Spatial coherence in range‐dependent shallow water environments

1998 ◽  
Vol 103 (5) ◽  
pp. 2856-2856
Author(s):  
Ilya Rozenfeld ◽  
William M. Carey ◽  
James F. Lynch ◽  
Peter Cable ◽  
William L. Siegmann
Keyword(s):  
Shallow Water ◽  
Spatial Coherence

Spatial coherence measurements from two L-shape arrays in Shallow Water

2009 ◽  
Vol 55 (3) ◽  
pp. 383-392 ◽  
Author(s):  
Lin Wan ◽  
Ji-Xun Zhou ◽  
Peter H. Rogers ◽  
David P. Knobles
Keyword(s):  
Shallow Water ◽  
Spatial Coherence

Effects of random bottom bathymetry on temporal and spatial coherence in shallow water propagation

2011 ◽  
Vol 130 (4) ◽  
pp. 2349-2349
Author(s):  
Jennifer Wylie ◽  
Felipe Lourenco ◽  
Harry DeFerrari
Keyword(s):  
Shallow Water ◽  
Spatial Coherence ◽  
Temporal And Spatial

Spatial coherence in shallow water

2002 ◽  
Author(s):  
I. Rozenfeld ◽  
P. Cable ◽  
W.M. Carey ◽  
W.L. Siegmann
Keyword(s):  
Shallow Water ◽  
Spatial Coherence

scholarly journals Transverse horizontal spatial coherence in shallow water

2019 ◽  
Vol 283 ◽  
pp. 02001
Author(s):  
Bo Zhang ◽  
Fenghua Li ◽  
Zhenglin Li ◽  
Yanjun Zhang ◽  
Jingyan Wang
Keyword(s):  
Shallow Water ◽  
Acoustical Society ◽  
Coherence Length ◽  
Environmental Variability ◽  
Northern South China Sea ◽  
Spatial Coherence ◽  
Normal Modes ◽  
Sound Field ◽  
Acoustic Frequency ◽  
Field Correlation

Since the advent of large-aperture array processing, more and more attention has been paid to the sound field correlation, which has fundamental limit to the array gain of spatial coherent signal processing. The two dominant mechanisms that degrade the spatial coherence are normal modes (or multi-paths) interference and the environmental variability caused by several relevant oceanographic processes. In the present study, the transverse horizontal spatial coherence of explosive signals has been studied experimentally by a bottom-mounted array in the Northern South China Sea. And the effects of normal mode interference on the transverse horizontal spatial coherence have been analyzed numerically. Expressed in terms of wavelengths, the coherence length is shown to be larger than 170λ/185λ at acoustic frequency 508-640Hz/80-101Hz in shallow water. It is much greater than Carey’s shallow-water result 30λ estimated from array signal gain after assuming a specific functional form for the coherence (The Journal of the Acoustical Society of America 104, 831 (1998)). It, however, is consistent with Rouseff’s modelling result of a coherence length larger than 100λ (The Journal of the Acoustical Society of America 138, 2256 (2015)). Both Carey and Rouseff argue that the transverse horizontal spatial coherence length depends only weakly on range, in direct. In the present study, however, the coherence length is shown to depend highly on source-receiver range, and it fluctuates synchronously with the sound-field intensity while range varies.

SOUND TRANSMISSION AND SPATIAL COHERENCE IN SELECTED SHALLOW-WATER AREAS: MEASUREMENTS AND THEORY

2006 ◽  
Vol 14 (02) ◽  
pp. 265-298 ◽  
Author(s):  
WILLIAM M. CAREY ◽  
JAMES F. LYNCH ◽  
WILLIAM L. SIEGMANN ◽  
ILYA ROZENFELD ◽  
BRIAN J. SPERRY
Keyword(s):  
Shallow Water ◽  
Coherence Function ◽  
Spatial Coherence ◽  
Normal Modes ◽  
Sound Transmission ◽  
Dominant Factor ◽  
Water Volume ◽  
Oceanic Water ◽  
Coherence Lengths ◽  
Loss Of Coherence

Experiments from several shallow-water areas are summarized. Coherent sound transmission results, particularly wavenumber spectra, are compared to range-dependent calculations that use oceanographic and geophysical characteristics from measurements and archives as bounded inputs to the propagation codes. In general excellent agreement was obtained between the measured and calculated results for both narrowband and broadband transmissions between 50 Hz and 1 kHz to ranges of 40 km. A relative signal gain (RSG) method for the estimation of horizontal coherence length was applied to measured RSG results and yielded coherence lengths on the order of 30λ at 400 Hz at distances of 40 km. Perturbation theory was applied to the shallow-water waveguide under the condition of adiabatic normal modes and expressions were derived for the phase structure function that was simplified by the use of Gaussian correlation functions. These analytical results, along with estimates of the variances of the environmental variables permitted the estimation of the coherence function and the RSG. The calculated coherence function and RSG were found to be consistent with measured RSG and replica correlation results. The fluctuations in the oceanic water volume were found to be the dominant factor in the loss of coherence.

Effect of Sub-Bottom Inhomogenieties on Shallow Water Spatial Coherence

1986 ◽  
pp. 397-405 ◽  
Author(s):  
S. T. McDaniel ◽  
D. F. McCammon
Keyword(s):  
Shallow Water ◽  
Spatial Coherence
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