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Underwater navigation system based on Doppler shift – measurements and error estimations

Ostrowski Zawisza, Salamon Roman, Kochańska Iwona, Marszal Jacek

Polish Maritime Research

2020

nr 1

180--187

A new acoustic navigation system was developed to determine the position and speed of moving underwater objects such as divers and underwater vehicles. The path of an object and its speed were determined by the Doppler shifts of acoustic signals emitted by a transmitter placed on the object and received by four hydrophones installed at the periphery of the monitored body of water. The position and speed measurements were affected by errors mainly caused by acoustic reflections (returns) from the water body boundaries and surface reverberations. This paper discusses the source of the disturbances with the results of a simulation test and experimental measurements. It was demonstrated that the magnitude of the errors could be acceptable in most of the potential applications of the acoustic navigation system.

Underwater Noises of Open-Circuit Scuba Diver

Korenbaum Vladimir, Kostiv Anatoly, Gorovoy Sergey, Dorozhko Veniamin, Shiryaev Anton

Archives of Acoustics

2020

Vol. 45, No. 2

349--357

The features of respiratory noises and noises of fins for open-circuit scuba divers, indicating a multipole character of noises emission, are specified in cameral conditions. It demonstrates a possibility to detect low-frequency components of noises of fins with pressure gradient sensor in near field. A possibility of estimating the respiratory rate of an open-circuit scuba diver is demonstrated at distances up to 100 m in real sea. It gives an opportunity of estimating the bearing (time delay in a pair of hydrophones) for the open-circuit scuba diver by respiratory noises at distances up to 150 m in real sea. Thus, low-frequency underwater noises of open-circuit scuba divers may be successfully applied to monitor the safety of diving and to prevent waterside intrusion by trespassers.

Signal conditioning for examination of shallow-water acoustic noise correlation properties

Rudnicki M., Marszal J.

Hydroacoustics

2016

Vol. 19

335--340

The article describes the process of signal conditioning for examination of acoustic noise correlation properties in shallow water. Knowledge of these properties is very important for the design processes of passive and active hydroacoustic systems. This paper focuses on the above issue from the point of view of passive sonar. In sonar systems, signal processing algorithms operate on both useful acoustic signals, and accompanying noise. Quantitative estimation of the correlation properties of acoustic noise enables an accurate determination of detection conditions. This will verify the validity of certain commonly used simplified models in simulations of hydroacoustic systems. The article presents how the measurement system was constructed, and the structure of files for storing measurement data. It describes the processing algorithm developed for the measured signal conditioning. Research results are presented and discussed.