Spectral analysis of bistatic scattering from underwater elastic cylinders and spheres

Far field sound scattering from underwater elastic spheres and finite cylinders is considered over the full range of scattering angles. Three models for the frequency response of the scattered field are evaluated: a hybrid finite element/propagation simulation for a finite cylinder with broadside illumination, an approximate solution for the finite cylinder, and the exact solution for a sphere. The cylinder models are shown to give comparable results, attesting to the strength of the finite cylinder approximate solution. Interference and resonance structure present in the frequency response of the targets is identified and discussed, and the bistatic spectra for a variety of elastic sphere materials are presented. A thorough understanding of the complicated angle and frequency dependence of the scattering from simple elastic targets is helpful for interpretation of backscattering data from targets at or near an interface, or for scattering data taken by moving automated underwater vehicles, acoustic arrays, or other forms of data collection involving bistatic scattering.