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Theoretical Studies On Vector Acoustic Field And Vector Signal Processing

Posted on:2005-02-23Degree:DoctorType:Dissertation
Country:ChinaCandidate:D J WangFull Text:PDF
GTID:1102360155468754Subject:Underwater Acoustics
Abstract/Summary:PDF Full Text Request
Sound propagation and signal processing model are the two fundamental theories of underwater acoustic systems, which are the same to that based on vector hydrophone. When vector sensor processing techniques have shown many advantages than pressure after more than ten years of rapid development, it is necessary to do more fundermental researches on physics and signal theory to explore the potential of vector hydrophone more specifically and effectively. We attempt to make probe fundermentally in above two espects in the thesis.Near distance acoustic fields are payed attention in intelligent acoustic mine and the measurement of tranquil targets' radiate field and acoustic feature monitor of targets in the haven, etc. So in the thesis methods of acoustic field prognosis of near distance are discussed.Lateral wave contributes greatly to near distance acoustic field, which is only estimated approximatively in open literature and these have great errors. In this thesis accurate numerical prognosis method for lateral wave field is given, so the near distance acoustic field may be predicted accurately.Only based on accurate prediction of near distance pressure field the particle volicty field can be caculated by numerical differential method. This is satisfied by the near distance acoustic field method studied in this thesis.Since vector hydrophone is being widely applied step by step, it is necessary to comprehend near distance vector field. By numerical analysis physical concepts about the particle velocity field are descripted in the thesis.Results of acoustic field prognosis on wave theory, normal model and ray model are compared, and the approximate degree of the later two models is given. Normal mode is fit to forecast far distance acoustic fields only, but not near distance. Ray model is fit to forecast high frequence acoustic fields. If kh>100, ray model is accurate adequately.In the other part of the thesis the fundamental theories of vector signal processing are studied. Methods based on acoustic energy flow solve someinherent shortcomings of traditional pressure signal processing methods and increase processing gain and DOA estimation accuracy. Methods based on acoustic energy flow have been verified to be practically useful by trials. And to model those methods is necessary and practically significant.The frequency measurement model and its parameters are deduced in the thesis. Based on this model it's convenient to express the probability densities of cross spectrum and average acoustic intensity and DOA, and to make deep analysis of vector signal processing methods' performance sequentially.Based on the frequency measurement model, probability densities of acoustic energy flows such as cross spectrum and average acoustic intensity are deduced, then ROC (receiver operating characteristic) and vector array's gain are theoretically analysed. In isotropic noise field, acoustic energy flows' ROC is 4dB higher than pressure's. Vector array's gain is higher than that of pressure array. Under the condition of high snr, the vector array's gain based on high orders surpasses that based on acoustic energy flows.Based on frequency measurement model probability densities and Crame-Rao Low Boundary (CRLB) of DOA estimation are deduced. At low snr DOA estimation is bias. If snr is higher than 7dB/Hz, the estimation is an unbiased MLE (Maximum Likelihood Estimation) and its accuracy approaches CRLB.The studies of near distance acoustic field and signal processing theories coincide with simulations and sea (lake) trials rationally.Exordium of the thesis introduces fundamental knowledge about theories and techniques of vector hydrophone, and overviews the corresponding development status at home and abroad, so that readers can have a general acquaintance with them.
Keywords/Search Tags:Vector hydrophone, Vector acoustic field, Vector signal processing, Pekeris waveguide, Lateral wave, Frequency model of vector hydrophone, Acoustic energy flow, Probability density, Underwater acoustic engineering
PDF Full Text Request
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