Acoustic nonlinearity of the upper ocean and shallow sea and features of the scattering and absorption of sound

  • V. A. Bulanov V.I. Il'ichev Pacific Oceanological Institute FEB RAS
DOI: 10.29006/1564-2291.JOR-2018.46(2).2
Keywords: acoustic nonlinearity, scattering, absorption of sound, sea water, the upper layer of the ocean, bubbles, shallow sea

Abstract

The marine environment is characterized by existence of various small-scale inhomogeneities, which exist near the sea surface and in the water column: gas bubbles, different suspended matter, plankton of different sizes, microturbulence, etc. All of these reasons inhomogeneities add your contribution to the acoustic characteristics of the marine environment, including nonlinear characteristics which are important for hydroacoustics. Despite the importance of the nonlinearity parameter for the marine environment, information on measurement of it at sea is very scarce. In the paper features of linear and nonlinear acoustic characteristics of sea water containing small-scale heterogeneities are discussed. The results of studies of acoustic nonlinearity of sea water and the absorption of sound at different depths in situ are presented. A comparison are obtained for the local acoustic parameters and for coefficients of backscattering of sound in the upper ocean to a depth of 100 meters. It is shown that the acoustic characteristics change significantly with depth and the observed anomalies in absorption and nonlinearity due to the presence of heterogeneous inclusions. It is shown that peculiarities of the spatial structure of the scattering coefficient of sound due to changes in the structure of the bubble clouds entrained wind stress and induced currents at a wind speed of 12 m/s. It is discussed the relationship of scattering and absorption of sound with the acoustic nonlinearity of sea water. It is shown the ability to predict the distribution of acoustic nonlinearity and sound absorption in the ocean and in the shallow sea on the basis of remote sensing data for backscattering of sound.

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Published
2018-11-18
Issue
Vol 46 No 2 (2018): Journal of Oceanological Research
Section
Ocean acoustics

Transfer of copyrights occurs on the basis of a license agreement between the Author and Shirshov Institute of Oceanology, RAS