Measurements and analysis of acoustic backscattering by elastic cubes and irregular polyhedra

Abstract

Underwater acoustic studies of backscattering by submerged targets have generally focused on bodies with spherical and cylindrical symmetry. However, there are interests in scattering by objects which may be characterized by more angular features, with surfaces that tend to be composed of facets and edges. To investigate the scattering properties of such bodies, the backscattering by a number of elastic cubes, and irregularly shaped polyhedra, have been studied. Data were collected by measuring the band limited impulse response of the scatterers, using a broadband transducer, which operated as a transceiver, both transmitting and receiving signals. To present the scattering measurements nondimensionally a form function definition has been employed to normalize the backscattered signals. The normalized frequency has been expressed as ka, where k is the acoustic wave number, and a is a characteristic dimension of the scatterer. The cube observations covered a broad ka range, kaϭ3 -34, thereby encompassing the lower ka scattering region where the cube can be considered to be nominally rigid, through to higher ka values where it would be expected that the elastic properties of the cube become important. The measurements on irregular polyhedra are more limited in extent, however, the results are presented for comparison with the cube data. To compare the observations with predictions, computations of acoustic backscattering for both rigid and elastic cubes are presented.

Measurement Method of Turbidity Depth Profiles using ADCP for Monitoring of Coastal Sea Area

“…(1) into Eq. (2) and noting the directivity of the transducer on reception gives Hay et al [13] and Throne et al [5] obtain the relationship between concentration (M) of the solids and the voltage (V) due to the scattering pressure derived from Eq. (3), and confirmed this relationship experimentally.…”

“…In logarithmic scale, the so-called sonar equation derived from simplifying Eq. (4) is the following; logM O=.lx{Kc(E -Er)+2ra+20logr}-2logk,k, (5).…”

“…Thorne et al [5], [6], Hay et al [7], [8] and Vincent et al [9] have shown that the turbidity profiles can be measured accurately in sea.…”

Modeling analysis of ultrasonic attenuation and angular scattering measurements of suspended particles

“…Experiments for the fundamental understanding of angular sound scattering from spheres have been performed in the past [41][42][43][44] and even irregular particles were considered. [45][46][47] Most work on the bistatic case is based on the extensive work by Hay. This includes the assessment of the sound scattering and absorption theory, 13 experimental studies, [48][49][50][51][52] and rigorous comparison of data with the literature model.…”

Scattering of a normally incident plane wave by a rigid rectangle

“…There has, for example, been considerable interest recently in the scattering by solid elastic cubes (Chinnery et al . 1997;Thorne et al . 1997;Gipson & Marston 1999).…”