Generation of the Noise Bursts Associated with Nonlinear Internal Waves in Shallow Water

Boris Katsnelson, Professor of University of Haifa, Dept of Marine Geosciences, Haifa, Israel, Oleg A Godin, Naval Postgraduate School, Department of Physics, Monterey, CA, United States and Qianchu Zhang, University of Haifa, Marine Geosciences, Haifa, Israel
Abstract:
The present paper extends the earlier analysis of the wideband noise burst generated in the presence of nonlinear internal waves with respect to quantification of physical mechanisms initiating noise on the base of a more diverse set of NIW events by exploiting the acoustic data obtained at sites with a wider range of water depths and over a longer observation period. Recent paper of authors [J. Acoust. Soc. Am. (2019), Vol. 145, No. 3, Pt. 2, p.1670] reported observations during Shallow Water 2006 experiment of repeated increase in acoustic noise intensity fluctuations by up to 35-40 dB in the frequency band from 10 to 5000 Hz on multiple near-bottom hydrophones. Three distinct physical mechanisms are analyzed, which are probably responsible for increased noise in different frequency bands. They are: turbulence of the water flow past hydrophones, sediment transport, and sediment saltation. Correlation between the velocity of the internal tide-induced near-bottom currents and noise intensity at low and mid-frequencies is investigated. [Work supported by ONR, NSF, and BSF.]
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