No abstract

Flaw signals measured in ultrasonic testing include the effects of the measurements system and are corrupted by noise. The measurement system response is both bandlimited and frequency dependent within the bandwidth, resulting in measured signals which are blurred and distorted estimates of actual flaw signatures. The Wiener filter can be used to estimate the flaw's scattering amplitude by removing the effect of the measurement system in the presence of noise. A method is presented for implementing an optimal form of the Wiener filter that requires only estimates of the noise distribution parameters. The theoretical error for scattering amplitude estimation, assuming various levels of available prior information, is analyzed. Three estimation techniques, one a maximum-likelihood based method and the other two residual-sum-of-squares methods, are formulated and tested. The results demonstrate that any of the three approaches could be used to optimally implement the alternative form of the Wiener filter with limited prior information.

The Wiener filter is currently used in the ultrasonic scatterin~ amplitude estimation problem as a means of desensitization during deconvolution [1,2,3]. The work summarized here focuses on a Wiener filtering approach which incorporates ~ priori flaw and noise information. It will be shown that this approach leads to improved scattering amplitude estimates and improved radius estimates. BACKGROUND

No abstract