title: Temporal coherence of acoustic signals in a fluctuating ocean.
abstract: Temporal coherence of acoustic signals propagating in a fluctuating ocean is important for many practical applications and has been studied intensively experimentally. However, only a few theoretical formulations of temporal coherence exist. In the present paper, a three-dimensional (3D) modal theory of sound propagation in a fluctuating ocean is used to derive closed-form equations for the spatial-temporal coherence function of a broadband signal. The theory is applied to the analysis of the temporal coherence of a monochromatic signal propagating in an ocean perturbed by linear internal waves obeying the Garrett-Munk (G-M) spectral model. In particular, the temporal coherence function is calculated for propagation ranges up to 10(4) km and for five sound frequencies: 12, 25, 50, 75, and 100 Hz. Then, the dependence of the coherence time (i.e., the value of the time lag at which the temporal coherence decreases by a factor of e) on range and frequency is studied. The results obtained are compared with experimental data and predictions of the path-integral theory.
authors.affiliation: The National Oceanic and Atmospheric Administration/Earth System Research Laboratory, 325 Broadway, Boulder, Colorado 80303, USA.
authors.forename: Alexander G
authors.initials: AG
authors.lastname: Voronovich
authors.forename: Vladimir E
authors.initials: VE
authors.lastname: Ostashev
authors.forename: John A
authors.initials: JA
authors.lastname: Colosi
mesh_terms: D000162:Acoustics; D003198:Computer Simulation; D016014:Linear Models; D008962:Models, Theoretical; D009038:Motion; D009716:Numerical Analysis, Computer-Assisted; D009792:Oceans and Seas; D012815:Signal Processing, Computer-Assisted; D013016:Sound; D013997:Time Factors; D014867:Water
chemical_list: D014867:Water