Acoustic scattering by benthic and planktonic shelled animals

View/ Open
Date
2000-08Author
Stanton, Timothy K.
Concept link
Chu, Dezhang
Concept link
Wiebe, Peter H.
Concept link
Eastwood, Robert L.
Concept link
Warren, Joseph D.
Concept link
Metadata
Show full item recordCitable URI
https://hdl.handle.net/1912/2517As published
https://doi.org/10.1121/1.429584DOI
10.1121/1.429584Abstract
Acoustic backscattering measurements and associated scattering modeling were recently conducted on a type of benthic shelled animal that has a spiral form of shell (Littorina littorea). Benthic and planktonic shelled animals with this shape occur on the seafloor and in the water column, respectively, and can be a significant source of acoustic scattering in the ocean. Modeling of the scattering properties allows reverberation predictions to be made for sonar performance predictions as well as for detection and classification of animals for biological and ecological applications. The studies involved measurements over the frequency range 24 kHz to 1 MHz and all angles of orientation in as small as 1° increments. This substantial data set is quite revealing of the physics of the acoustic scattering by these complex shelled bodies and served as a basis for the modeling. Specifically, the resonance structure of the scattering was strongly dependent upon angle of orientation and could be traced to various types of rays (e.g., subsonic Lamb waves and rays entering the opercular opening). The data are analyzed in both the frequency and time domain (compressed pulse processing) so that dominant scattering mechanisms could be identified. Given the complexity of the animal body (irregular elastic shell with discontinuities), approximate scattering models are used with only the dominant scattering properties retained. Two models are applied to the data, both approximating the body as a deformed sphere: (1) an averaged form of the exact modal-series-based solution for the spherical shell, which is used to estimate the backscattering by a deformed shell averaged over all angles of orientation, and produces reasonably accurate predictions over all k1aesr (k1 is the acoustic wave number of the surrounding water and aesr is the equivalent spherical radius of the body), and (2) a ray-based formula which is used to estimate the scattering at fixed angle of orientation, but only for high k1aesr. The ray-based model is an extension of a model recently developed for the shelled zooplankton Limacina retroversa that has a shape similar to that of the Littorina littorea but swims through the water [Stanton et al., J. Acoust. Soc. Am. 103, 236–253 (1998b)]. Applications of remote detection and classification of the seafloor and water column in the presence of shelled animals are discussed.
Description
Author Posting. © Acoustical Society of America, 2000. 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 108 (2000): 535-550, doi:10.1121/1.429584.
Collections
Suggested Citation
Journal of the Acoustical Society of America 108 (2000): 535-550Related items
Showing items related by title, author, creator and subject.
-
Differences between sound scattering by weakly scattering spheres and finite-length cylinders with applications to sound scattering by zooplankton
Stanton, Timothy K.; Wiebe, Peter H.; Chu, Dezhang (Acoustical Society of America, 1998-01)A modeling study was conducted to determine the conditions under which fluidlike zooplankton of the same volume but different shapes (spherical/cylindrical) have similar or dramatically different scattering properties. ... -
Broadband and statistical characterization of echoes from random scatterers : application to acoustic scattering by marine organisms
Lee, Wu-Jung (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 2013-02)The interpretation of echoes collected by active remote-sensing systems, such as sonar and radar, is often ambiguous due to the complexities in the scattering processes involving the scatterers, the environment, and the ... -
Sound scattering by several zooplankton groups. II. Scattering models
Stanton, Timothy K.; Chu, Dezhang; Wiebe, Peter H. (Acoustical Society of America, 1998-01)Mathematical scattering models are derived and compared with data from zooplankton from several gross anatomical groups—fluidlike, elastic shelled, and gas bearing. The models are based upon the acoustically inferred ...