Demonstration of the invariance principle for active sonar

Quijano, Jorge E.; Zurk, Lisa M.; Rouseff, Daniel

doi:10.1121/1.2836763

Cited by 33 publications

(29 citation statements)

References 12 publications

(7 reference statements)

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“…Using / ¼ 52 and / 0 ¼ 20 in Eq. (18) yields a value for the waveguide invariant b ¼ 1.3, a value consistent with experimental results 3,4 when both source and receiver are below the main thermocline.…”

Section: Introductionsupporting

confidence: 70%

“…The canonical value in shallow water is b ¼ 1, but this choice may prove far too coarse. If both the source and array are below the thermocline, both simulations 2 and experiments 3,4 have shown that b ¼ 1.3 or 1.4 is more appropriate. Erroneously assuming b ¼ 1 when it is actually b ¼ 1.3 translates directly into a 30% error in the estimated value for the range.…”

Section: Introductionmentioning

confidence: 99%

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Scintillation in a shallow water waveguide

Rouseff¹,

Zurk²

2012

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Section: Introductionsupporting

confidence: 70%

Section: Introductionmentioning

confidence: 99%

Scintillation in a shallow water waveguide

Rouseff¹,

Zurk²

2012

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“…In most shallow water environments, b is roughly constant with a value close to 1. The apparent simplicity of the WI gave rise to an exhaustive set of applications (passive localization, 9,10 geo-acoustics inversion, 11 active sonar, 12,13 source separation, 14 dispersion compensation 15,16 ). On the other hand, Baggeroer 17 and Rouseff and Spindel 18 simultaneously reminded that considering the WI as a constant is not realistic for stratified SSPs, where refraction becomes non-negligible.…”

Section: Introductionmentioning

confidence: 99%

“…This idea is mentioned in several papers 3,4,12 but it has never been introduce directly in a derivation of E b . Second, we derive the WI from Eq.…”

mentioning

confidence: 99%

Understanding deep-water striation patterns and predicting the waveguide invariant as a distribution depending on range and depth

Emmetière

Bonnel

Gehant

et al. 2018

The Journal of the Acoustical Society of America

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The Waveguide Invariant (WI) theory has been introduced to quantify the orientation of the intensity interference patterns in a range-frequency domain. When the sound speed is constant over the water column, the WI is a scalar with the canonical value of 1. But, when considering shallow waters with a stratified sound speed profile, the WI ceases to be constant and is more appropriately described by a distribution, which is mainly sensitive to source/receiver depths. Such configurations have been widely investigated, with practical applications including passive source localization. However, in deep waters, the interference pattern is much more complex and variable. In fact the observed WI varies with source/receiver depth but it also varies very quickly with source-array range. In this paper, the authors investigate two phenomena responsible for this variability, namely the dominance of the acoustic field by groups of modes and the frequency dependence of the eigenmodes. Using a ray-mode approach, these two features are integrated in a WI distribution derivation. Their importance in deep-water is validated by testing the calculated WI distribution against a reference distribution directly measured on synthetic data. The proposed WI derivation provides a thorough way to predict and understand the striation patterns in deep-water context.

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“…The waveguide invariant has been used for a wide range of applications such as: passive range estimation [58,56,62], matched field processing [59,23], active sonar [49,27,25], array processing [37,57,66], time-reversal mirrors [32,54,38,39], and more (See Appendix A for a complete review of the waveguide invari-ant literature). Despite its many uses, the waveguide invariant is not well studied compared to other ocean-acoustic phenomena.…”

Section: Introductionmentioning

confidence: 99%

Understanding and utilizing waveguide invariant range-frequency striations in ocean acoustic waveguides

Cockrell¹

2011

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Much of the recent research in ocean acoustics has focused on developing methods to exploit the effects that the sea surface and seafloor have on acoustic propagation. Many of those methods require detailed knowledge of the acoustic properties of the seafloor and the sound speed profile (SSP), which limits their applicability. The range-frequency waveguide invariant describes striations that often appear in plots of acoustic intensity versus range and frequency. These range-frequency striations have properties that depend strongly on the frequency of the acoustic source and on distance between the acoustic source and receiver, but that depend mildly on the SSP and seafloor properties. Because of this dependence, the waveguide invariant can be utilized for applications such as passive and active sonar, time-reversal mirrors, and array processing, even when the SSP or the seafloor properties are not well known. This thesis develops a framework for understanding and calculating the waveguide invariant, and uses that framework to develop signal processing techniques for the waveguide invariant.A method for passively estimating the range from an acoustic source to a receiver is developed, and tested on experimental data. Heuristics are developed to estimate the minimum source bandwidth and minimum horizontal aperture required for range estimation.A semi-analytic formula for the waveguide invariant is derived using WKB approximation along with a normal mode description of the acoustic field in a rangeindependent waveguide. This formula is applicable to waveguides with arbitrary SSPs, and reveals precisely how the SSP and the seafloor reflection coefficient affect the value of the waveguide invariant.Previous research has shown that the waveguide invariant range-frequency striations can be observed using a single hydrophone or a horizontal line array (HLA) of hydrophones. This thesis shows that traditional array processing techniques are sometimes inadequate for the purpose of observing range-frequency striations using a HLA. Array processing techniques designed specifically for observing range-3 frequency striations are developed and demonstrated.Finally, a relationship between the waveguide invariant and wavenumber integrations is derived, which may be useful for studying range-frequency striations in elastic environments such as ice-covered waveguides.

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Demonstration of the invariance principle for active sonar

Cited by 33 publications

References 12 publications

Scintillation in a shallow water waveguide

Scintillation in a shallow water waveguide

Understanding deep-water striation patterns and predicting the waveguide invariant as a distribution depending on range and depth

Understanding and utilizing waveguide invariant range-frequency striations in ocean acoustic waveguides

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