Acoustic emission noise reduction: A case of a uniaxial compression test of gypsum-like rock

In acoustic emission tests, the effective signal generated by crack initiation and propagation inside a sample is easily affected by the testing machine, earth vibration and other external noise, which increases the difficulty of data processing and analysis. To solve this problem, a gypsum sample under uniaxial compression is taken as an example to analyze and process the acoustic emission signal during the experiment. The test results show that these noises generally have the characteristics of acoustic sources far from the probe and signal types different from the effective signal. Therefore, a series of methods concerning the noise reduction of acoustic emission signals, including acoustic emission signal preprocessing, acoustic source distance denoising, and acoustic source type denoising, is proposed. Through three analyses and treatments of acoustic emission parameters, noise reduction was achieved with good results. According to the principles of these methods, some suggestions have been put forward for the position of probes in acoustic emission tests; that is, the connection of two probes should not be perpendicular to a weak plane (bedding, joints, etc.). These results could provide a theoretical reference for the postprocessing of acoustic emission signals in mechanical tests.