Coupled mode transport theory for sound transmission through an ocean with random sound speed perturbations: Coherence in deep water environments
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Authors
Colosi, John A.
Chandrayadula, Tarun K.
Voronovich, Alexander G.
Ostashev, Vladimir E.
Subjects
Advisors
Date of Issue
2013-10
Date
October 2013
Publisher
Language
Abstract
Second moments of mode amplitudes at fixed frequency as a function of separations in mode number,
time, and horizontal distance are investigated using mode-based transport equations and Monte
Carlo simulation. These second moments are used to study full-field acoustic coherence, including
depth separations. Calculations for low-order modes between 50 and 250 Hz are presented using a
deep-water Philippine Sea environment. Comparisons between Monte Carlo simulations and transport
theory for time and depth coherence at frequencies of 75 and 250 Hz and for ranges up to
500 km show good agreement. The theory is used to examine the accuracy of the adiabatic and
quadratic lag approximations, and the range and frequency scaling of coherence. It is found that
while temporal coherence has a dominant adiabatic component, horizontal and vertical coherence
have more equal contributions from coupling and adiabatic effects. In addition, the quadratic lag
approximation is shown to be most accurate at higher frequencies and longer ranges. Last the
range and frequency scalings are found to be sensitive to the functional form of the exponential
decay of coherence with lag, but temporal and horizontal coherence show scalings that
fall quite close to the well-known inverse frequency and inverse square root range laws.
Type
Article
Description
The article of record as published may be found at http://dx.doi.org/10.1121/1.4818779
Series/Report No
Department
Oceanography
Organization
Naval Postgraduate School (U.S.)
Identifiers
NPS Report Number
Sponsors
Office of Naval Research Ocean Acoustics Program Code (322)
Funder
Office of Naval Research Ocean Acoustics Program Code (322)
Format
15 p.
Citation
J. Acoust. Soc. Am. Vol. 134 (4), Pt. 2 (October 2013), p. 3119-3133
Distribution Statement
Rights
This publication is a work of the U.S. Government as defined in Title 17, United States Code, Section 101. Copyright protection is not available for this work in the United States.