ACOUSTIC PROPERTY OF SLIGHTLY COMPRESSIBLE POROUS MEDIA AND UNDERWATER STRUCTURE-BORNE NOISE REDUCTION

The weakly compressible viscoelastic medium permeated with micro-bubbles has strong dispersive because of bubbles. The effective sound speed which can be obtained by effective medium method is very small at low frequency range. Based on the acoustic wave equations and boundary conditions, a method is applied to analyze the reduction of underwater structure-borne noise generated by an axially symmetric ring force on the interior of cylindrical shell. The structure-borne noise reduction is simulated for the baffle layer of slightly compressible porous material. The effects of porosity, thickness, damping and shear modulus of matrix are studied. Numerical simulations have confirmed that the underwater structure-borne noise can be reduced effectively by the porous media. This work is helpful for designing the underwater noise control material.