Resonant Acoustic Scattering by Spherical Air-Filled Elastic Shells Submerged in a Fluid: Comparison of Theory and Experiment

Theoretical model of acoustic scattering by submerged thin elastic air-filled spherical shells is compared with the results of direct measurements in an underwater test facility. Elastic resonances arising in elastic shells significantly affect the scattering, as demonstrated both theoretically and experimentally. Measurements were carried out in two frequency ranges. Two kinds of resonances—extensional and bending—were expected. In the low-frequency range, a predicted sharp drop in back scattering is observed, which corresponds to an extensional resonance mode. In the high frequency region, an expected wide resonance zone with enhanced scattering was found, although differing from the theoretically predicted distribution of resonances, which may be attributed to slight imperfection of the shell used in the experiment.