Denoising ultrasonic pulse-echo signal using two-dimensional analytic wavelet thresholding

作者：Hoseini Mohammad R; Zuo Ming J^*; Wang Xiaodong

来源：Measurement, 2012, 45(3): 255-267.

DOI：10.1016/j.measurement.2011.12.007

• Ultrasonic testing
• B-scan
• Analytic wavelet thresholding
• Stationary wavelet transform

When an ultrasonic angle-beam pulse-echo setup is used, two kinds of noise are present in the received signal: (1) wedge noise, and (2) random noise. In this study, we propose a method for removing both random and wedge noises using a two-dimensional stationary wavelet transform (2D SWT). To improve the performance of the 2D SWT, we employ analytic wavelet thresholding. This requires calculating the analytic signal for a 2D signal and extracting the envelope of the signal, but no regular generalization of analytic signals to multi dimensions is available. We prove that under some certain conditions, the envelope of the ultrasonic B-scan can be extracted exactly by introducing a reference vector. The performance of the proposed denoising method is assessed using simulated and experimental data. The experimental results show that our proposed denoising method is able to reveal the echoes from a surface breaking crack as small as 0.1 mm.

• 出版日期2012-4