Abstract
Synthetic aperture sonar (SAS) and frequency response as a function of tilt (acoustic color) are two methods used to study target backscattering. Close proximity to a boundary can affect both the SAS and spectral signatures of a target. To improve understanding of these effects, scaled tank experiments were carried out on solid aluminum cylinders having flat ends and length to diam ratios of 2:1 and 5:1. To partially simulate the mechanisms present when an object is resting on the ocean bottom and illuminated at shallow grazing incidence, the cylinders were suspended through the air‐water interface of a tank. Monostatic measurements were obtained as the source/receiver was scanned along a line parallel to the interface to produce SAS images. Backscattering measurements were also made as the target was rotated in a plane parallel to the interface, with the source/receiver stationary, to give the spectrum (color) as a function of tilt. Some of the elastic features in the SAS images and the acoustic color diagrams could be interpreted using a previously developed ray‐based theory of generalized Rayleigh waves [K. Gipson and P.L. Marston, J. Acoust. Soc. Am. 106, 1673–1689 (1999);, 107, 112–117 (2000)]. [Research supported by ONR.]
Published Version
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