Energy Classification of Acoustic Events Using the Coda of a Signal

A new energy classification method is proposed for acoustic events recorded in laboratory experiments on rock destruction. The method analyzes the coda waves of acoustic emission (AE) events. Coda waves are considered as reverberation of the acoustic field in the test sample. The new classification was tested on two experiments carried out on different rocks: granites of the Voronezh massif and Berea sandstone, on an INOVA-1000 controlled hydraulic press at the Borok Geophysical Observatory (GO), Schmidt Institute of Physics of the Earth, Russian Academy of Sciences (IPE RAS). Comparison of the new classification with the one used at Borok GO showed that both methods give well consistent results in the middle range of energies of AE events. For strong events with the saturated initial parts of the signals due to the limitations of the recording equipment, the new technique demonstrated better results, leading to energy estimates of such events from the undistorted coda of the signal.