Sound scattering by rough elongated elastic objects. II: Fluctuations of scattered field
MetadataShow full item record
KeywordSound waves; Backscattering; Fluctuations; Roughness; Cylinders; Interference; Underwater; Shrimp
Sonar echoes from unresolved features of rough objects tend to interfere with each other. Because of these interferences, properties of the echoes, such as its envelope level, will vary from realization to realization of stochastically rough objects. In this article, the nature of the fluctuations of the backscattered echo envelope of rough solid elastic elongated objects is investigated. A general formulation is initially presented after which specific formulas are derived and numerically evaluated for straight finite-length cylinders. The study uses both the approximate modal-series- and Sommerfeld–Watson-transformation-based deformed cylinder solutions presented in the first part of this series [T. K. Stanton, J. Acoust. Soc. Am. 92, XXX (1992)]. The fluctuations of the backscattered echo envelope are related to the Rice probability density function (PDF) and shown to depend upon δ/a and [script L]/L in the Rayleigh scattering region (ka≪1) and kδ and [script L]/L in the geometric region (ka≫1), where δ is the rms roughness, a is the radius of the cylinder, [script L] is the correlation length of the roughness, L is the length of the cylinder, and k is the acoustic wave number in the surrounding fluid. There are similarities shown between these fluctuations in the geometric region and those from rough planar interfaces. In addition, analytical expressions and numerical examples show that the fluctuation or ``incoherent'' component of the scattered field is random only in amplitude—its phase approaches a constant value, in phase with the mean scattered field, which needed to be taken into account in the formulation. Finally, applications of the theory developed in this article to backscatter data involving live marine shrimp-like organisms are discussed.
Author Posting. © Acoustical Society of America, 1992. This article is posted here by permission of Acoustical Society of America for personal use, not for redistribution. The definitive version was published in Journal of the Acoustical Society of America 92 (1992): 1665-1678, doi:10.1121/1.403906.
Showing items related by title, author, creator and subject.
Stanton, Timothy K. (Acoustical Society of America, 1992-09)By use of the recently published deformed cylinder formulation [T. K. Stanton, J. Acoust. Soc. Am. 86, 691–705 (1989)], the scattered field due to rough elongated dense elastic objects is derived. The (one-dimensional) ...
Equations for normal-mode statistics of sound scattering by a rough elastic boundary in an underwater waveguide, including backscattering Morozov, Andrey K.; Colosi, John A. (Acoustical Society of America, 2017-09)Underwater sound scattering by a rough sea surface, ice, or a rough elastic bottom is studied. The study includes both the scattering from the rough boundary and the elastic effects in the solid layer. A coupled mode matrix ...
Results of research on surface waves of the western North Atlantic. I. Investigation of bottom pressure fluctuations and surface waves. II. Results of sea surface roughness determinations in the vicinity of Woods Hole, Mass., and Bermuda Seiwell, Harry Richard (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 1948-08)Part I: It is to be expected that in the future, measurements of pressure fluctuations beneath the ocean surface will provide basic data for solution of many practical problems on the state of the sea. As a result of the ...