Abstract
The article discusses the features of interference in sonar channels. Sonar or interference associated with the noise of the marine environment, or noisy media sonar channel communications equipment. Under noisy environments understand the noise of the sea itself (dynamic noise), ice, biological, seismic and technical noise. Noise protection act as a natural field interference, unmanageable and determines the limit of technical feasibility of reducing the intrinsic noise of the sonar channel communications equipment. Noises sonar equipment carrier communication channel due to the radiation of acoustic energy into the water over a wide frequency band due to operation of the propeller of the machines, auxiliary machinery and the hull interaction with the oncoming flow of water. By the nature of the interaction with the interference signal is classified as additive and multiplicative. Contribution of selected sources in the total field of noise depends on several factors, such as the ship's speed, placement and cowling design and so on. A quantitative assessment of the impact of interference to the reception of sonar signals characterized by the use of correlation functions or power spectra (intensity), knowing that estimated noise perceived by receiving acoustic antenna. In terms of receiving signals multiplicative noise equivalent power increase interference. They lead to a decrease in signal / noise ratio at the receiver input. However, their characteristic is that their impact, in contrast to the additive noise, cannot be compensated by increasing transmission power. Therefore, to assess the real noise immunity of signal reception and evaluation of the capacity of hydro-acoustic communication system is necessary to know the laws of the distribution of instantaneous values of the level and phase of the signal at the receiver input. A specific kind of interference is the interference associated with the manifestation of the Doppler effect. The sonar system due Doppler effect caused by relative movement between the emitting and receiving antennas. As a result of research obtained: evaluation of a one-dimensional function of the noise densityW(U), estimate of the expectationand variance of the noise .

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