Ocean Acoustics, Matched-Field Processing and Phase Conjugation

Kuperman, W. A.; Jackson, D.R.

doi:10.1007/3-540-44680-x_3

Cited by 25 publications

(19 citation statements)

References 36 publications

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“…For data taken near Nantucket, 30 bE GM was estimated to be 0.5 m. 28 For data taken on the New England shelf during the 1996 Coastal Mixing and Optics Experiment, 31 bE GM = 0.35 m. 32,33 . For data taken in a less energetic internal wave field in the Mediterranean, bE GM = 0.135 m. 34 In the model/data comparisons of Sec. III, bE GM will be treated as the lone adjustable parameter.…”

Section: ͑22͒mentioning

confidence: 99%

Internal wave effects on the ambient noise notch in the East China Sea: Model/data comparison

Rouseff

Tang

2006

The Journal of the Acoustical Society of America

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The vertical directivity pattern of the ambient noise field observed in shallow water is typically anisotropic with a trough in the horizontal. This trough, often called the ambient noise notch, develops because downward refraction steepens all rays emanating from near the sea surface. Variability in the environment has the potential to redistribute the noise into shallower angles and thereby fill the notch. In the present work, a model for the width and depth of the ambient noise notch is developed. Transport theory for acoustic propagation is combined with a shallow water internal wave model to predict the average output of a beamformer. Ambient noise data from the East China Sea are analyzed in the 1-to-5-kHz band. Good agreement between the model and the data for both the width and depth of the ambient noise notch is obtained at multiple frequencies, suggesting that internal wave effects are significant.

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Section: ͑22͒mentioning

confidence: 99%

Internal wave effects on the ambient noise notch in the East China Sea: Model/data comparison

Rouseff

Tang

2006

The Journal of the Acoustical Society of America

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“…Another use of time-reversal is related with compensation for distortions, caused by multipath and unknown antenna array deformation, which limit the capacity of underwater communications [47][48][49][50][51][52][53][54][55][56][57][58][59][60][61][62][63][64][65][66]. Furthermore, time-reversal can confine acoustic energy to a narrow beam that will track the intended receiver [47], called spatial focusing.…”

Section: Time-reversal-a Reviewmentioning

confidence: 99%

Time-Reversal for UWB Communications Systems

Qiu¹

2005

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“…The first term is twice the Green's function in a homogeneous space G 0 (r) = ρ exp(ikr)/4πr. While at the source (r = 0) this Green's function is singular, the imaginary part of this Green's function, given by Im (G 0 (r)) = ρ sin(kr)/4πr, tends to the finite value ρk/4π as r → 0 [47]. For the layer model, the imaginary component of the Green's function is given by This function, normalized to the corresponding value Im (G 0 (0, 0)) = ρk/4π for the freespace Green's function, is shown in Figure 1 as a function of normalized frequency f τ , where τ = 2h/c is the two-way vertical travel time in the layer.…”

mentioning

confidence: 99%

Field Fluctuations, Imaging with Backscattered Waves, a Generalized Energy Theorem, and the Optical Theorem

Snieder¹,

Sánchez‐Sesma²,

Wapenaar³

2009

SIAM J. Imaging Sci.

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We show the connection between four aspects of wave propagation: the autocorrelation of field fluctuations, imaging with backscattered waves, a theorem for energy flow, and the generalized optical theorem. The autocorrelation of field fluctuations can be used to extract the imaginary component of the Green's function at the source. The Green's function usually is singular at the source, but the imaginary component is not. The imaginary component of the Green's function at the source can thus be retrieved from the autocorrelation of field fluctuations, and can be used to image the medium using backscattered fields. We also show for general linear systems, which may be open or closed and may be dissipative, that the imaginary component of the Green's function at the source accounts for the loss of generalized energy by dissipation and/or propagation of the fields away from the source. Finally we show that the expressions for the extraction of the Green's function for scalar waves has the same mathematical structure as the generalized optical theorem. The theory presented here is shown to be applicable to damped acoustic waves, quantum mechanics, and diffusion.

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Ocean Acoustics, Matched-Field Processing and Phase Conjugation

Cited by 25 publications

References 36 publications

Internal wave effects on the ambient noise notch in the East China Sea: Model/data comparison

Internal wave effects on the ambient noise notch in the East China Sea: Model/data comparison

Time-Reversal for UWB Communications Systems

Field Fluctuations, Imaging with Backscattered Waves, a Generalized Energy Theorem, and the Optical Theorem

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