J Acoust Soc Am 2012 Feb;131(2):1749-61

Department of Oceanography, Naval Postgraduate School Monterey, California 93943, USA.

Second- and fourth-moment mode-amplitude statistics for low-frequency ocean sound propagation through random sound-speed perturbations in a shallow-water environment are investigated using Monte Carlo simulations and a transport theory for the cross-mode coherence matrix. The acoustic observables of mean and mean square intensity are presented and the importance of adiabatic effects and cross-mode coherence decay are emphasized. Using frequencies of 200 and 400 Hz, transport theory is compared with Monte Carlo simulations in a canonical shallow-water environment representative of the summer Mid-Atlantic Bight. Except for ranges less than a horizontal coherence length of the sound structure, the intensity moments from the two calculations are in good agreement. Corrections for the short range behavior are presented. For these frequencies the computed mode coupling rates are extremely small, and the propagation is strongly adiabatic with a rapid decay of cross-mode coherence. Coupling effects are predicted to be important at kilohertz frequencies. Decay of cross-mode coherence has important implications for acoustic interactions with nonlinear internal waves: For the case in which the acoustic path is not at glancing incidence with a nonlinear internal-wave front, adiabatic phase randomizing effects lead to a significantly reduced influence of the nonlinear waves on both mean and mean square intensity.

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J Acoust Soc Am 2015 May;137(5):2950-61

Oceanography Department, Naval Postgraduate School, Monterey, California 93943, USA.

In an earlier article, the statistical properties of mode propagation were studied at a frequency of 1 kHz in a shallow water environment with random sound-speed perturbations from linear internal waves, using a hybrid transport theory and Monte Carlo numerical simulations. Here, the analysis is extended to include the effects of random linear surface waves, in isolation and in combination with internal waves. Mode coupling rates for both surface and internal waves are found to be significant, but strongly dependent on mode number. Read More

J Acoust Soc Am 2013 Oct;134(4):3144-60

Naval Postgraduate School, Monterey, California 93943.

Second order mode statistics as a function of range and source depth are presented from the Long Range Ocean Acoustic Propagation EXperiment (LOAPEX). During LOAPEX, low frequency broadband signals were transmitted from a ship-suspended source to a mode-resolving vertical line array. Over a one-month period, the ship occupied seven stations from 50 km to 3200 km distance from the receiver. Read More

J Acoust Soc Am 2012 Feb;131(2):1749-61

Department of Oceanography, Naval Postgraduate School Monterey, California 93943, USA.

Second- and fourth-moment mode-amplitude statistics for low-frequency ocean sound propagation through random sound-speed perturbations in a shallow-water environment are investigated using Monte Carlo simulations and a transport theory for the cross-mode coherence matrix. The acoustic observables of mean and mean square intensity are presented and the importance of adiabatic effects and cross-mode coherence decay are emphasized. Using frequencies of 200 and 400 Hz, transport theory is compared with Monte Carlo simulations in a canonical shallow-water environment representative of the summer Mid-Atlantic Bight. Read More

J Acoust Soc Am 2009 Sep;126(3):1026-35

Department of Oceanography, Naval Postgraduate School, Monterey, CA 93943, USA.

In this paper Creamer's [(1996). J. Acoust. Read More

Opt Express 2007 Sep;15(18):11731-40

We demonstrate that fiber lasers spectrally broadened by cross mode coupling can be coherently combined with high efficiency. The spectral broadening that it induces suppresses stimulated Brillouin scattering. Using long cavity length lasers, > 800 m, we induce spectral broadening of > 50 GHz and show mode by mode coherence in the output of four intracavity coupled fiber lasers. Read More