We investigated the specific features low-frequency (50–300 Hz) sound propagation in shallow-water areas to relatively small distances r ≈ 3H–50H from the sound source, where H is the waveguide depth. The bottoms of water areas were assumed to be fluid homogeneous gas-containing media. Situations were compared in which the sound velocity in the bottom is higher and lower than in the water layer (hard and soft bottom). It was confirmed in experiment that the average effective sound velocity in the bottom may have rather low values (≈100 m/s). The mode description of the acoustic field was used in calculations, and both propagating and outgoing modes, including quasi-modes, were taken into account. The averaged dependences of the field intensity decay on distance were obtained for different frequencies and sound velocities in the bottom. The sound damping factors β in the waveguide were found as functions of frequency and sound velocity in the bottom. It is shown that for a soft bottom, the value of β monotonically increases with an increase in the sound velocity in the bottom, while for a hard bottom, β monotonically decreases. The maximum of β depends on the sound frequency and is reached at the approximate equality of the sound velocities in the bottom and water.

We present the methods and results of numerical experiments studying the low-frequency sound propagation in one of the areas of the Arctic shelf with a randomly inhomogeneous gas-saturated bottom....

Considerable shifts Δ f/ϕ ≈ 10−1of the low-frequency sound field interference pattern in the frequency domain, associated with barotropic tide and internal tidal waves, were observed in the Shallow...

The space-time spectral characteristics of the field of background internal waves (IW) are obtained for two oceanic shelf regions (the Atlantic shelf of the United States and the Kamchatka shelf) and analyzed. Within the framework of a numerical experiment, it is shown that the observed anisotropy of the IW field may considerably affect the low-frequency sound fluctuations in the aforementioned regions and, in particular, may change the interference invariant of the sound field.