Sound scattering by several zooplankton groups. I. Experimental determination of dominant scattering mechanisms


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dc.contributor.author Stanton, Timothy K.
dc.contributor.author Chu, Dezhang
dc.contributor.author Wiebe, Peter H.
dc.contributor.author Martin, Linda V.
dc.contributor.author Eastwood, Robert L.
dc.date.accessioned 2008-10-21T13:36:08Z
dc.date.available 2008-10-21T13:36:08Z
dc.date.issued 1998-01
dc.identifier.citation Journal of the Acoustical Society of America 103 (1998): 225-235 en
dc.identifier.uri http://hdl.handle.net/1912/2514
dc.description Author Posting. © Acoustical Society of America, 1998. 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 103 (1998): 225-235, doi:10.1121/1.421469. en
dc.description.abstract The acoustic scattering properties of live individual zooplankton from several gross anatomical groups have been investigated. The groups involve (1) euphausiids (Meganyctiphanes norvegica) whose bodies behave acoustically as a fluid material, (2) gastropods (Limacina retroversa) whose bodies include a hard elastic shell, and (3) siphonophores (Agalma okeni or elegans and Nanomia cara) whose bodies contain a gas inclusion (pneumatophore). The animals were collected from ocean waters off New England (Slope Water, Georges Bank, and the Gulf of Maine). The scattering properties were measured over parts or all of the frequency range 50 kHz to 1 MHz in a laboratory-style pulse-echo setup in a large tank at sea using live fresh specimens. Individual echoes as well as averages and ping-to-ping fluctuations of repeated echoes were studied. The material type of each group is shown to strongly affect both the overall echo level and pattern of the target strength versus frequency plots. In this first article of a two-part series, the dominant scattering mechanisms of the three animal types are determined principally by examining the structure of both the frequency spectra of individual broadband echoes and the compressed pulse (time series) output. Other information is also used involving the effect on overall levels due to (1) animal orientation and (2) tissue in animals having a gas inclusion (siphonophores). The results of this first paper show that (1) the euphausiids behave as weakly scattering fluid bodies and there are major contributions from at least two parts of the body to the echo (the number of contributions depends upon angle of orientation and shape), (2) the gastropods produce echoes from the front interface and possibly from a slow-traveling circumferential (Lamb) wave, and (3) the gas inclusion of the siphonophore dominates the echoes, but the tissue plays a role in the scattering and is especially important when analyzing echoes from individual animals on a ping-by-ping basis. The results of this paper serve as the basis for the development of acoustic scattering models in the companion paper [Stanton et al., J. Acoust. Soc. Am. 103, 236–253 (1998)]. en
dc.description.sponsorship This work was supported by the National Science Foundation Grant No. OCE- 9201264, the U.S. Office of Naval Research Grant Nos. N00014-89-J-1729 and N00014-95-1-0287, and the MIT/ WHOI Joint Graduate Education Program. en
dc.format.mimetype application/pdf
dc.language.iso en_US en
dc.publisher Acoustical Society of America en
dc.relation.uri http://dx.doi.org/10.1121/1.421469
dc.subject Bioacoustics en
dc.subject Acoustic wave scattering en
dc.subject Fluctuations en
dc.title Sound scattering by several zooplankton groups. I. Experimental determination of dominant scattering mechanisms en
dc.type Article en
dc.identifier.doi 10.1121/1.421469

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