Patch near-field acoustic holography based on the modified Helmholtz equation least squares method

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Journal of Vibration and Shock ›› 2014, Vol. 33 ›› Issue (10) : 157-161.

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Patch near-field acoustic holography based on the modified Helmholtz equation least squares method

WANG Ran，CHEN Jin，DONG Guang-ming

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Abstract

Fast Fourier transform (FFT)-based near-field acoustic holography (NAH) requires that the measurement aperture should completely enclose the source, which is impractical for large-scale sound sources. Helmholtz equation least squares (HELS) method allows for patch reconstruction. However, it’s not suitable for reconstructing acoustic radiation from coherent multiple sources or a complicated source which consists of several separated parts. To circumvent this difficulty and enhance the reconstruction accuracy, a new patch NAH technique based on the modified HELS method is proposed. The modified HELS method expresses the acoustic field of a complicated source as the superposition of the coherent acoustic radiation from all of its separated parts. Using the acoustic pressures reconstructed with the modified HELS method, the measurement surface is extended through an iterative procedure. In the end, taking the extrapolated pressures as input data, the acoustic field can be reconstructed more precisely. Numerical simulation and experimental results demonstrate that this method can reconstruct the acoustic field of a complicated source and enhance the reconstruction accuracy.

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modified HELS / data extrapolation / patch NAH / acoustic field reconstruction

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WANG Ran;CHEN Jin;DONG Guang-ming. Patch near-field acoustic holography based on the modified Helmholtz equation least squares method[J]. Journal of Vibration and Shock, 2014, 33(10): 157-161