改进的小波阈值消噪法应用于超声信号处理

Application of improved threshold denoising based on wavelet transform to ultrasonic signal processing

超声检测中回波信号信噪比低、易于被噪声淹没,小波变换是一种有效的提取缺陷回波的方法.建立了超声缺陷回波信号的数学模型,对基于小波变换的软、硬阈值消噪法作了改进,提出一种折中方法用于超声缺陷回波信号的去噪,同时以信噪比为目标函数对参数的选取也作了优化.仿真实验结果表明,改进方法非常适合用于超声信号的分析,能够很好地抑制噪声,它最大程度的发挥了小波软、硬阈值消噪法的优点,避免它们的缺点,使用该方法处理的信号相对于小波软、硬阈值消噪法在一定程度上改善了去噪的效果,提高了回波信号的信噪比.

The signal to noise ratio of ultrasonic echoes signal was low, the echoes signal was submerged easily in ultrasonic testing, and wavelet transforms was an effective method by which the flaw echoes can be extracted. The mathematics model of ultrasonic echoes signal was established, including the flaw echoes and the noise, the traditional soft and hard threshold denoising methods based on wavelet transform was ameliorated, and a middle course method was put forward for signal denoising in ultrasonic testing. At the same time the parameters selection was also optimized with the signal to noise ratio of ultrasonic flaw echoes signal as object function. The simulation experimental results showed that this method was fit for analyzing ultrasonic signal, and it can depress noises well. This method utilized the advantage of the soft and hard threshold denoising methods and avoided their disadvantage in the farthest. Compare to the traditional soft and hard threshold denoising methods, the denoising effect was improved in a certain extent, and the signal to noise ratio of ultrasonic flaw echoes signal was improved by using this method.