Acoustic Resonance Scattering by Submerged Elastic Shells

Abstract

We review a number of instances in which classical acoustic wave scattering from submerged elastic shells can be analyzed in the resonance region of their spectra. We recently reviewed (Refs 42, 43, 12) the cases dealing with acoustic resonance scattering from solid elastic bodies, or with elastic resonance scattering from fluid or solid inclusions in elastic media. It only remains for us to address the works dealing with submerged shells, which we analyze here. We study scattering by bare or viscoelastically coated spherical and cylindrical shells in water, by means of (exact) normal-mode solutions, and by spheroidal shells by numerical approaches, particularly via the T-matrix method. We consider the shell responses mostly in unbounded media and when the interrogating waves are plane and c.w., although some recent findings valid for pulsed incidences and in the vicinity of environmental boundaries are also included. We use the methodology of the resonance scattering theory (RST) as much as possible, emphasizing its post-1981 results. High-frequency findings, obtained by asymptotic methods, are extrapolated to lower frequencies, to confirm RST predictions for the intermediate spectral regions in which the most important structural resonances are known to reside. A large number of bibliographical entries are collected and discussed in connection with our approach.