High frequency imaging and elastic effects for a solid cylinder with axis oblique relative to a nearby horizontal...

The calibrated acoustic backscattering spectrum versus aspect angle, also called the "acoustic color" or "acoustic template," of solid cylinders located near a flat interface was previously studied for the case where the cylinder axis was vertically oblique relative to the interface and was insonified by a beam at a non-zero grazing angle. The presence of the interface allows for multiple paths by which sound is backscattered. These multipaths are highly dependent on the relative orientations of the target, the interface, and the source/receiver. In this work, the effects of vertical obliquity on the reconstructed synthetic aperture acoustic images is presented. Several robust orientation dependent features are considered and the physical mechanisms responsible identified through geometric arguments. Information about a target's three-dimensional orientation and size may be gleaned from these images, aiding the interpretation of features within the target's acoustic template. Specific features observed in the reconstructed image are associated with features in the acoustic color. The coupling conditions for surface elastic waves are also considered.