Application On Wave Superposition Approach Of Multiple Ball Field In Sound Pressure Reconstruction Of Patch Near-field Acoustic Holography

Patch near-field acoustical holography（PNAH）technology have more and morewidely application in engineering because of its unique advantages. Wave SuperpositionApproach（WSA）is a equivalent source method in fact. WSA was applied to PNAHtechnology, its computational efficiency and precision are very high because of simplealgorithm and without tedious iterative process. At the same time, the researchers like itmore and more due to there is no border in the singular integral problem. But when PNAHtechnology based on WSA to reconstruct acoustic field it found that virtual source surfaceand source surface of the sound source, measuring surface and source surface’s conformalproblem have heavy influence on the precision of the reconstruction. The number ofvirtual source also is such.In this case, with the support of natural science fund project in Guangxi of study onacoustical holography fast algorithm based on WSA of multiple ball filed, the article putsforward a kind of PNAH of data reconstruction algorithm based on WSA of multiple ballfield. The method reduce reconstruction problem of poor accuracy caused of the virtualdomain and measuring the non conformal problem by using multiple virtual sphere sourceintensity configuration domain,and introduce multiple ball field of two-dimensional fastFourier transform (2D-FFT) algorithm quickly and accurately holographic sound pressure.First, two dimensional fast Fourier transform (2D-FFT) expression of external fieldradiation pressure on multiple virtual ball field is derived by expanding the unknownsource and the integral kernel function of virtual source surface distribution with Fourierseries of exponential form on circumferential and meridian direction. Then, virtual sourceexpansion coefficients can be obtained by using the small hologram aperture pressure data,Then， using the sound pressure expression to achieve near-field sound pressureextrapolation of the holographic data. Finally, using NAH algorithm to space transformreconstruction of ideal sound field acoustic quantity to complete sound fieldreconstruction. In the process of reconstruction, it will reasonable use of regularizationmethod to suppress the reconstruction error. And by the pulsating ball simulation examplesverify the effectiveness and feasibility of this method. The content of each chapter brieflysummarized as follows:The chapter one, the research background and the trend of NAH technology andexisting PNAH three mainstream algorithm, review the advantages with disadvantages toillustrate its existing problems, in order to solve the problem reasonable derivation thispaper’s point of view.The chapter two, introduce the discrete simple virtual source of basic theory of wavesuperposition method of near-field acoustical holography and two-dimensional fastFourier transform algorithm, the discomfort of holographic reconstruction qualitative andregularization techniques.The chapter three, By adopting continuous distribution in multiple virtual sphere source on the surface of the strong function of Fourier expansion, was established basedon FFT algorithm multiple virtual ball field wave superposition method of near-fieldacoustical holography extrapolation formula, based on virtual ball multiple field ofnear-field acoustical holography acoustic field reconstruction algorithm, through thenumerical example verifies the effectiveness and feasibility of this method.The chapter four, analyzed the distance between the sound source surface andholographic measurement surface and hologram surface size on the effect ofreconstruction error, through the numerical example analysis, some principles obtained byreduce some of these factors affect the reconstruction accuracy.The chapter five, the researches in this paper are summarized, put forward furtherstudy of some topics to solve the problem.