Average echoes from randomly oriented random-length finite cylinders : zooplankton models
Stanton, Timothy K.
Wiebe, Peter H.
Clay, Clarence S.
MetadataShow full item record
By heuristically extending the previously developed ray solution [Stanton et al. J. Acoust. Soc. Am. 94, 3454–3462 (1993)] to predict the scattering by cylinders over all angles of incidence, approximate expressions are derived which describe the echo energy due to sound scattered by finite cylinders averaged over orientation and length. Both straight and bent finite length cylinders of high aspect ratio are considered over the full range of frequencies (Rayleigh through geometric scattering). The results show that for a sufficiently broad range of orientation, the average echo is largely independent of the degree of bend—that is, the results are essentially the same for both the straight and bent cylinders of various radii of curvature (provided the bend is not too great). Also, in the limit of high frequency (i.e., the acoustic wavelength is much smaller than the cross-sectional radius of the object), the averages are independent of frequency. The resultant formulas derived herein are useful in describing the scattering by elongated zooplankton whose shape may not necessarily be known in the natural ocean environment. The average echo is shown to depend directly upon standard deviation (s.d.) of the angle of orientation as well as size. If independent measurements of size are made (such as from trawling samples), then the properties of the angle distribution and hence behavior may be inferred from the data. Averages over both angle and a narrow distribution of size are shown to only partially smooth out deep nulls in the scatter versus frequency curves. The formulas compare favorably with laboratory data involving aggregations of animals and a broad range of frequencies (38 kHz to 1.2 MHz).
Author Posting. © Acoustical Society of America, 1993. 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 94 (1993): 3463-3472, doi:10.1121/1.407200.
Showing items related by title, author, creator and subject.
Goda, Makoto; Inoue, Shinya; Mabuchi, Issei (Marine Biological Laboratory, 2009-02)Calyculin-A (CLA), a protein phosphatase inhibitor, has been known to induce cleavage resembling normal furrowing in unfertilized sea urchin eggs. In CLA-treated eggs, actin filaments and myosin assemble to form a contractile ...
Statistics of normal mode amplitudes in an ocean with random sound-speed perturbations : cross-mode coherence and mean intensity Colosi, John A.; Morozov, Andrey K. (Acoustical Society of America, 2009-09)In this paper Creamer's [(1996). J. Acoust. Soc. Am. 99, 2825–2838] transport equation for the mode amplitude coherence matrix resulting from coupled mode propagation through random fields of internal waves is examined in ...
Rodenbusch, George (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 1978-08)A linearized theory for the response of a circular pendulum spar in 2-dimensional waves and a uniform current is developed. The linear forces on the cylinder are predicted using an approximate potential flow theory for ...