Parameter Optimization And Errors Analysis On Near-field Acoustic Holography

Along with the promotion of the application of near field acoustical holography technology, the contradiction between the technology's powerful ability of sound field recons-tructtion and high demand of thick data measurement points is more and more obvious. In order to enhance the engineering application ability of this technology, how to reduce the spatial sampling points and the area of the hologram on the condition that the reconstruction result is correct and the reconstruction precision is high needs to be researched.In this article, the elementary theory of near field acoustical holography based on the spatial transformation of sound field(STSF) algorithm has been infered. And next, parameter selection scope of this algorithm has been researched. In order to reduce the spatial sampling points, this article establishes the hologram data interpolation theory based on Helmholtz equation least squares method(HELS) method. The simulation example indicated that if use this method to carry on the hologram data interpolation, three or four sampling points of each wave length are enough and on the hologram, survey points may be reduced about 70%-80%. In order to reduce the area of the hologram, this article uses data zero padding and the wave number domain filter method to reconstruct sound field on the condition that the hologram aperture is small. If the hologram aperture is too small, in order to overcome the windowing effects and wraparound errors, statistically optimal near-field acoustical holography (SONAH) is introduced. It can reconstruct the sound field accurately and can be the supplementation of STSF.Finally, to confirm the solution proposed by this article, a near field acoustical holography experiments are carried out. The experimental results indicated that the STSF algorithm is correct and the parameter selection scope proposed by the article is reasonable. The algorithm based on combine of HELS data interpolation method and the SONAH can reconstruct sound field accurately in the condition of small hologram aperture and few sampling points of each wavelength.