## 3 Results and Discussion  
As mentioned above, this paper will analyze the possibility of manipulating the flame to completely extinguish it by exposing the flame source to acoustic waves. For this research, first, a diagram of the sound pressure as a function of frequency was obtained for a fixed distance. The electrical power that is required to be delivered to the extinguisher to extinguish the flames was then determined. The possibility of a change of parameters makes it versatile (it is possible to adjust its parameters to extinguish flames from a specific kind of substance--in this case paraffin wax). As mentioned earlier, even harmonics were applied, referring to their orders that are possible to obtain by means of Fourier series decomposition. Below, for illustrative purposes, tabulated summaries of both the sound pressure level at which this phenomenon was observed (Tables 2 and 4) and the power that had to be delivered to the high-power acoustic extinguisher sound source for complete flame extinguishment are presented (Tables 3 and 5). In practice, the order of the harmonics was changed in the range of two to ten. By extreme harmonics, harmonics of the order of two and ten are meant. Therefore, the results in Tables 2-5 are shown for these higher harmonics analyzed (i.e., even harmonics of the second and tenth orders). This may allow one to notice certain regularities in both the sound pressure level and the power that had to be delivered to the sound source to observe the phenomenon of complete extinguishment of the flames. In turn, to facilitate the interpretation of the results obtained, the summary diagrams formed on the basis of all acquired data (from the samples for the even harmonics analyzed) are presented in Figures 4 and 6. Below in Table 2, the experimental results obtained for the lowest order of higher harmonics, i.e., the second order, are presented. As the frequency increased, a gradual increase in the sound pressure level at which the flames were extinguished was observed. Figure 3: Cascade bars diagram of equivalent acoustic pressure Leq [dB] corresponding to the limit levels [%]. \begin{table}
\begin{tabular}{c c} \hline \hline
**f [Hz]** & **SPL [dB]** \\ \hline
14 & 125.6 \\
15 & 125.7 \\
16 & 126.4 \\
17 & 129.2 \\
18 & 127.4 \\
19 & * \\
20 & * \\ \hline \hline \end{tabular} \({}^{*}\)The 'Protect’ thermal protection in the power amplifier tripped; the power delivered to the speaker was about 1000 W.  
\end{table} 
Table 5: Minimum electrical power values that had to be delivered to the extinguisher to extinguisher the flames, as a function of frequency and higher harmonics (order 10), for a low-frequency sinusoidal waveform. \begin{table}
\begin{tabular}{c c} \hline \hline
**f [Hz]** & **SPL [dB]** \\ \hline
14 & 120.7 \\
15 & 123.6 \\
16 & 123.9 \\
17 & 124.7 \\
18 & 125.7 \\
19 & 126.7 \\
20 & 126.9 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Sound pressure values observed at the point of flame extinguishing, as a function of frequency and higher harmonics (order 2), for a low-frequency sinusoidal waveform with the use of a high-power acoustic extinguisher. \begin{table}
\begin{tabular}{c c} \hline \hline
**f [Hz]** & **SPL [dB]** \\ \hline
14 & 85 \\
15 & 210 \\
16 & 240 \\
17 & 290 \\
18 & 370 \\
19 & 510 \\
20 & 580 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Sound pressure values observed at the point of flame extinguishing, as a function of frequency and higher harmonics (order 10), for a low-frequency sinusoidal waveform with the use of a high-power acoustic extinguisher. \begin{table}
\begin{tabular}{c c} \hline \hline
**f [Hz]** & **SPL [dB]** \\ \hline
14 & 120.7 \\
15 & 123.6 \\
16 & 123.9 \\
17 & 124.7 \\
18 & 125.7 \\
19 & 126.7 \\
20 & 126.9 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Minimum electrical power values that had to be delivered to the extinguisher to extinguisher the flames, as a function of frequency and higher harmonics (order 2), for a low-frequency sinusoidal waveform. extinguished.