The Study On Quick Source Diagnosis And Identification Of The Radiated Noise Of The Underwater Structure

The radiation noise always has been one of the main performances which measure thecombat effectiveness and survivability of the ship, which is the main detection objective of avariety of passive sonar and acoustic weapons, the most important factor in destructing itssound stealth performance, directly affect the performance of the ship’s sonar station, thusreducing this type radiation noise of underwater vehicle is significant. In order to carry out thenoise control and provide the actual basis for the noise indicators of the underwater vehicle’sacoustic design, carry out the research of the technology of noise sources identificationlocation. Estimate the size of these noises contribution of the every noise source in theunderwater vehicle and the space distribution of the noise sources, then for the largercontribution of the noise source take the noise reduction measures, and provide the a solidtechnical support for developing the underwater vehicles which has a high hiddenperformance. Therefore the study of this quick diagnosis and recognition technology of suchunderwater structures has a significant meaning for reducing the vibration and the noise andimproving their stealth ability. But there has some difficulties in researching such underwaterstructures, which included how to efficiently obtain measurement data, and study thecorresponding data processing algorithms; how to complete measurements by using fewerhydrophones to reduce measurement costs; how to obtain more meaningful engineeringapplications and other issues by utilizing the sound pressure and the vibration velocity of thesound field. Do the following research for these questions in the underwater structures’ noisesource location identification.At first, briefly describes the research background in the underwater structures’ noisesource location identification, overview its basic characteristics, reviewed and summarizedthe development of the noise source identification and near-field acoustic holographytechnology, and particularly focused on the near-field acoustic holography technology. Forthe underwater large structures’ noise source location identification by using NAH, discussedin detail advantages and disadvantages of the existing noise source identification methods,proposed the need to solve the problem in this situation, and established the basis for thisstudy.Then studied the basic theory of the Helmholtz equation least squares (HELS),obtained the approximation solution of the vibrating body acoustic field, on this basis, derivedHELS method based on velocity measurements, and combining HELS algorithms based on velocity measurements and HELS basic algorithm for data processing, for the existenceproblem of dispersion non-posed, proposed utilizing regularization method to reduce theeffect of errors. By numerical simulation, obtained this algorithm can accurately identify thesource under a certain conditions, while the sound pressure-velocity joint processingalgorithms can separate coherent sound sources, in order to obtain a certain reconstructionaccuracy of the sound field, required the ratio of the measure surface and the reconstructionsurface at least1.2, and here required at least three sampling points between the two sourceswhen there are multiple sound sources; In the measurement signal including the noise, it musttake the regularization method to derive the correct solution, after comparison found that ithas obvious effect when decreased SNR; It can accurately separate each amount of soundfield of a single sound source by using sound pressure-velocity joint approach from thecoherent sound field, especially for the larger contribution of the source to the sound fieldwhich has a more reconstruction precision. Due to the basic algorithm based on soundpressure measurements reconstruct the vibration velocity has a lower accuracy, it is moreappropriate to analyze the sound pressure in the sound field separation and extended theapplication scale of HELS algorithm.Research the selection of the parameters for holographic measurement andreconstruction process in HELS algorithm, including the adaptation points’ position, thenumber of basis functions, the sampling interval, the location and size of the measuringsurface, studied the existence of optimal parameters by numerical simulation, combined withphysical mechanisms of HELS algorithms and mathematical models, analyzed the rationalityof each optimal parameters, quickly obtained optimal parameters, so as to provide the basisfor the HELS algorithm applying the engineering quickly and efficiently with the smallermeasurement surface.Research the movement acoustic holography method based on mobile frameworktechnology,processed the measurement data which exists Doppler frequency shift, obtainedthe spatial distribution of the sound field with no relative movement, combining with HELSproposed noise source identification methods of movement structures for handling thearbitrary shape; For coordinates errors in underwater measurement, utilized MUSIC near-fieldfocused beamforming correcting the sound source trajectory, through a series of numericalsimulations obtaining the following conclusions: the algorithm is only applicable in the caseof Mach less than0.1; When existing multiple sources in complex sound field, the combinedonly applies to the radiation field with the sound source’s frequency less than2.5kHz; It canget the similar accuracy with twice size of the sound surface by only1.3times the sound source surface by this algorithm, which can provide the convenience for its engineeringapplications; After utilizing the modified data reconstructing the sound field, the amplitudereconstructive accuracy and phase reconstructive accuracy have all exist differentimprovements, which proved the correctness and effectiveness of the algorithm,andefficiently resolved the problem for the long measurement time.Study the theory and application based on HELS algorithm of patch near-field acousticholography. Firstly proved the completeness of the approximation sound field and utilizing aseries of spherical wave functions of the weighted from a mathematical view, provides a solidtheoretical basis for applying HELS algorithm extrapolation in the sound field; Secondly theextrapolation process and the steps for reconstructing the sound field is given in detail; Finally,researched the selection of the parameters and the accuracy of reconstructed field in thiscombination algorithm, analyzed the size of the measurement surface and the selection of theextrapolation area by simulation, and compared with the conventional sound fieldreconstruction methods. By analyzing obtained that it existed a minimum measurementsurface can ensure a certain degree of sound field reconstruction accuracy and saving theproject cost; Extrapolation of data points does not exceed the actual measured data points. In asmall measuring aperture, Patch NAH based on HELS algorithm e has far superiorreconstruction performance to the conventional NAH, which has a slightly higher engineeringvalue.Finally carry out the test research of underwater near-field location and identificationmethod for noise sources, investigate the feasibility and accuracy of noise sources locationand identification based on this paper’s methods. Introduced hardware platform of the mufflerpool, designed to complete a full set of hydrophone arrays and acquisition systems,experimental methods and the implementation process. Based on above, as a research objectwith a spherical source in the muffler pool, completed a experimental study for the noisesource location and identification, and the laboratory experimental data acquisition; In theSonghua Lake test to process a test study by a cylindrical and fish lips transducer, completedthe acquisition of the outside experiment data; Finally, experimental results show that: thismethod is feasible and accurate, and provided a basis for its application in engineering.