Regularization method for the application of K-space data extrapolation to near-field acoustical holography

A regularization method for applying the K-space data extrapolation method to near-field acoustical holography (NAH) is proposed. The influence of the finiteness of measurement aperture is a serious impediment to the NAH reconstruction of structural vibration when the size of the measurement aperture is smaller than that of the structure. The K-space data extrapolation method has been proposed to reduce the influence of this finiteness. An appropriate regularization method is necessary to apply the K-space data extrapolation method if the measured pressure is contaminated by noise. Some regularization methods for NAH have been proposed. However, it is difficult to determine an appropriate K-space filter if the finiteness of the measurement aperture becomes an issue. An estimation method of appropriate regularization filter for applying the K-space data extrapolation method is proposed to solve this difficulty. The effectiveness of this method is demonstrated by simulations. The simulation results confirm that (1) an appropriate regularization filter may be constructed to realize spatial wave number characteristics similar to that of ideal full aperture and (2) the reconstruction error is sufficiently suppressed by the proposed method. (C) 2004 Acoustical Society of America.