## 5 Conclusions  
1. Studies of the relationship of AE parameters with the features of various technological processes have shown that these parameters can be used in the conditions of automated production as a supplement to the existing monitoring tools or separately.
2. As a result of studies of some technological processes, including blade processing and processing with concentrated energy flows, features of changes in the spectral composition of acoustic signals, a characteristic of many technological processes using different principles of energy impact on the material being processed, were established.
3. It was found that the main reason for the impact on changes in the characteristics of the acoustic signal is the change in the power density of the energy impact on the workpiece material. The power density, defined as the impact power per unit of surface, changes with a change in the power of the energy source, with an increase in the impact surface area, and with the extension of the time of the duration of the energy pulses accompanying the treatment. A decrease in power density entails a drop in the amplitude of the high-frequency component of acoustic signals compared to the low-frequency component.
4. For practical use of acoustic signal parameters, the ratio of RMS amplitudes of acoustic signals in the low and high frequency ranges can be controlled. An increase in this ratio indicates that the pulses of energy action on the material have become smaller in amplitude or have become more stretched over time. That is, changes in the  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Mounting Conditions** & **Low Frequencies, kHz** & **High Frequencies, kHz** & **K\({}_{\text{f}}\)** \\ \hline \multirow{2}{*}{Normal mounting} & 0.4–3 & 5–8 & 0.8 \\ \cline{2-4}  & 0.4–3 & 10–20 & 3 \\ \hline \multirow{2}{*}{Loose mounting} & 0.4–3 & 5–8 & 9 \\ \cline{2-4}  & 0.4–3 & 10–20 & 35 \\ \hline \hline \end{tabular}
\end{table}
Table 2: K\({}_{\text{f}}\) values depend on tool mounting conditions.  
Figure 22: Comparison of AE spectra in the range of low (**a**) and high (**b**) frequencies when boring with the same modes: 1—normal tool mounting; 2—loose mounting.  
technological process led to a drop in the power density of the impact on the material. In laser processing, this is associated with a shift in the focal plane. In WEDM, it is associated with an increase in the concentration of erosion products. In blade processing, it is associated with an increase in tool wear, an increase in the area of impact of the cutting edge and, accordingly, the transition to a viscous mechanism of crack formation when the chip elements are shifted.  
Conceptualization, S.N.G.; methodology, M.P.K.; software, A.N.P. and Y.A.M.; validation, Y.A.M.; formal analysis, V.D.G. and Y.A.M.; investigation, M.P.K. and A.N.P.; resources, A.N.P.; data curation, M.P.K. and V.D.G.; writing--original draft preparation, S.N.G.; writing--review and editing, M.P.K.; visualization, A.N.P. and Y.A.M.; supervision, S.N.G. and M.P.K.; project administration, M.P.K.; funding acquisition, S.N.G. All authors have read and agreed to the published version of the manuscript.  
This work was supported financially by the Ministry of Science and Higher Education of the Russian Federation (project No. FSFS-2021-0003).  
Not applicable.  
The data presented in this study are available on request from the corresponding author.  
The study was carried out on the equipment at the Center of Collective Use of MSUT \"STANKIN\", supported by the Ministry of Higher Education of the Russian Federation (project No. 075-15-2021-695 from 26 July 2021, unique identifier RF 2296.61321X0013).  
The authors declare no conflicts of interest.