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Type: Journal article
Title: Green's function approximation from cross-correlations of 20-100 Hz noise during a tropical storm
Author: Brooks, L.
Gerstoft, P.
Citation: Journal of the Acoustical Society of America, 2009; 125(2):723-734
Publisher: Acoustical Soc Amer Amer Inst Physics
Issue Date: 2009
ISSN: 0001-4966
Statement of
Laura A. Brooks and Peter Gerstoft
Abstract: Approximation of Green's functions through cross-correlation of acoustic signals in the ocean, a method referred to as ocean acoustic interferometry, is potentially useful for estimating parameters in the ocean environment. Travel times of the main propagation paths between hydrophone pairs were estimated from interferometry of ocean noise data that were collected on three L-shaped arrays off the New Jersey coast while Tropical Storm Ernesto passed nearby. Examination of the individual noise spectra and their mutual coherence reveals that the coherently propagating noise is dominated by signals of less than 100 Hz. Several time and frequency noise normalization techniques were applied to the low frequency data in order to determine the effectiveness of each technique for ocean acoustic applications. Travel times corresponding to the envelope peaks of the noise cross-correlation time derivatives of data were extracted from all three arrays, and are shown to be in agreement with the expected direct, surface-reflected, and surface-bottom-reflected interarray hydrophone travel times. The extracted Green's function depends on the propagating noise. The Green's function paths that propagate horizontally are extracted from long distance shipping noise, and during the storm the more vertical paths are extracted from breaking waves.
Keywords: acoustic correlation
acoustic noise
acoustic wave interferometry
Green's function methods
ocean waves
oceanographic techniques
underwater acoustic propagation
DOI: 10.1121/1.3056563
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Appears in Collections:Aurora harvest
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