## 4 Discussion  
Almost all researchers in this field have tried to promote the efficiency of their aBCI systems through various methods [17; 41; 45; 47; 48]. So, improving the efficiency of our aBCI is a primary task in the study as well. The accuracy of an aBCI system is deeply affected by three primary factors. First, is the stimulus appropriate? Second, are the positions of electrodes to obtain the brainwave data appropriate? Finally, should the system select which ERP components (N2P3, P300, and N200) to interpret the data of the user's brainwaves online to achieve the best system efficiency? Related research has sprung up like mushrooms after rain to solve the above problems. We reviewed several studies similar to this one to discuss their strengths and weaknesses, as shown in Table 14. The further discussion showed in the text description after the table. Because of human hearing function, two factors affect the performance of the BCI system: whether the target sound stimulus attracts the user's attention and whether the user can easily distinguish the target sound stimulus from the non-target stimuli. The work of [PERSON] et al. also showed that performing an attention task in an intermittent noisy or silent room had different results. It could be that humans are unaware of all the noise surrounding them every second, but if we deprive them of it, it can be worse [21]. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multicolumn{6}{c}{**Dependent Variable: Average Bit-Rate**} \\ \hline
**Components** & **T3** & **T4** & **Fz** & **Cz** & **Pz** & **NN Technology** \\ \hline N200 & 0.0114 & 0.0345 & 0.0977 & 0.0585 & 0.0104 & 0.1401 \\ P300 & 0.0781 & 0.0477 & 0.0363 & 0.0563 & 0.0808 & 0.2123 \\ N2P3 & 0.1585 & 0.1401 & 0.1782 & 0.2260 & 0.2353 & 0.4418 \\ \hline \hline \end{tabular}
\end{table} 
Table 13: Comparison of the bit-rate of three ERP components (N2P3, P300, and N200). \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multicolumn{6}{c}{\(\alpha\) = 0.01, N = 340 for Boys and 140 for Girls} \\ \hline
**Components** & **Electrode** & **Case** & **_T-Value_** & **_p-Value_** \\ \hline N200 & T3 & boys vs. girls & \(-1.193\) & 0.246 \\  & T4 & boys vs. girls & \(-0.327\) & 0.746 \\  & Fz & boys vs. girls & \(-4.405\) & 0.000 *** \\  & Cz & boys vs. girls & \(-2.348\) & 0.028 * \\  & Pz & boys vs. girls & \(-2.116\) & 0.045 * \\  & NN & boys vs. girls & \(-1.398\) & 0.176 \\ \hline P300 & T3 & boys vs. girls & \(0.564\) & 0.590 \\  & T4 & boys vs. girls & \(-1.284\) & 0.212 \\  & Fz & boys vs. girls & \(0.586\) & 0.564 \\  & Cz & boys vs. girls & \(1.328\) & 0.226 \\  & Pz & boys vs. girls & \(0.973\) & 0.341 \\  & NN & boys vs. girls & \(0.709\) & 0.486 \\ \hline N2P3 & T3 & boys vs. girls & \(0.983\) & 0.336 \\  & Fz & boys vs. girls & \(-0.203\) & 0.841 \\  & Cz & boys vs. girls & \(-1.788\) & 0.088 \\  & Pz & boys vs. girls & \(0.201\) & 0.842 \\  & NN & boys vs. girls & \(-1.303\) & 0.206 \\ \hline \hline \end{tabular}
\end{table} 
Table 12: Independent samples t-test results of all trials between girls and boys. \begin{table}
\begin{tabular}{p{113.8 pt} p{56.9 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt}} \hline \hline
**References** & **Stimulation Modality** & **Electrodes** & **Subjects** & **Advantages** & & **Drawbacks** \\ \hline
[46] & P300 & Cpz, Poz, P3, P4, P5, P6, Cz, P2 in virtual sounds & Cpz, Poz, P3, P4, P5, P6, Cz, P2 in 10/10 & 9 HS & Both stimuli types generate different event-related potential response patterns allowing for their separate classification. & 1. & Too few people participated in the experiment. 2. & This analysis was more complicated, based on 8 electrodes. \\ \hline
[48] & P300 & F3, Fz, F4, T7, C3, Cz, C4, T8, Cp3, C4, P3, P2, P4, P07, PO8, Oz & F3, Fz, F4, T7, C3, P2, P4, P07  
and repeat the keywords in the stories. In our previous work [14], we invited seven participants familiar with a BCI system to test our aBCI system.