Truncated aperture extrapolation for Fourier-based near-field acoustic holography by means of border-padding

摘要

Although near-field acoustic holography (NAH) is recognized as a powerful and extremely fastacoustic imaging method based on the inverse solution of the wave-equation, its practicalimplementation has suffered from problems with the use of the discrete Fourier transformation(DFT) in combination with small aperture sizes and windowing. In this paper, a method is presentedthat extrapolates the finite spatial aperture before the DFT is applied, which is based on the impulseresponse information of the known aperture data. The developed method called linear predictiveborder-padding is an aperture extrapolation technique that greatly reduces leakage and spatialtruncation errors in planar NAH (PNAH). Numerical simulations and actual measurements on ahard-disk drive and a cooling fan illustrate the low error, high speed, and utilization ofborder-padding. Border-padding is an aperture extrapolation technique that makes PNAH a practicaland accurate inverse near-field acoustic imaging method.