Fish echoes on a long-range sonar display

Weston, D. E.; Revie, J.

doi:10.1016/0022-460x(71)90139-8

Cited by 28 publications

(11 citation statements)

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“…An understanding of how this complex environment affects echo statistics can aid operators in predicting sonar performance, lead to more realistic simulations for use in training sonar operators, and help researchers develop automated discriminators that could filter clutter (i.e., non-target echoes) from echoes of interest in sonar data. In addition to military applications, the interpretation of echoes from aggregations of scatterers observed on horizontal-looking sonar systems has applications to biologic surveys, [1][2][3][4][5][6] where species discrimination and abundance estimation are of interest. Understanding the acoustic response of each of the various complexities that exist in shallow water is crucial to predicting and interpreting echo statistics in these regions.…”

Section: Introductionmentioning

confidence: 99%

“…The waveguide is characterized by many factors that can be subdivided into deterministic and stochastic factors. To first order, the deterministic factors affecting the echo statistics are: (1) The average water column sound-speed profile (SSP) and (2) large-scale bathymetric features. Stochastic factors can include (1) sound-speed perturbations in the water column [such as those caused by internal waves (IWs)], (2) small-scale bottom roughness, and (3) surface roughness.…”

Section: Introductionmentioning

confidence: 99%

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Echo statistics of individual and aggregations of scatterers in the water column of a random, oceanic waveguide

Jones

Colosi

Stanton

2014

The Journal of the Acoustical Society of America

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The relative contributions of various physical factors to producing non-Rayleigh distributions of echo magnitudes in a waveguide are examined. Factors that are considered include (1) a stochastic, range-dependent sound-speed profile, (2) a directional acoustic source, (3) a variable scattering response, and (4) an extended scattering volume. A two-way parabolic equation model, coupled with a stochastic internal wave model, produces realistic simulations of acoustic propagation through a complex oceanic sound speed field. Simulations are conducted for a single frequency (3 kHz), monostatic sonar with a narrow beam (5 À3 dB beam width). The randomization of the waveguide, range of propagation, directionality of the sonar, and spatial extent of the scatterers each contribute to the degree to which the echo statistics are non-Rayleigh. Of critical importance are the deterministic and stochastic processes that induce multipath and drive the one-way acoustic pressure field to saturation (i.e., complex-Gaussian statistics). In this limit predictable statistics of echo envelopes are obtained at all ranges. A computationally low-budget phasor summation can successfully predict the probability density functions when the beam pattern and number of scatterers ensonified are known quantities. [http://dx

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Echo statistics of individual and aggregations of scatterers in the water column of a random, oceanic waveguide

Jones

Colosi

Stanton

2014

The Journal of the Acoustical Society of America

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“…J. S. M. Rusby later confirmed the fish backscattering in 1971 using a towedarray system to explore a Scottish inshore herring fishery. 4 Acoustical processing has matured since then. Advances in modeling the way sound propagates and scatters in a fluctuating, range-dependent waveguide and better signal processing methods are largely what separate Makris's relatively high-resolution images of fish population density from the pioneering efforts of Weston and Rusby.…”

Section: Runs For 24 Hours On 2 Aa Batteriesmentioning

confidence: 99%

Acoustic-waveguide sonar finds enormous fish shoals

Wilson¹

2006

Physics Today

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“…[1][2][3][4] Such long-range systems, which typically have detection ranges much greater than the water depth, have distinct advantages over conventional downward-looking echosounders as they can rapidly capture the high degree of spatio-temporal variability of fish over large areas. However, only a few studies have attempted to quantify distributions of fish using longrange systems.…”

Section: Introductionmentioning

confidence: 99%

“…5,6,12 Fisheries applications (i.e., fish finding sonar) typically involve ranges of hundreds of meters to 1 km, 13,14 but can extend to 30-50 km. 2,15 A strength of these systems is that they can be used to rapidly survey large volumes of water enabling researchers to measure fish populations even when the fish are sparsely distributed (i.e., separated in space more widely than the typical beamwidth of a downward looking echosounder). However, complications arise when trying to interpret echoes from widely distributed sources because complementary data are difficult to obtain.…”

Section: Introductionmentioning

confidence: 99%

Broadband classification and statistics of echoes from aggregations of fish measured by long-range, mid-frequency sonar

Jones

Stanton

Colosi

et al. 2017

The Journal of the Acoustical Society of America

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For horizontal-looking sonar systems operating at mid-frequencies (1–10 kHz), scattering by fish with resonant gas-filled swimbladders can dominate seafloor and surface reverberation at long-ranges (i.e., distances much greater than the water depth). This source of scattering, which can be difficult to distinguish from other sources of scattering in the water column or at the boundaries, can add spatio-temporal variability to an already complex acoustic record. Sparsely distributed, spatially compact fish aggregations were measured in the Gulf of Maine using a long-range broadband sonar with continuous spectral coverage from 1.5 to 5 kHz. Observed echoes, that are at least 15 decibels above background levels in the horizontal-looking sonar data, are classified spectrally by the resonance features as due to swimbladder-bearing fish. Contemporaneous multi-frequency echosounder measurements (18, 38, and 120 kHz) and net samples are used in conjunction with physics-based acoustic models to validate this approach. Furthermore, the fish aggregations are statistically characterized in the long-range data by highly non-Rayleigh distributions of the echo magnitudes. These distributions are accurately predicted by a computationally efficient, physics-based model. The model accounts for beam-pattern and waveguide effects as well as the scattering response of aggregations of fish.

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Fish echoes on a long-range sonar display

Cited by 28 publications

References 1 publication

Echo statistics of individual and aggregations of scatterers in the water column of a random, oceanic waveguide

Echo statistics of individual and aggregations of scatterers in the water column of a random, oceanic waveguide

Acoustic-waveguide sonar finds enormous fish shoals

Broadband classification and statistics of echoes from aggregations of fish measured by long-range, mid-frequency sonar

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