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A wavenumber-fitting extrapolation method for FFT-based near-field acoustic holography using microphone array

Near-field acoustic holography (NAH) is an important acoustic visualization technique which can be implemented efficiently through the fast Fourier transform (FFT). However, when the FFT is applied on a small measurement aperture via a microphone array, significant spectral leakage occurs. Windowing is often employed to reduce this leakage but at the expense of degradation in reconstruction performance due to the corruption of measured data, especially when the source is located around the edge of the sensor array. A wavenumber-fitting method is proposed to extrapolate the measurement aperture effectively. This is achieved by exploiting the wave equation using measurement aperture as the boundary condition. The quality of NAH source reconstruction is shown to be improved significantly using the proposed approach.