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The results of experimental study of the spatial structure of the scalar-vector acoustic field formed during towing of a tone low-frequency emitter over the shelf of the Sea of Japan are discussed. The experiment was accomplished by towing the source of a tone signal with a frequency of 134 Hz at a depth of 20 m over various acoustic tracks at distances up to 10 km from an integrated receiving system consisting of a receiver of acoustic pressure and three orthogonal components of the acoustic pressure gradient. Special attention has been focused on study of the interference structure of the scalar and vector fields with provision of the technical reliability of the method and the results of the experiment under controlled hydrological conditions. We discuss the quantitative characteristics and peculiarities of the interference formation along tracks that differ in depth. The unique results of comparing the horizontal and vertical components of the fields are most interesting of all. They allowed us to reveal the existence of eddy structures in the acoustic field of the source over several tracks. We analyze the possibility of practical application of the results of our research. [ABSTRACT FROM AUTHOR]

The paper discusses the results of an experiment conducted in the Sea of Japan in March 2016 on an acoustic track 194 km long under winter hydrological conditions. We have studied the most complex case of propagation of pulse pseudorandom signals from the shelf into shallow water during vortex generation on the acoustic track. Analysis of the experimentally obtained pulse characteristics have shown that the maximum first approach of acoustic energy recorded at all points agrees well with the calculation. This testifies to the fact that at a given reception depth, the first to arrive are pulses that have passed in the near-surface sound channel over the shortest distance and at small angles close to zero. We propose a technique for calculating the mean sound velocity on the track from satellite monitoring data on the surface temperature, which makes it possible to rely on the successful application of the results obtained in acoustic ranging and navigation problems. [ABSTRACT FROM AUTHOR]

The paper discusses the results of an experiment conducted in the Sea of Japan in March 2016 on an acoustic track 194 km long in winter hydrological conditions. The most complex case of propagation of pseudorandom pulse signals from the shelf to deep water in the presence of gyre formation on the acoustic track. An analysis of the experimentally obtained pulse characteristics show that at all points, a maximum, in terms of amplitude, first arrival of acoustic energy is recorded. This is evidence that at a given depth horizon, pulses that have passed the shortest distance through a near-surface sound channel at small angles close to zero are received first. The calculation method of mean sound velocity on the track, based on the satellite data of surface temperature monitoring, is proposed. We expect that the results obtained with this method can be successfully used for the purposes of acoustic range finding and navigation. [ABSTRACT FROM AUTHOR]

A hardware-software complex that allows synchronous measurements of hydroacoustic noises and signals, the temperature, and the pressure at a specified point and provides transmission of theses characteristics via a radio channel and their recording in a shore-based analytical center is described. The offshore part of the complex includes a GPS receiver for testing the location during drift. The results of an experimental approbation of the complex during acoustic thermometry of a water area in the Vityaz bay of the Posiet gulf in the Sea of Japan are presented. [ABSTRACT FROM AUTHOR]

Solving the problems of underwater acoustic communication and navigation for controlling underwater objects greatly depends on a correct estimation of the hydrological and acoustical environment in the region. Analysis of the domestic and foreign experience in the field of navigational support of self-contained underwater devises shows that, to solve the problem, it is technically and economically advantageous to deploy a set of fixed sources of navigation signals in the region with a range of coverage that is at least not less than the size of the region of interest. At long distances and, especially, in a shallow-water sea, the key factors in solving the problem of navigation are correct determination of the efficient sound speed and the time of signal propagation for each path connecting sources and receivers. [ABSTRACT FROM AUTHOR]

Presents a study that assessed the possibility of using acoustic tomographic techniques for monitoring water mass structure and dynamics of the Sea of Japan. Value of acoustic tomography; Characterization of the Sea of Japan; Location of acoustic sources and receivers.

The article discusses the study on the formation of effective velocity of navigation signal propagation in various directions and its influence on measurement accuracy. It states that the study was conducted in Poset Bay on the Sea of Japan shelf zone and had used time-synchronized broadband transmitters on the bottom close to Capes Suslov, Sylchkov, and Shul'ts. It says that a radiohydroacoustic buoy (RHB) which was equipped with radio transmitter and a cable line with a hydrophone receiver, was utilized. Results of the study show the importance of navigational signal transmitter location to ensure positioning accuracy. It suggests to place transmitters in a way wherein effective sound velocities, which join transmitters and autonomous unmanned submersibles (AUSs), are equivalent.

The article focuses on the research of the effect of tide on sound field formed along a fix track in the shelf zone of the Sea of Japan. The experimental study aimed to prove the possibility of using the calculated tide level in examining the dependence of the pulse travel along various ray paths for reconstructing the temperature field in a shallow water. It was found out that numerical simulation and high-accuracy measurements of signal propagation times in shallow-water were needed.