Arrival-Time Detection With Multiscale Wavelet Analysis and Source Location of Acoustic Emission in Rock

In order to overcome the difficulties of traditional arrival-time picking techniques applied to acoustic emission (AE) events with low signal-to-noise ratio (SNR) and complex waveforms, this work proposed a new time picking method. It combines the advantage of the wavelet transform technique, the ratio of short-term average to long-term average (STA/LTA) method, and the Akaike information criterion (AIC), which is called the wavelet-STA/LTA-AIC (WSA) picker. This work assessed the performance of picking arrival times of the WSA picker by locating the AE events from pencil-lead breaking on the marble panel (artificial sources) and tensile cracking sources on the granite. For all experiment results, the proposed WSA picker shows less location error compared with the AIC picker, regardless of geometry and source type. For location results of the pencil-lead breaking events on the marble panel, the average location errors are 1.4 cm (AIC picker) and 0.6 cm (WSA picker). For location results of the tensile cracking events on granite, the WSA picker is more concentrated in the region of the fracture surface and has fewer wrong-locating points at the specimen edge when compared with the AIC picker. It demonstrates that the proposed WSA picker can improve the accuracy and capability of AE location and can be a viable method for arrival-time picking.