Use of Linear Receiving Arrays for Observing Horizontal Refraction of Low-Frequency Sound in Shallow Water with a Strongly Inhomogeneous Waterlike Bottom

Numerical simulation is applied to study the features of a low-frequency (55 and 137 Hz) acoustic field and its recording by linear horizontal and vertical arrays in a shallow-water waveguide with a depth of ≈30 m and an inhomogeneous bottom. The area where the sound speed in the bottom is close that in water is considered. For calculations, we used the spatial distribution of the sound speed in the Kara Sea bottom sediments, obtained during engineering seismic survey, as well as test drilling data. It is shown that an inhomogeneous bottom not only affects the depth-averaged loss during sound propagation, which can be detected by a vertical array, but also leads to horizontal refraction of acoustic waves, which manifests itself during beamforming at an extended horizontal array. The maximum effects are observed for a low frequency (55 Hz): the decrease in transmission losses reaches 5 dB, and the bias in the maximum response of the array is 3.4°.