## 1 Introduction
studied the influence of acoustic waves on flames using a laminar diffusion line [43]. Changing environmental parameters affects the direction of propagation of the flame front and consequently the thermal emission until the flammability limit is exceeded [25; 44]. [PERSON] et al. showed that it is easier to extinguish flames using low-frequency waves [45]. This is also confirmed by other research results e.g., [46; 47; 48]. The fuel load slightly affects the extinguishing pressure, and the flame-extinguishing process depends on the cumulative effect of the average acoustic flow and oscillation disturbances [45; 49]. Increasing the distance between the waveguide output and the flame source results in the need to deliver more power to the sound source. The possible relationship between the average flow effect and excitation frequency was also investigated (in practice, changes were noted with the increase in pressure level) [27]. [PERSON] et al. determined the relationship between the acoustic wave parameters and the sound pressure and intensity of the acoustic wave [50]. This research enabled the representation of the geometry of the acoustic wave beam outside the waveguide. The acoustic pressure was noted to decrease with increasing distance from the waveguide output. Depending on the frequency of the wave, it was observed that there was a seventeen-fold difference in the power that had to be delivered to the sound source (woofer) to be able to extinguish the flames, with a three-and-a-half-fold difference in pressure. [PERSON] et al. determined the pressure threshold below which flame extinction was not observed [51]. The experimental results obtained from the extinguishing tests confirmed visualizations of the complete flame extinction obtained using a tracer apparatus. These authors noted the need to use high and very high acoustic powers to improve the effectiveness of extinguishing flames with acoustic waves. The use of low power to extinguish flames is associated with the limited range of the acoustic method (basically, no one has investigated so far the possibility of extinguishing flames using acoustic waves at a distance of more than a few cm). To increase the range between the extinguisher tip and the source of the flames, it is necessary to conduct experiments on a much larger scale (and this can be achieved with the use of large and very large powers delivered to the sound source). Furthermore, the extinguishing abilities of acoustic waves of different frequencies and modulations are not thoroughly analyzed (state-of-the-art), especially with the use of high and very high powers. Therefore, it was necessary to partially fill the gap in this area. As shown in the works of [PERSON] et al., large and very large acoustic powers have been used in Central and Eastern Europe in an effort to develop an acoustic extinguisher that generates a directional acoustic field [19; 28; 31; 46; 48; 52] and can have an intelligent module [38; 39; 40; 41; 42]. This made it possible to increase the distance between the waveguide output (i.e., the extinguisher output) and the fire source, and to build an autonomous device that does not require manual switching when flames are detected. In the case of using very-low-frequency waves, an increase in the amplitude of the vibrations is observed, which is a certain technical limitation (frequency mismatch is associated with vibrations of the sound source diaphragm) [28; 31; 46]. As part of the project being developed with Bulgarian scientists, so far, work has been carried out on the possibility of applying an acoustic fire extinguisher equipped with an artificial intelligence module to detect (using deep neural networks) and extinguish flames with acoustic waves without using typical fire protection measures. It may in the long run make this technology a cutting-edge approach in fire safety solutions. This is possible through the continuous development of artificial intelligence [53; 54; 55; 56]. [PERSON] et al.