An improved joint method for onset picking of acoustic emission signals with noise

Abstract

The onset times of acoustic signals with spikes, heavy bodies and unclear takeoffs are difficult to be picked accurately by the automatic method at present. To deal with this problem, an improved joint method based on the discrete wavelet transform (DWT), modified energy ratio (MER) and Akaike information criterion (AIC) pickers, has been proposed in this study. First, the DWT is used to decompose the signal into various components. Then, the joint application of MER and AIC pickers is carried out to pick the initial onset times of all selected components, where the minimum AIC position ahead of MER onset time is regarded as the initial onset time. Last, the average for initial onset times of all selected components is calculated as the final onset time of this signal. This improved joint method is tested and validated by the acoustic signals with different signal to noise ratios (SNRs) and waveforms. The results show that the improved joint method is not affected by the variations of SNR, and the onset times picked by this method are always accurate in different SNRs. Moreover, the onset times of all acoustic signals with spikes, heavy bodies and unclear takeoffs can be accurately picked by the improved joint method. Compared to some other methods including MER, AIC, DWT-MER and DWT-AIC, the improved joint method has better SNR stabilities and waveform adaptabilities.

摘要

自动方法难以精确地拾取带有突刺,重体和起跳不清晰声源信号的到时。为了解决该问题,基 于离散小波变换(DWT)、修改能量比(MER)和赤池信息量准则(AIC),提出一种改进的联合拾取方法。 首先,应用DWT 将信号分解成各个分量;其次,联合应用MER 和AIC 拾取所有被选择分量的初步 到时,其中初步到时是MER 到时之前的最小AIC 位置;最后,计算所有初步到时的平均值并作为信 号最终到时。通过不同信噪比和波形的声源信号测试验证改进的联合拾取方法,结果显示信噪比的变 化不能影响改进的联合拾取方法的精度,此外,改进的联合方法能够精确地拾取带有突刺、重体和起 跳不清晰声信号的到时。相比较其他四种方法,该方法有更强的信噪比稳定性和波形适应能力。