A new type of wavelet - exponential damping wavelet is constructed to detect the knocking sound caused by mechanical faults in an engine , experimental results show that by this wavelet effective features of those faults can be extracted from noise signal 为了识别发动机噪声信号中表徵故障的间歇性撞击声,本文构造的一种新型的小波指数衰减型小波函数,它能有效地识别出间歇性撞击声。