Statistics of Distinct Clutter Classes in Midfrequency Active Sonar

Gelb, James M.; Heath, R. E.; Tipple, George L.

doi:10.1109/joe.2009.2031547

Cited by 28 publications

(23 citation statements)

References 26 publications

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“…Echoes from non-targets that have an envelope PDF with an elevated, high amplitude tail when compared with this distribution can be considered clutter. 36,37 Similarly, in scientific studies, deviations from the Rayleigh distribution contain important information on the scatterer of interest. 38 All echo envelope distributions modeled in this study are, therefore, compared with a Rayleigh distribution to measure the contribution of specific parameters toward any deviation from this benchmark.…”

Section: A Rayleigh Distributionmentioning

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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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: A Rayleigh Distributionmentioning

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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“…Both empirical analysis and theoretical models show that the K distribution can represent a wide variety of active sonar clutter over diverse frequencies and bandwidths. As might be expected, the best fits are observed when the data used in the estimation are statistically stationary, with the converse true as illustrated in [1], [2] where the K-distribution fit degraded as the data became subjectively less stationary or exceptionally heavy tailed. Analyzing data after normalization of the average power level can mitigate the non-stationarity induced by the decay in reverberation power level with range.…”

Section: Introductionmentioning

confidence: 60%

“…II is applied to a sample of the "compact non-stationary" class clutter data from [2] where it was described as being "distinct dense discrete clumps." The data are received on a mid-frequency sonar using a 200-Hz bandwidth hyperbolic-frequency-modulated transmit waveform and are beamformed, matched filtered, and normalized prior to the following P f a analysis.…”

Section: Real Datamentioning

confidence: 99%

K-Rayleigh mixture model for sparse active sonar clutter

Abraham

Gelb

Oldag

2010

Oceans'10 Ieee Sydney

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Abstract-The mixture of a Rayleigh probability density function (PDF) and a K PDF is proposed for representing active sonar data comprising clutter sparsely observed in a Rayleigh-distributed background. While both the Rayleigh and K distributions have been shown to accurately represent the statistics of certain types of active sonar data, it is common to observe data containing both echoes from distinct clutter objects and more diffuse, Rayleigh-distributed reverberation. While the K distribution can often still capture the behavior of such data, the K-Rayleigh mixture is seen to provide improved PDF fits and inference on the clutter statistics. A parameter estimation algorithm for the K-Rayleigh mixture PDF based on the expectation-maximization (EM) technique is proposed and shown to provide adequate performance in representing the PDF of very heavy tailed real sonar data.

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“…To help reduce the false alarm rate, several studies have been conducted to devise signalprocessing strategies to separate real from false targets based on temporal-spectral characteristics 20,21 and statistical analyses of the received time series. 9,10,22 In these latter studies sonar "clutter" is characterized by echoes that exceed a given threshold above the mean background level (sum of reverberation and noise), and are similar to those being measured. For example, since the temporal extent of an echo is related to the size of the scattering volume (coupled with propagation effects-e.g., see Ref.…”

Section: Introductionmentioning

confidence: 89%

“…This latter case has led to recent efforts to quantify the impacts of biologics as a source of interference on some mid-frequency systems. [9][10][11] A major limitation in most systems, to date, is that the sonars are narrowband-that is, they use signals whose bandwidth is about 10% of the center frequency. These narrowband systems have limited capability to classify scatterers in the spectral domain where unique scattering properties exist.…”

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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Statistics of Distinct Clutter Classes in Midfrequency Active Sonar

Cited by 28 publications

References 26 publications

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

K-Rayleigh mixture model for sparse active sonar clutter

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

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