Internal wave effects on acoustic propagation
Duda, Timothy F.
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Internal gravity wave induced acoustic fluctuations are reviewed. It is well known that internal waves cause temporal and spatial variability above and beyond that caused by mesoscale and larger ocean heterogeneity. Increasingly detailed work over many decades has shown that deep-ocean internal waves, which have often been parameterized using the Garrett-Munk spectrum as a guide, are responsible for rapid acoustic field variability at all propagation ranges. Numerous experiments have shown that various sections of wavefronts from impulsive sources have fluctuation qualities well-described by theory, simulation, or both. In contrast, fluctuations in shallow water experiments, although known to be consistent with those expected from internal waves via theoretical and simulation arguments, are incompletely described by theories for a number of reasons. These reasons include nonstationary, inhomogeneous or anisotropic wave environments, unknown geoacoustic properties, and rapidly changing background currents, all of which prevent detailed comparison of observation and prediction. At this time, many different shallow-water internal wave scenarios give rise to similar field fluctuations, within reasonable confidence intervals for the predictions. This may simplify order-of magnitude fluctuation prediction, while simultaneously making inversion and highly-detailed prediction problematic.
Underwater Acoustics Measurements (UAM) 1st International Conference “Underwater Acoustic Measurements: Technologies & Results,” 28 June- 1 July 2005, Heraklion, Crete, Greece,
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Observationally constrained modeling of sound in curved ocean internal waves: Examination of deep ducting and surface ducting at short range Duda, Timothy F.; Lin, Ying-Tsong; Reeder, D. Benjamin (Acoustical Society of America, 2011-09)A study of 400 Hz sound focusing and ducting effects in a packet of curved nonlinear internal waves in shallow water is presented. Sound propagation roughly along the crests of the waves is simulated with a three-dimensional ...
Observed limiting cases of horizontal field coherence and array performance in a time-varying internal wavefield Collis, Jon M.; Duda, Timothy F.; Lynch, James F.; DeFerrari, Harry A. (Acoustical Society of America, 2008-08-28)Using a moored source and horizontal/vertical line array combination, horizontal coherence properties of high signal to noise ratio (>=20 dB) 100–1600 Hz signals have been measured. Internal waves in the area of the ...
Experimental evidence of three-dimensional acoustic propagation caused by nonlinear internal waves Frank, Scott D.; Badiey, Mohsen; Lynch, James F.; Siegmann, William L. (Acoustical Society of America, 2005-08)The 1995 SWARM experiment collected high quality environmental and acoustic data. One goal was to investigate nonlinear internal wave effects on acoustic signals. This study continues an investigation of broadband airgun ...