Tungsten carbide spheres are used as calibration targets in laboratory acoustic scattering measurements. Though the steady-state response of any metal sphere in water greatly differs from a rigid body return, over almost the entire frequency spectrum, the rigid body and elastic returns can be separated in a short pulse, broadband experiment. This rigid body echo can then be used as a reference to normalize the scattering returns from targets of interest.
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Dragonette et al. (1981) studied this question.