## 5 Conclusions  
In AET, an elastic wave-based method, deterioration of the elastic wave until it reaches a sensor, particularly in highly heterogeneous materials such as concrete, is the subject of many studies. This study investigated the correction of AE signals recorded in fiber-reinforced concrete by 3D-PCT. First, attenuation properties of concrete samples including different types and amounts of fibers were revealed. Effects and differences of the concrete content on the damage types and attenuation properties showed that the presence of the fiber increases the concrete heterogeneity and causes more attenuation of the AE signals. The type and amount of fiber is effective in attenuation: steel fibers cause more elastic wave attenuation than synthetic fibers. Then, the samples were tested under flexure, and AE results were compared with mechanical findings after parameter correction. AE hits having different amplitudes recorded by the same sensor can be perceived as having equal amplitude due to different attenuation factors. The presence of the steel fiber decreases the level of closeness between recorded and corrected amplitudes, while synthetic fibers increase it. In addition, as concrete is more attenuative than cement mortar, amplitude values recorded in cement mortar are also closer to the recorded ones. The closeness of recorded amplitude to the corrected amplitude of AE signals in fiber-reinforced concrete was defined with the equation of \(y=x^{1.03}\).  
The effectiveness of the proposed correction method was verified by clustering fiber activities from concrete cracking activities for the first time in the literature with WPF and PP. Cluster-1 (50-200 kHz) was associated with cement paste damage for both concrete, fiber-reinforced concrete, and cement mortar specimens. Cluster-2 (200-250 kHz) was only seen in fiber-inclusive specimens. Fiber activities are distinguished more clearly after parameter correction by recalculating amplitude and RA values. Successfully matched fiber activities were revealed after correction and their origination times obtained from frequency-based unsupervised pattern recognition show that more accurate AE interpretation could be made with parameter correction technique for excessive heterogeneous concrete structures. In addition, an inference was proposed for a relationship between the amplitude and energy losses of the AE signals and the type of damage after parameter correction.  
Conceptualization, methodology, S.T. and N.A.; writing S.T.; review and editing, N.A. All authors have read and agreed to the published version of the manuscript.  
This research was funded by TUBITAK (The Scientific and Technological Research Council of Turkey, grant number 118M172.  
Not applicable.  
Financial support provided by TUBITAK to conduct this research under grant number 118M172 is greatly acknowledged. The authors are also thankful to Atlas 1 for supplying BetonFiber HE 0735 type hooked steel fibers and to KORDSA for supplying KraTos Micro Synthetic Fiber and KraTos Macro Synthetic Fibers.  
Figure 15: An inference based on the 3D-PCT results is the relationship between amplitude and energy losses with the damage type.