一种基于WMM的超声信号噪声抑制新方法

A novel WMM method based de-noising for ultrasonic signal

超声衍射时差(time of flight diffraction,TOFD)法存在接收的缺陷衍射信号能量低、易于被噪声干扰的问题.为了解决这一问题,根据TOFD法检测过程中两相邻测点回波中缺陷信号具强相关性、噪声信号具随机性的特点,在传统小波模极大值(waveletmodular maximum,WMM)方法的基础上,提出一种改进的噪声抑制技术.分别利用传统和改进的WMM方法对计算机仿真信号及焊缝实测信号进行处理.结果表明,和传统的WMM方法相比较,改进方法对噪声的抑制更为有效,对不同性质的噪声具有更好的适应性,能够在很大程度上提高缺陷信号的辨识能力.

Ultrasonic TOFD (time of flight diffraction) has the shortcoming of sensitive to noise for the lower amplitude in the tested signal.According to the characteristics that the defect waves have strong correlation and the noise non-correlation in TOFD tested two adjacent A-scan lines,an improved WMM (wavelet modular maximum) method based de-nosing is proposed.Computer simulated and weld tested signals are de-nosing processed by using conventional and improved WMM methods correspondingly.The experimental results show that the improved method is more effective in noise suppression and has better adaptability for different noise.Compared with the conventional method,the proposed technique can greatly improve the ability of identifying defect wave.