Extracting the local Green’s function on a horizontal array from ambient ocean noise

Fried, Stephanie; Kuperman, W. A.; Sabra, Karim G.; Roux, Philippe

doi:10.1121/1.2960937

Cited by 39 publications

(50 citation statements)

References 10 publications

(7 reference statements)

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“…Compared to well-established seismic interferometry [Wapenaar et al, 2008], passive ocean acoustic tomography faces a number of unique challenges, including time-dependence of the environment, motion of receivers and the medium, and requirements of very high relative accuracy of measurements of the sound speed in water. While coherent wavefronts have been identified in noise cross-correlations [Roux et al, 2004;Fried et al, 2008;Brooks and Gerstoft, 2009], and noise interferometry is successfully used to study the ocean bottom [Siderius et al, 2010], no applications of the technique to quantitative characterization of the water column have been reported to date.…”

Section: Introductionmentioning

confidence: 99%

Ocean tomography with acoustic daylight

Godin

Zabotin

Goncharov

2010

Geophysical Research Letters

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Ambient noise in the ocean provides acoustic illumination, which can be used, similarly to daylight in the atmosphere, to visualize objects and characterize the environment. It has been shown theoretically that deterministic travel times between any two points in a moving or motionless, inhomogeneous, time‐independent medium can be retrieved from the cross‐correlation function of diffuse acoustic noise recorded at the two points, without a detailed knowledge of the noise field's sources or properties. In this paper, techniques are developed to account for receiver motion and suppress contributions due to powerful transient localized noise sources, such as nearby shipping, in order to enhance noise diffusivity. The data‐processing techniques are applied to ambient noise recordings of opportunity, which were obtained as a by‐product of a long‐range sound propagation experiment in the Pacific Ocean. The feasibility of passive ocean acoustic tomography with ambient noise recorded at two vertical line arrays is demonstrated successfully.

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Section: Introductionmentioning

confidence: 99%

Ocean tomography with acoustic daylight

Godin

Zabotin

Goncharov

2010

Geophysical Research Letters

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“…2(b)] yields a signature consistent with the coherent multipath structure experimentally observed between horizontal sensors. 17,18 For this feature the applied filter F ðkÞ was taken to be unity for all values of wavenumber. As all other components are assumed to arise from distant processes, they have been calculated such that the contribution from the wavenumber continuum has been removed, thus suppressing vertical components that are inconsistent with distant sources (see discussion in Sec.…”

Section: Arbitrary Horizontal Directivitymentioning

confidence: 99%

A model for the spatial coherence of arbitrarily directive noise in the depth-stratified ocean

Walker

2012

The Journal of the Acoustical Society of America

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Though referred to as noise, the ambient ocean soundscape carries valuable information about the physical ocean environment.To study this information, Kuperman and Ingenito introduced a model for spatial coherence in a depth stratified ocean arising from the vertically directive diffuse acoustic noise produced by bubbles distributed throughout the surface. Here the model is adapted to incorporate horizontal directivity as well, making it possible to include additional noise contributions from directive features such as storms, biologics, shipping, and wave breaking. As an analytic approach, the model can serve as a computationally light complement to existing methods.

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“…There are a number of ways of collecting a large amount of OAN. It is shown that large averaging of the NCF is needed for the better estimation of the GF if the noise is recorded at two hydrophones [8,10,[12][13][14][15][16]. But this takes long recording time.…”

Section: Introductionmentioning

confidence: 99%

“…The estimate in the passive fathometer is based on the extraction of the Green's Function (GF) from the ambient Noise Crosscorrelation Function (NCF) [2]. The GF between two points can be extracted from the derivative of the crosscorrelation between the Ocean Ambient Noise (OAN) received at those two points [6][7][8]. The better the estimate of the GF, the better the estimate in the passive fathometer.…”

Section: Introductionmentioning

confidence: 99%

Effect of Biological Activity on Broadband Passive Fathometry

Alam¹,

Huntington²,

Frater³

2013

OJA

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A passive fathometer can be formed by two vertically separated hydrophones. The depth can be estimated from the Green's function between the hydrophones, which is calculated from the cross-correlation between ocean ambient noise fields received at those two hydrophones. The performance of the fathometer depends on the signal to noise ratio (SNR) and the resolution of the noise cross-correlation function. In a given environment, improved SNR and resolution of the cross-correlation function can be achieved through longer observations, more observation points, or increasing bandwidth. Long time averaging has been demonstrated, but requires that the channel be stationary over the averaging time. Hydrophone arrays are commonly used, but result in increased cost and complexity. Recent work shows that the SNR and resolution of the correlation function can also be improved by the use of the large bandwidth noise fields. This paper shows that the non-surface biological noise generated by marine animals, such as shrimp, is one of the major issues in the performance of such a broadband passive fathometer operating in shallow water. This noise tends to occur at higher frequencies. Frequencies at which significant non-surface biological noise is present cannot be used to improve fathometer performance. Consequently, the upper limit of frequencies that can be used in a passive fathometer is limited by the lower limit of the bandwidth occupied by the biological noise.

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Extracting the local Green’s function on a horizontal array from ambient ocean noise

Cited by 39 publications

References 10 publications

Ocean tomography with acoustic daylight

Ocean tomography with acoustic daylight

A model for the spatial coherence of arbitrarily directive noise in the depth-stratified ocean

Effect of Biological Activity on Broadband Passive Fathometry

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