Statistical problem of a low-frequency sound propagation in shallow-sea waveguide with two-dimensional random inhomogeneities is considered. Transmission loss law for average intensity in the case of fluctuating thermocline and absorbing liquid bottom is investigated. Within the framework of local-mode approach it is shown that mode coupling with the distance is of local character if there are no strong fluctuations of modal wavenumbers in stochastic waveguide. So, in the local-mode approach the mode coupling to be the certain supplement to adiabatic approximation of intensity, and it does not change seriously the average transmission loss. Comparison between results of local-mode and diffusion approximation is also carried out.
43.30.Ft Volume scattering
43.30.Re Signal coherence or fluctuation due to sound propagation/scattering in the ocean
$^1$V.I. Il'ichev Pacific Oceanological Institute, Far-East Branch of Russian Academy of Sciences
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