材料或结构受外力或内力作用下产生的声发射信号，其频率成分复杂，包括一些能量相对微弱的高频信号和低频干扰信号,而研究中往往只针对某些频率段信号进行分析。小波包变化可以将复杂频率成分的信号分解到不同的频率段，通过频率和能量筛选，可以将感兴趣的相对高能量的频率段信号提取分离出来。以Q235试件拉伸试验中采集到的声发射为例进行小波分析，证实了小波分析方法在声发射信号降噪中的实用价值。

Acoustic emission, which was produced when the material or structure received the external force or internal force, had a complex components, including some high-frequency signal with low relative energy and some disturbance signal with low frequency. In research, only some frequency bands are thought to be interest, and needed to be analyzed. The signals with complex frequency components can be decomposed into different frequency bands by wavelet packet transformation. Then, the signals required will be extracted by frequecy and energy factor. The acoustic emission signals produced during the tensile test of steel Q235 was acquired and proceeded by wavelet transform and energy analysis. Testing results showed the capability of the denoise value of wavelet method on acoustic emission signals.