Orientation dependence for backscattering from a solid cylinder near an interface: Imaging and spectral properties

Abstract

When a solid cylinder lies proud on horizontal sand sediment significant contributions to backscattering, specular and elastic, involve multipath reflections from the cylinder and interface. The scattering structure and resulting spectrum versus azimuthal angle, the “acoustic template,” may be understood using a geometric model [K. L. Williams et al., J. Acoust. Soc. Am. 127, 3356–3371 (2010)]. If the cylinder is tilted such that the cylinder axis is no longer parallel to the interface the multipath structure is modified. Some changes in the acoustic template can be approximately modeled using a combination of geometric and physical acoustics. For near broadside scattering the analysis gives a simple expression relating certain changes in the template to the orientation of the cylinder and the source geometry. These changes are useful for inferring the cylinder orientation from the scattering. Changes to the template at end-on and intermediate angles are also examined. The resulting acoustic images show s...