Noise elimination method of ultrasonic echo signal based on empirical and variational hybrid decomposition

Ultrasonic defect detections are easily disturbed by complex noise in ultrasonic echo signals. To improve the accuracy of ultrasonic defect detection, an ultrasonic echo signal noise elimination method based on the hybrid decomposition is proposed. The fusion of empirical mode decomposition and correlation coefficient is used to preprocess the ultrasonic echo signal, and the preprocessing signal is obtained to eliminate the low-frequency noise components. Based on variational mode decomposition, the preprocessed signal is decomposed into several band-limited intrinsic mode functions (BLIMFs), and the mutual information is introduced to estimate the optimal mode number. The useful modes are extracted according to the correlation coefficient of the BLIMFs to the preprocessed signal, and the denoising results are reconstructed. The denoising performance of the proposed method is evaluated by simulation and measured ultrasonic echo signals. Compared with two existing methods, experimental results show that the proposed method can simultaneously eliminate high-frequency and low-frequency noises in ultrasonic echo signals. Under different SNR conditions, the mean SNR of the EMD, VMD and the proposed method are 10. 01 dB, 9. 48 dB, and 16. 09 dB, respectively, which proves the superiority of the proposed method for noise elimination of the ultrasonic echo signals. © 2023 Science Press. All rights reserved.