## 4 Results and Discussion
### Comparison of Helmets
#### 4.3.2 Power Spectral Density in Alpha Waves
Finally, the power spectral density (PSD) was calculated and normalized for analysis. The tests were conducted on three young subjects, all women, aged between 19 and 21 years, as shown in Figure 43. These subjects were identified as 3, 4, and 5, maintaining continuity with the tests conducted in the previous subjects. \begin{table}
\begin{tabular}{l c c c c c} \hline \hline \multirow{2}{*}{**Helmet**} & \multirow{2}{*}{**Subject**} & **Mean PSD** & **SD PSD** & **Mean PSD** & **SD PSD** \\  & & **(Active State)** & **(Active State)** & **(Relax State)** & **(Relax State)** \\  & & \(\upmu\)V\({}^{2}\)/Hz & \(\upmu\)V\({}^{2}\)/Hz & \(\upmu\)V\({}^{2}\)/Hz & \(\upmu\)V\({}^{2}\)/Hz \\ \hline
**Ultracortex** & 1 & 7.89 & 6.74 & 11.45 & 8.73 \\  & 2 & 10.12 & 8.96 & 30.36 & 22.17 \\  & 3 & 6.56 & 4.12 & 6.63 & 4.30 \\
**Total Mean** & & **8.19** & **6.61** & **16.15** & **11.73** \\ \hline
**Chameleon** & 1 & 21.73 & 14.87 & 29.61 & 17.94 \\  & 2 & 7.02 & 10.85 & 32.27 & 23.80 \\  & 3 & 30.19 & 14.58 & 33.43 & 23.01 \\
**Total Mean** & & **19.65** & **13.43** & **31.77** & **21.58** \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Comparison of mean and standard deviation (SD) for power spectral density (PSD) in the 8–13 Hz range between Ultracortex and Chameleon helmets. Next, Figure 44 shows the graphs obtained for Subject 4. Figure 44: Normalized alpha PSD (8 to 13 Hz) for Subject 4 (**a**) with the Emotiv helmet, (**b**) with the Chameleon helmet. Figure 43: Healthy participants using the Emotiv headset during the experiment. As shown in Figure 44, the Emotiv headset had an average PSD of 0.08 \(\upmu\)V\({}^{2}\)/Hz in the active state and 0.21 \(\upmu\)V\({}^{2}\)/Hz in the relaxed state with a difference of 0.13 \(\upmu\)V\({}^{2}\)/Hz. On the other hand, the Chameleon headset recorded an average of 0.22 \(\upmu\)V\({}^{2}\)/Hz in the active state and 0.35 \(\upmu\)V\({}^{2}\)/Hz in the relaxed state, also obtaining a difference of 0.13 \(\upmu\)V\({}^{2}\)/Hz. For this case, it can be said that both headsets exhibited a quite similar behavior in differentiating between one state and the other. The results of Subject 5 are presented in Figure 45.  
As shown in Figure 45, the Emotiv headset had an average PSD of 0.12 \(\upmu\)V\({}^{2}\)/Hz in the active state and 0.20 \(\upmu\)V\({}^{2}\)/Hz in the relaxed state with a difference of 0.08 \(\upmu\)V\({}^{2}\)/Hz. On the other hand, the Chameleon headset recorded an average of 0.18 \(\upmu\)V\({}^{2}\)/Hz in the active state and 0.45 \(\upmu\)V\({}^{2}\)/Hz in the relaxed state, obtaining a difference of 0.27 \(\upmu\)V\({}^{2}\)/Hz. This shows a  
Figure 45: Normalized alpha PSD (8 to 13 Hz) for Subject 5 (**a**) with the Emotiv helmet, (**b**) with the Chameleon helmet. clear difference, indicating that the Chameleon headset can better distinguish between the two states. The results of Subject 6 are presented in Figure 46.  
As shown in Figure 46, the Emotiv headset had an average PSD of 0.14 \(\mathrm{\mu V^{2}/Hz}\) in the active state and 0.18 \(\mathrm{\mu V^{2}/Hz}\) in the relaxed state with a difference of 0.04 \(\mathrm{\mu V^{2}/Hz}\). On the other hand, the Chameleon headset recorded an average of 0.23 \(\mathrm{\mu V^{2}/Hz}\) in the active state and 0.30 \(\mathrm{\mu V^{2}/Hz}\) in the relaxed state, obtaining a difference of 0.07 \(\mathrm{\mu V^{2}/Hz}\). In this case, a small difference is observed in the measurements with the Chameleon headset showing a slightly higher value. In Table 6, the normalized mean PSD values and standard deviations (SDs) for the different subjects are presented in both helmets. Figure 46: Normalized alpha PSD (8 to 13 Hz) for Subject 6 (**a**) with the Emotiv helmet, (**b**) with the Chameleon helmet. The results in Table 6 reveal a similar trend between both devices, which was possibly influenced by the application of normalization.