Horizontal Refraction of Acoustic Waves in Shallow-Water Waveguides Due to an Inhomogeneous Bottom Structure

Abstract

Three-Dimensional (3-D) sound propagation in a shallow-water waveguide with a constant depth and inhomogeneous bottom is studied through numerical simulations. As a model of inhomogeneity, a transitional region between an acoustically soft and hard bottom is considered. Depth-averaged transmission loss simulations using the “horizontal rays and vertical modes” approach and mode parabolic equations demonstrate the horizontal refraction of sound in this region, even if the water column is considered homogeneous. The observed wave effect is prominent at low frequencies, at which the water depth does not exceed a few acoustic wavelengths. The obtained results within the simplified model are verified by the simulations for a real seabed structure in the Kara Sea.

Modeling Techniques for Underwater Acoustic Scattering and Propagation (Including 3D Effects)

“…Papers of the first kind [2][3][4][5][6][7] are related to new or insufficiently investigated physical effects related to sound propagation in complex media with various inhomogeneities, including undulating bottom [3], variations in acoustical properties of the bottom across the propagation path [2], the presence of seamounts [4], and bubbles [6] or internal waves [7] in the water column. It is remarkable that both new 2D [3,7] and 3D [2,4] effects are reported in these papers. In most of them, new interesting features of sound fields are investigated both theoretically and experimentally, and the modeling results are compared with the measurement data.…”

“…In most of them, new interesting features of sound fields are investigated both theoretically and experimentally, and the modeling results are compared with the measurement data. The spectrum of theoretical approaches used by the authors covers almost all techniques existing in theoretical underwater acoustics, including parabolic equations theory [3], normal modes [2], and ray-theoretical considerations.…”