Propagation Features of Pseudorandom Pulse Signals from an Extended Shelf into the Deep Sea upon Reception at Different Depths

The results of an experiment conducted in the Sea of Japan in August 2023 on an acoustic path with a length of 144.4 km under summer–fall hydrological conditions are discussed. The case of the propagation of pseudorandom pulse signals from an extended shelf into the deep sea upon reception at depths of 69, 126, 680, and 914 m is examined. The analysis of the experimentally obtained pulse characteristics has shown that a group of ray arrivals with a duration of approximately 0.5 s, with the maximum in the center, is recorded at all depths. The experiment on reception of broadband pulse signals with a central frequency of 400 Hz has been conducted at a distance of 144.4 km from the source of navigation signals (SNSs) located on the shelf at a depth of 30 m and a sea depth of 45 m. Signal information has been received using a system equipped with hydrophones distributed up to a depth of 1000 m, enabling long-term signal recording at fixed depths or during submersion. The experimental findings have made it possible to study pulse characteristics of the acoustic waveguide, to calculate the effective propagation velocities of signals received at different depths, and to conclude about the potential of using measuring autonomous underwater vehicles (AUVs) at depths up to 1000 m to solve the problems of climate monitoring of marine areas.