Sound radiation from a fluid-loaded infinite plate with a patch

Abstract

This paper focuses on the solution to the vibro-acoustic response of a line-driven fluid-loaded plate with an elastic patch acting as a distributed inhomogeneity. The patch affects the plate's sound radiation by adding extra loading to the driving force and by scattering structural waves. When the driving force is located beneath the patch, the extra loading reduces the plate's supersonic velocity response and sound radiation. At some frequencies, however, the constructive superposition of scattered structural waves and near-field waves by the driving force outweighs the effect of patch loading and results in an increased sound radiation power. When the patch is located away from the driving force, wave scattering phenomena dominates the plate vibration and subsequent sound radiation. By examining the effect of the length and location of the patch on the sound power, it is possible to relate the changes in the sound power to the changes in supersonic velocity spectrum and velocity distribution contributed by the trapped modes in the patched area and interference between the scattered waves by the patch and the near- and far-field structural waves directly generated by the driving force.

Underwater sound radiation from an elastically coated plate with an embedded and distributed inhomogeneity

“…For the un-coated plate, the attachment of a patch (an SCP) above the driving force causes extra mass loading, resulting in a reduction of driving point mobility and thus an overall reduced level of plate vibration and radiated sound power, as illustrated in detail in Ref. 11. The driving point mobilities of the four configurations are shown in Fig.…”

“…(9) and (10) into Eqs. (11) and (12) and combining Eqs. (5) and (6) gives the boundary conditions of the coating at z ¼ 0,…”

“…When this inhomogeneity is placed on the coating surface and exposed to fluid, the modes may strongly couple with the sound waves in the fluid and result in significant sound radiation or scattering at these resonance frequencies. 1,2,11 However, when the inhomogeneity is embedded in the coating material, the interaction between the local modes and the fluid may be reduced by the coating material between them. This may reduce resonance-induced sound radiation, especially when damping in the coating material becomes significant.…”

“…[1][2][3][4][5][6][7][8][9][10][11] In the earlier investigations, the inhomogeneities were represented by either a crack 3 or a rigid obstacle 7-10 in the material. Andronov et al 3 investigated acoustic scattering by an elastic plate with a narrow crack.…”