# Bone Conduction Auditory Navigation Device for Blind People
## 5 Evaluation of the Proposed Navigation System
### Results and Discussion  
The trajectories of the induction paths in conditions 1, 2, and 3 are shown in Figure 13, whereas the times required to reach the goal are shown in Figure 14. First, in all three conditions, the subject can walk from point S to point G. However, for each condition and subject, the trajectories differ slightly from each other. As mentioned in the previous section, the subjects had a chance to practice walking the route and were quite familiar with the route. However, the subjects often became lost and were unable to reach their goals, as indicated by paths A, B, and C in Figure 13. For example, in the case of path A, the subject was slightly confused and eventually became lost. In the case of path B, the subject also became lost, but eventually reached his goal. However, in the case of path C, \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Warning Sound [deg.]** & \multicolumn{4}{c}{**Voice Guidance for Obstacles**} \\ \hline
0 & There is a &
\begin{tabular}{c} Person \\ Bicycle \\ \end{tabular} & within & 1 & meter. \\ \hline
30 & There is a &
\begin{tabular}{c} Person \\ Bicycle \\ \end{tabular} & within & 1 & meter. \\ \hline
330 & There is a &
\begin{tabular}{c} Person \\ Bicycle \\ \end{tabular} & within & 2 & meter. \\ \hline \hline \end{tabular}
\end{table} 
Table 10: Voice guidance for obstacle avoidance. the subject did not recognize the timing to turn right and eventually reached his goal via an incorrect route. Note that, at these points of becoming lost, the assistant following the subject guided the subject in the correct direction. The fact that the subjects are sighted and so are not accustomed to walking under \"blindness\" conditions may be one reason for the abovementioned confusion. Although some confusion was observed during navigation, the subjects could generally walk the route without any support by the assistant. The reason for this is that the information on the variation of the texture on the road surface obtained by the white can is of great use in blind walking. However, the time required to reach the goal largely varied depending on each condition. The time required for conditions 2 and 3, including information on obstacles with binaural sound reproduction, was largely shorter than that required for condition 1, in which only voice guidance was provided. In the case of subject 3, the order of the required time was not the same as those of the other subjects. In particular, the required time in the case of condition 1 is quite short. This is because, as mentioned previously, the subject failed to recognize the timing to turn right and followed an incorrect route. By comparing conditions 2 and 3, the required time for condition 3 was generally shorter than that for condition 2 in the case of subjects 1, 3, and 4. The reason for this is considered to be that the direction of the obstacle can be detected based of the binaural warning sound, and the subjects were able to walk without worry. Next, the subjective evaluation results are shown in Table 11. Comparing conditions 1, 2, and 3, the usability of the system is increased in conditions 2 and 3. In conditions 2  
Figure 14: Required time for each subject and condition. Figure 13: Walking paths of the four subjects from (**a–d**). and 3, the subjects reported that the binaural sound largely helped them to imagine the route (all of the subjects answered \"Yes\" for Q. 10). Due to the usage of the bone-conducted sounds with the ear of the subject open, all subjects answered \"Yes\" for Q. 7 and Q. 8, in which the convenience of the environmental sounds for detecting the circumstance of the surrounding environment is evaluated. As indicated by Q. 9, it was useful for all subjects to present a distance between the subject and other objects. In other questions regarding ease of adaptation for the system (Q. 1), the feeling of safety when using the system (Q. 2), and the total convenience obtained from the system (Q. 6), the average scores for condition 3 were the highest.