Isolated feature extraction from composite short pulse scattering data for a thin submerged elastic plate.

Abstract

Robust interpretation of observables in acoustic scattering data from submerged elastic structures requires decomposition of composite effects into interacting isolated effects, each of which is matched as well as possible to the relevant wave dynamics. Having selected what one believes to be an observable-based parametrization (OBP), one may then proceed to process the data so as to link the observable features with the wave objects that synthesize them. This strategy is applied here to two-dimensional scattering of a line-force-excited short pressure pulse by a submerged thin elastic plate of finite width. The database is generated numerically by a time domain (TD) finite difference code, with observers located on a line parallel, and exterior to, either side of the plate. The selected OBP involves hybrid combinations of ray acoustic geometrically reflected and edged diffracted fields, with coupling to the supersonic (leaky) compressional mode in the plate, and with collective responses due the multiple interactions between the plate edges. The TD processing is built around auxiliary numerical problems that involve a semi-infinite plate and an infinite plate which, respectively, isolate single-edge diffraction and geometrical reflection. By subtracting these numerically from the composite data, one may isolate the TD edge diffraction coefficient, the leaky mode detachment coefficient, and other OBP quantities. The processing is also performed in the radon transformed time-slowness domain. [Work supported by ONR.]