal and shear stiffness coefficient related to the L(0,1) mode and induces a reduction in the inner radius and thickness of the acoustic coating. Consequently, the phase velocity of the L(0,1) mode increases and the peak frequency of the absorption coefficient shifts to a higher frequency range. Finally, the effectiveness of the proposed theoretical method is validated by the finite element method.