Research On Application Of Patch Nearfield Acoustic Holography Using Sound Field Separation With Double Planes

Nearfield acoustic holography (NAH) is an effective tool for identifying and reconstructing noise and visualizing sound field. After years of development, appeared patch near-field acoustical holography -- Patch NAH, which only on local measurements to reconstruct the sound source. This approach reduces the workload of NAH, expanded the scope of application of NAH technology. However, Patch NAH technologies are still in need a free sound field environment, so they are difficult to solve the problem of identification and reconstruction of sectional noise.Therefore, this dissertation proposed double planes Patch NAH technology, which applies the Sound field separation technology to the Patch NAH.Its theoretical basis and the Implementation are researched and the computer simulations and experiment demonstrate its feasibility and effectiveness. So the problem of identification and reconstruction of sectional noise will be solved, the scope of application of NAH will be extended further. The main contents in the dissertation is summarized as follows:In chapter one, the history of Patch NAH and the Sound field separation technology has been reviewed, and the current status and problems existed in NAH have also been analyzed.Then the main research content has been determined in the dissertation.In chapter two, theoretical basis of the double planes Patch NAH technology are introduced. The Theoretical system contains: the theory of NAH based on the spatial transform of sound field; nearfield acoustic holography based on k-space data extrapolation method; Sound field separation technique.In chapter three, implementation steps of double planes Patch NAH technology are studyed, and source of error and the controls are researched. The computer simulations demonstrate its feasibility and effectiveness.In chapter four, according to the previous idea, experiment study is used to examine this method's effectiveness and accurateness.In the speaker source experiment, many frequency are tested, by the analysis of experiment, the double planes Patch NAH technology has been verified.In chapter five, researches in this dissertation have been summarized, and the topics need further study have been proposed.