Reseach On Measuring And Analysing Of Low Noise Target’s Radiated Noise

The radiater noise measuring is a efficient approach to evaluate the quiet level of underwater targets in the wate and develop the research on reducing the radiater noise.However,with the development of related technology,the radiated noise of some underwater targets is getting lower and lower,so it is more difficult to measure the radiater noise exactly now.For the request of measuring lower noise of quiet underwater targets,this thesis make the method of measuring and analysing of near field target’s noise as the research subject,focus on the way of measuring lower noise of underwater targets and the method of signal processing,then get a measuring system to validate the measuring and processing method above.This thesis introduce the background of measuring low noise of underwater targets firstly,then summarize the history and current situation of measuring radiated noise,and explain the measuring conditions of near field and far field in noise measuring.Getting several methods of measuring low noise of underwater targets though the theory of measuring radiatd noise and passive sonar equation.This subject gets a set of low noise measuring system base on vertical line array,getting a longer distance and a better result of measuring through improving SNR according to the directivity of the array,building a buoy dipping type measuring system base on the precise positioning of the buoy,lower TL from shortening the measur distance,and achieve the purpose of measuring the noise of quiet underwater targets.Studing on the method of signal processing,focus on the beamforming method of vertical line array in near field,getting the direction and distance of the targets to the measuring array according synchronization measuring,forming the beam that points to the direction of the target with beamforming technology.Reduce the side-petal according to the beam-control technology,optimize the direction characteristic of the measuring array.After simulating the theory with computer,compiling a kind of software to process the signal of vertical line array and the noise parameters.For validating the measuring method and signal processing method in this thesis,unfold static state and dynamic experimentations on the lake.Mearsuring the signal of the analog sound source and small ship with uniform motion in a straight line,the result turns out that the noise measuring system and the method of signal processing are in a position to get a good effect of measuring,and can be used in measuring underwater targets’ radiater noise in near field,and then carry this thesis’ s point.