Scattering by a mass inhomogeneity on a fluid-loaded elastic plate.

Abstract

The scattering of acoustic waves by a finite length mass distribution attached to an infinite fluid-loaded elastic plate is investigated. The scattered field is made up of two parts, one the specularly reflected wave proportional to the plane wave reflection coefficient, and the other represents the wave scattered by the mass inhomogeneity. The first-order approximation to the latter wave is obtained by a Born-type approximation to the wave-number space integral equation for the plate velocity transform. This is examined to reveal the sensitivity of the scattered field to the magnitude of the mass perturbation, the spatial extent over which the mass is distributed and the degree of continuity of the distribution function, especially at the end points. Three specific distributions are examined, each having the same total mass distributed over a constant length L. For low frequencies, i.e., acoustic wavelength comparable to L, the constant mass distribution is acoustically better than the others, but for higher frequencies, the distribution having the highest degree of continuity at the end points is found to be superior.