Since the flexural waves in the plate would produce scattered waves when they propagated through the flaw of a plate , the measured signals of a strain gauge contented the direct waves propagated from the impact source and the scattered waves propagated from the flaw 藉由小波转换进行讯号的时频分析,进而求得弯曲波由冲击点至各应变规的波程时间,并计算出弯曲波在各频率中的波群速度。