## 1 Introduction
Compared with the trend prediction of the rockburst based on the physical and mechanical properties of rock [22; 23], the short-term warning technology was the foreword research and hotspot discussion of rockburst disaster prevention and control, such as Acoustic Emission (AE), Microseismic (MS), and Electromagnetic Radiation (EMR) [24; 25; 26]. The accumulation of cracking can be observed and the occurrence trend of rockburst disasters can be assessed by acoustic emission monitoring technology [27; 28; 29]. The AE is a kind of phenomenon where the local damage inside material is caused by an external load and the accumulated energy in the form of elastic waves is swiftly released [30; 31]. In the 1930s, [PERSON] and [PERSON] first discovered that rock-like materials produced acoustic emission phenomena under external loads [32; 33]. Since then, researchers have launched a large amount of research and discussion on the correspondence between the rock mechanical properties and acoustic emission characteristic parameters. In engineering applications, acoustic emission monitoring will generate a huge amount of data, and the processing of acoustic emission monitoring data is the current main research direction. The acoustic emission parameter method was one of the fundamental analysis methods which was widely promoted in engineering practice. For example, [PERSON] et al. [34] predicted the concrete beam's ultimate bending capacity by the energy value of the acoustic emission signal, which was further extended to bridge tests. [PERSON] et al. [35] established the early warning system based on AE cumulative counts and AE energy value variation characteristics of gas-bearing coal-rock at different deformation and failure stages. The acoustic emission event was used for tomographic calculation, [PERSON] et al. [36] studied rockburst in coal test specimens under over-stress conditions and true-triaxial unloading. [PERSON] et al. [37] investigated the relationship between the mechanisms causing damage and acoustic emission ring counts of coal samples for different freezing conditions. Acoustic emission parameter data were calculated based on the part of signals that exceeds the threshold value. Compared to the acoustic emission parameter analysis, acoustic emission waveform analysis by preserving the complete original signal was able to reflect more truly the evolution process of failure in a comprehensive and detailed way. Therefore, there are a growing number of scholars who have begun to use acoustic emission waveform analysis to study the cracking and failure of rock materials. [PERSON] and [PERSON] [38] found that the ratio of tensile and shear crack was related to dominant frequency characteristics of acoustic emission waveform. [PERSON] et al. [39] used the high-frequency band of the AE signal to monitor the granite failure process under uniaxial compression. Through AE signal frequency-amplitude distribution, [PERSON] et al. [40] proposed an assessment method of rock-salt destruction under the test condition of multilevel cyclic loading. [PERSON] et al. [41] identified fracture mechanisms of cementitious composites by using the wavelet transform of AE signals. The peak frequency of acoustic emission signals after wavelet transform as a parameter exhibited good stress memory capabilities for the Kaiser effect [42]. To simulate the stress conditions of a rockburst, the indoor true-triaxial test system was adopted by loading on five surfaces in three directions, except for a single free surface. Meanwhile, the entire test process can be monitored by acoustic emission monitoring technology, as well as the high-speed camera being able to record the occurrence phenomenon of experimental rockburst. The mechanism of rockburst was researched more accurately by waveform analysis, which conducted the wavelet decomposition and reconstruction to the effective acoustic emission signal. In consideration of the lack of literature on the topic, our findings provide a detailed evaluation of the current problem.