## 5 Experimental Results and Discussion
### Results
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & \multicolumn{3}{c}{**MP 1**} & \multicolumn{3}{c}{**MP 2**} & \multicolumn{3}{c}{**MP 3**} \\ \cline{2-7}  & **50 Hz (dB)** & **100 Hz (dB)** & **50 Hz (dB)** & **77 Hz (dB)** & **50 Hz (dB)** & **108 Hz (dB)** \\ \hline Long—CP1 & 10 & 32 & 7 & 28 & 19.5 & 32.5 \\ Long—CP2 & 18 & 17 & 18.5 & 29.5 & 18 & 25.5 \\ Lat—CP1 & 18 & 29 & 6 & 9 & 8.5 & 27.5 \\ Lat—CP2 & 17 & 24 & 15.5 & 18.5 & 6.5 & 21.5 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Optimal noise attenuation results of the two secondary setups for all CP, MP, and frequencies. MP 3 (6.5 dB), while it is sufficient in MP 2 (15.5 dB). The same setup offers a reduction of 18.5 dB at 77 Hz in MP 2. Although this is satisfying, it is far less than the maximum attained attenuation with the longitudinal source at the same position (29.5 dB). For the higher frequencies of 100 Hz and 108 Hz faced in MP 1 and MP 3, the longitudinal source at CP 1 attains the highest attenuation of 32 and 32.5 dB, respectively. In Figure 10, the genetic evolution with random mutation for the primary field attenuation at each MP and frequency is depicted for the two optimal cases, as presented in Table 2.  
As far as investigations in the GA operation are concerned, the evolution is also tested using adaptive mutation (\(\left[p_{low},p_{high}\right]:\left[0.3,0.1\right]\)). The genetic evolution for each case is depicted in Figure 11, along with the corresponding one from Figure 10 for comparison purposes. It is shown that the optimal results given in Table 2 not only can be reached but this is also achieved in earlier generations. This is expected, as the adaptive mutation replaces strings of low fitness with higher probability and drives to selective pressure; thus,  
Figure 10: Evolution of noise attenuation for the two best cases of each MP and frequency. fitter solutions tend to appear in earlier generations. The optimal results of the genetic evolution with the adaptive mutation are given in Table 4. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**MP**} & **Frequency** & **CP** & **Control** & **Max. Noise** & **Optimal Driving** \\  & **(Hz)** & & **Setup** & **Reduction (dB)** & **Parameters** \\  & & & & **\{\{a_1 (dB), \(a_{2}\)(dB), \(\Delta\)\(\varphi\)(deg)\}\}** \\ \hline \multirow{2}{*}{\(1\)} & 50 & 2 & Long & 18 & 5, 1.5, 135 \\  & 100 & 1 & Long & 32 & 3.5, 3, 90 \\ \hline \multirow{2}{*}{\(2\)} & 50 & 2 & Long & 18.5 & 4, 7.5, 270 \\  & 77 & 2 & Long & 29.5 & 1.5, 4.5, 180 \\ \hline \multirow{2}{*}{\(3\)} & 50 & 1 & Long & 20 & 5.5, 1.5, 225 \\  & 108 & 1 & Long & 32.5 & 2, 5.5, 45 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Optimal noise attenuation results with adaptive mutation for the best case of each MP and frequency. Figure 11: Evolution of noise attenuation for the best case of each MP and frequency, with random (red) and adaptive (green) mutation. The \(\Delta\varphi\) is an important degree of freedom. Various steps of \(45^{\circ}\) seem to offer a significant contribution in searching for successful noise attenuation. The third gene has a crucial role in the fitness score, as solution sets with the same \(\Delta\varphi\) and close first and second genes can obtain the same score, i.e., \(\{3.5,3,90\}=\{3.5,2.5,90\}=32\), while individuals with the same first two genes and different \(\Delta\varphi\) may have far different scores, i.e., \(\{3.5,3,90\}\
eq\{3.5,3,315\}=-3.5\), resulting in noise reinforcement. Therefore, while some of the optimal driving parameters in Table 4 slightly differ in some \(a_{1}\) and \(a_{2}\), they produce the same fitness with the corresponding results in Table 2. In any case, the optimal \(\Delta\varphi\) value remains the same, with either random or adaptive mutation.