# User Visit Certification and Visit Trace System Using Inaudible Frequency
## 4 Experiments and Evaluations
With 50 attempts, 98% of the A space and 100% of the other spaces were certified, and with 100 attempts, 100% of both the A and B spaces were certified, while the C space was certified at 99% of the attempts. By demonstrating over 99% certification success in 10, 20, 50, and 100 certification experiments, we confirmed that the proposed method is available in many regions, even if 32 bits are used. After the visit certification, the information display for tracking a user's visit is presented in the form of a list, as shown in Figure 10, using the information stored in the SQLite database within the application. In Figure 10, the visit information is separated by the latest date, which appears in ascending chronological order. The user visited Waffle204 at 11:21:11 on Saturday, 24 August 2024, followed by Union Store at 14:52:33. The user visited A Twosome Place at 18:03:52, with the six-digit number next to the store name being the store ID. At this time, for ground truth, the user handwrote each store visited and the visit time on paper. As a result of comparing the value written by hand with the value saved by the application, we confirmed that each visit information and time match. When the user touches the \"Visit map\" button shown in Figure 10, the location of the visit certification using Google Maps 25.19.1 is displayed, as shown in Figure 11. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Times** & **A Space** & **B Space** & **C Space** \\ \hline
**10** & 100\% & 100\% & 100\% \\
**20** & 100\% & 100\% & 100\% \\
**50** & 98\% & 100\% & 100\% \\
**100** & 100\% & 100\% & 99\% \\ \hline \hline \end{tabular}
\end{table} 
Table 2: The experimental results of visit certification using the same trigger signal in different spaces. In Figure 11, Waffle204, Union Store, and A Twosome Place, which the user visited on Saturday, 24 August 2024, are displayed in pin form on Google Maps. Application users can easily trace their visits. In Figure 11, the user can return to the screen shown in Figure 10 by touching the \"Visit list\" button. Touching the \"Certification\" button shown in Figures 10 and 11 switches to the visit certification screen shown in Figure 6a, the initial screen of the application. Therefore, through visit certification accuracy experiments and visit certification time comparison experiments, the user visit certification and visit trace system proposed in this study was confirmed as a technology that can accurately and quickly certify electronic access to multi-use facilities. Thus, this technology will be useful for the untact services required by society after the COVID-19 pandemic. and higher accuracy when visitors to multi-use facilities certify their visits. Because the signal generation and processing used in the proposed method can be implemented with speakers installed in each store and web-based scripts, there are very few computational costs. The proposed method can only be used and saved after the application is installed on a smart device by those who want to save their location. In other words, in the case of the COVID-19 period, it can be installed and used on smartphones of people who need tracking, and there is a great need for the elderly with dementia in an aging society. In future studies, we will use the proposed application and server system to develop an epidemiological survey application that utilizes individual user visit histories stored in the server's database. In the experiment, 99.6% accuracy is provided for normal conditions. However, the noise or music distribution in the environment can mainly affect the characteristics if it has an effect in the range of 18 kHz to 20 kHz, and this situation can negatively affect the exchange. For this reason, we will conduct research and experiments to improve the performance in a noise-added environment of the proposed method. In addition, as in Section 4, \"Experiments and Evaluations,\" we conducted a visit certification experiment in five spaces of similar size.