De-noising using wavelet packet for ultrasonic testing signal of small diameter steel pipe with thick wall

摘要

In the ultrasonic detection of small-diameter steel pipe with thick wall, the quality of ultrasonic echo signals is the foundation for the pipeline flaw identification and feature extraction. In this paper, a de-noising method of wavelet packet based on threshold is proposed for the limitation of soft and hard thresholds. The ultrasonic wave pipeline detection signal contaminated by noise is de-noised by this method. Moreover, the contrastive analysis is performed among the wavelet packet transform based on adjusted threshold, original ultrasonic echo signal and the wavelet packet transform based on default threshold. Experiment results show that the noise reduction effect of the wavelet packet based on the adjusted threshold is obvious and the SNR of signals is also improved.