Statistics of low-frequency normal-mode amplitudes in an ocean with random sound-speed perturbations : shallow-water environments
MetadataShow full item record
KeywordMonte Carlo methods; Perturbation techniques; Seawater; Short-range order; Statistics; Underwater acoustic propagation
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.
Author Posting. © Acoustical Society 2012. This article is posted here by permission of Acoustical Society of America for personal use, not for redistribution. The definitive version was published in Journal of the Acoustical Society of America 131 (2012): 1749-1761, doi:10.1121/1.3666002.
Suggested CitationArticle: Colosi, John A., Duda, Timothy F., Morozov, Andrey K., "Statistics of low-frequency normal-mode amplitudes in an ocean with random sound-speed perturbations : shallow-water environments", Journal of the Acoustical Society of America 131 (2012): 1749-1761, DOI:10.1121/1.3666002, https://hdl.handle.net/1912/5091
Showing items related by title, author, creator and subject.
Statistics of normal mode amplitudes in an ocean with random sound-speed perturbations : cross-mode coherence and mean intensity Colosi, John A.; Morozov, Andrey K. (Acoustical Society of America, 2009-09)In this paper Creamer's [(1996). J. Acoust. Soc. Am. 99, 2825–2838] transport equation for the mode amplitude coherence matrix resulting from coupled mode propagation through random fields of internal waves is examined in ...
Duda, Timothy F. (Sears Foundation for Marine Research, 2017-05-01)Modeling acoustic conditions in an oceanic environment is a multiple-step process. The environmental conditions (features) in the area first must be measured or estimated; relevant features include seabed geometry, seabed ...
Horizontal coherence of low-frequency fixed-path sound in a continental shelf region with internal-wave activity Duda, Timothy F.; Collis, Jon M.; Lin, Ying-Tsong; Newhall, Arthur E.; Lynch, James F.; DeFerrari, Harry A. (Acoustical Society of America, 2012-02)Sound at 85 to 450 Hz propagating in approximately 80-m depth water from fixed sources to a joint horizontal/vertical line array (HLA/VLA) is analyzed. The data are from a continental shelf area east of Delaware Bay (USA) ...