Multi-stage adaptive noise cancellation for ultrasonic NDE

Adaptive noise cancellation techniques are ideally suited for reducing spat ially varying noise due to the grain structure of material in ultrasonic no ndestructive evaluation. Since grain noise is generally uncorrelated, in co ntrast to the correlated flaw echoes, adaptive filtering algorithms exploit the correlation properties of signals in a C-scan image to enhance the sig nal-to-noise ratio of the output signal. In this paper, a multi-stage adapt ive noise cancellation method is proposed for enhancing flaw detection in u ltrasonic signals. The overall method is based on the use of an adaptive le ast mean square error filter with primary and reference signals derived fro m two adjacent positions of the transducers. Results of implementing the pr oposed algorithm on ultrasonic signals obtained from hard-a inclusions in t itanium will be presented. (C) 2001 Elsevier Science Ltd. All rights reserv ed.