基于改进Hilbert-Huang变换的超声回波信号去噪研究

超声回波信号中包含大量有关缺陷性质的信息,由于信号在检测和传输过程中不可避免地受到随机噪声干扰,给后续信号处理带来误差。针对该问题,提出改进的希尔伯特-黄变换(Hilbert-Huang Transform,HHT)应用于超声回波信号去噪,提取回波信号中反映缺陷本质特征的信号。改进算法引入小波包变换对超声回波信号作预处理,对处理后的信号进行经验模态分解,提出对数似然检验法,识别并去除噪声引起的虚假分量,重构出有用回波信号。通过对添加高斯白噪声的超声回波信号去噪,验证改进算法应用于超声回波信号去噪的可行性和有效性。

Studies of Ultrasonic Echo Signal De-noising Based on Improved Hilbert-Huang Transform

The ultrasonic echo signal contains a large number of information reflects defect properties. Echo signal also has various noise in defecting and transmission that brings error. Proposed improved Hilbert-Huang transform (HHT) and applied it to the ultrasonic echo signal de-noising, extraction of echo signal reflects the essential characteristics of the defect. Improved algorithm put forward wavelet packet which doing pretreatment for signal firstly. Proposed the log-likelihood test which was with the log-likelihood value of each intrinsic mode function component and the original signal as the judgment basis to identify and remove illusive components. Then useful defect echo signal was reconstructed. Finally, by de-noising the ultrasonic echo signal with Gaussian white noise, the results demonstrate feasibility and effectiveness of the improved HHT.