## 3 Results
Thus, in this paper, we compared the empirical distribution functions of the (\(N_{p}/\tau_{p}\)) parameter. The construction of distribution functions was performed using a rolling-window with a size of \(W=75\) signals at a scanning step of 15 pulses. As an example, Figure 8a,c shows the empirical distribution functions of the parameter \(N_{p}/\tau_{p}\), registered when the crack grew to a value of \(l=1.7\) mm. For a numerical evaluation of the scale factor effect, the change in the level quantile \(p=0.8\) ((\(N_{p}/\tau_{p}\))\({}_{p=0.8}\)) was estimated. For specimens with a thickness of \(t=1\) mm, the parameter under study was (\(N_{p}/\tau_{p}\))\({}_{p=0.8}=0.152\) [\(1/\mu\)s]. When processing the AE signals recorded during specimen loading with a thickness of \(t=6\) mm, a decrease in the quantile of the empirical distribution function to the value (\(N_{p}/\tau_{p}\))\({}_{p=0.8}=0.125\) [\(1/\mu\)s] was noted. The decrease in the (\(N_{p}/\tau_{p}\))\({}_{p=0.8}\) parameter for a specimens with a thickness of \(t=6\) mm, was associated with an increase in the proportion of low-energy signals. Figure 7: Time dependences of the “_b-value_” parameter with the superimposed stress curve, for specimens with a thickness of 1 mm (**a**) and 6 mm (**b**). When crack size was about \(l=9.5\) mm (Figure 8b,d), the \((N_{p}/\tau_{p})_{p}=0.8\) parameter also grew to the mean values of \((N_{p}/\tau_{p})_{p}=0.8=0.206\) [\(1/\upmu\)s] for a 1 mm thick specimen and \((N_{p}/\tau_{p})_{p}=0.8=0.181\) [\(1/\upmu\)s] for 6 mm thick specimen. The difference between the maximum and minimum values of the \((N_{p}/\tau_{p})_{p}=0.8\) parameter were \(\Delta(N_{p}/\tau_{p})=0.054\) [\(1/\upmu\)s] for 1-mm specimen and \(\Delta(N_{p}/\tau_{p})=0.056\) [\(1/\upmu\)s] for 6-mm specimen. The relative change in the difference between the mean count frequency of AE signal for specimens with 1 mm and 6 mm thickness is 3.6%. Figure 9 shows the result of plotting the dependence of the maximum values \((N_{p}/\tau_{p})_{p}=0.8\) on the specimens thickness. Figure 8: Comparison of the empirical distribution functions of the mean count frequency \((N_{p}/\tau_{p})_{p}=0.8\) recorded during loading of steel specimens with a thickness of \(t=1\) mm (**a**,**b**) and \(t=6\) mm (**c**,**d**) in the moments when crack length reaches \(l=1.7\) mm (**a**,**c**) and \(l=9.5\) mm (**b**,**d**). Figure 9: The influence of the specimen thickness \(t\) on the \(p=0.8\) level quantile values of the empirical count frequency distribution function \(N_{p}/\tau_{p}\) of AE signals. As noted earlier, a large proportion of high-frequency signals was recorded for small thickness specimens. This fact was confirmed by the maximum value of the specific count frequency of AE signals \((N_{p}/\tau_{p})_{p\,=\,0.8}=0.206\) [1/\(\upmu\)s]. When processing the AE data obtained during specimen loading of greater thickness, a decrease in the \((N_{p}/\tau_{p})_{p\,=\,0.8}\) parameter was registered. For example, an increase in the proportion of low-frequency harmonics in the spectrum of registered AE signals was noted for the 6 mm thickness specimens during experiments. While, the maximum value of the \((N_{p}/\tau_{p})_{p\,=\,0.8}\) parameter corresponded to \((N_{p}/\tau_{p})_{p\,=\,0.8}=0.181\) [1/\(\upmu\)s]. The least squares method was used to synthesize an approximating function that describes the correlation between the \((N_{p}/\tau_{p})_{p\,=\,0.8}\) parameter and the thickness of the object under study. As a result of applying this algorithm for the 30 KhGSA steel, the correlation dependence \((N_{p}/\tau_{p})_{p\,=\,0.8}(t)=0.04\cdot t^{(-0.45)}+0.16\) was obtained, the accuracy of which is confirmed by the coefficient of determination \(R^{2}=0.98\). The scale factor has a considerable effect on the energy characteristics of the registered AE signals.