## 4 Simulation Experiment
### Experiment Results  
Figure 8 shows a comparison of the acoustic contrast about four methods relative to the change with frequency. From Figure 8, we can see that the acoustic contrast of the ACC method ranges from 8.1056 to 31.1125 dB, and on the whole, different methods produce sound contrast in the order of high and low: ACC method, our method, EDPM method in the bright zone, and PM method in the bright zone. Because the goal of the ACC method is to obtain the maximum acoustic contrast, neither the EDPM method in the bright zone nor the PM method in the bright zone focuses on acoustic contrast; the proposed method controls the sound energy in the dark zone, which will improve the acoustic contrast, so the proposed method produces higher acoustic contrast than the EDPM method in the bright zone and the PM method in the bright zone. In addition to improving the acoustic contrast, the proposed method also needs to consider other factors, which affects the effect of the proposed method on acoustic contrast improvement, so the proposed method produces lower acoustic contrast than the ACC method. The average acoustic contrasts generated by four methods with respect to frequency are shown in Table 2. The average acoustic contrast results generated by four methods are in keeping with Figure 8. The ACC method achieves an average acoustic contrast of 18.3381 dB, the largest of all methods. The average acoustic contrast produced by our method is 2.2898 dB larger than that produced by the PM method in the bright zone and 0.8362 dB larger than that produced by the EDPM method in the bright zone. Figure 9 shows a comparison of the reconstruction error of four methods with respect to the change in frequency. The reconstruction errors of the ACC method are greater than 0 dB, which are the largest among all methods. The reconstruction errors of our method are smaller than those produced by the ACC method, and their values range from \(-12.2945\) dB to \(-1.3299\) dB, but are larger than those produced by the EDPM method in the bright zone and the PM method in the bright zone. The PM method in the bright zone has the smallest reconstruction error, and its values vary from \(-52.5606\) dB to \(-2.0855\) dB. The reason is \begin{table}
\begin{tabular}{c c} \hline \hline
**Method** & **Average Acoustic Contrast (dB)** \\ \hline ACC & 18.3381 \\ PM method in the bright zone & \(-0.5581\) \\ EDPM method in the bright zone & 0.8955 \\ Ours & 1.7317 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Average acoustic contrast comparison of four methods with respect to frequency. Figure 8: Acoustic contrast comparison diagram of four methods with respect to frequency variation. that the goal of the PM method in the bright zone is to reduce reconstruction error as much as possible and restore the original sound field in the bright zone. The EDPM method in the bright zone is an improvement of the PM method in the bright zone in solving algorithm, and they are similar methods. The ACC method does not pay attention to reconstruction error. Our method controls reconstruction error in the bright zone, so the reconstruction errors of our method are smaller than those of the ACC method. However, our method needs to control other factors in the sound field in addition to controlling the reconstruction error in the bright zone, so the reconstruction errors of our method are larger than those of the PM method in the bright zone and the EDPM method in the bright zone. The average reconstruction errors generated by four methods with respect to frequency are shown in Table 3. The average reconstruction error results generated by different methods are consistent with Figure 9. The average reconstruction error produced by the PM method in the bright zone is \(-17.8140\) dB, which is the smallest of all methods. The average reconstruction error produced by the ACC method is \(4.3408\) dB, which is the largest among all methods.