## 4 Performance Testing
### Anti-Noise Test  
According to Table 2, different noise backgrounds corresponded to different decibels. Therefore, in order to study the anti-noise performance of the novel vehicle terminal, noise tests were carried out in noise environments respectively such as 60, 70, 85, 95, 100, and 110 dB, and some data are shown in Tables 3 and 4. In order to compare all data visually, the success rate for different decibels was measured at different measurement distances, as shown in Figure 9.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Decibel** & **Environmental Characteristics** \\ \hline
15 dB below & Feel quiet \\
30 dB & Whisper of volume \\
40 dB & The buzz of the fridge \\
60 dB & Normal conversation sound \\
70 dB & Walk in the downtown area \\
85 dB & Car on the road \\
95 dB & Starting sound of motorcycle \\
100 dB & The sound of the electric drill \\
110 dB & The sound of [PERSON] OK or loudly play MP3 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Correspondence between factual environment and noise decibel degree.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Test Distance** & **Press Times** & **Success Times** & **Success Rate** \\ \hline
5 cm & 20 & 19 & 100\% \\
30 cm & 20 & 20 & 100\% \\
50 cm & 20 & 20 & 100\% \\
100 cm & 20 & 20 & 100\% \\
120 cm & 20 & 17 & 85\% \\
130 cm & 20 & 17 & 85\% \\
140 cm & 20 & 16 & 80\% \\
150 cm & 20 & 14 & 70\% \\
180 cm & 20 & 10 & 50\% \\
200 cm & 20 & 2 & 10\% \\ \hline \hline \end{tabular}
\end{table}
Table 1: Success rate under quiet environment.  
It can be seen from Figure 9 that the success rate was higher than 95% at the effective distance of 1 m with different noise. This shows that the frequency distribution and the degree of decibel in different environments were different. However, under the effect of the modulation/demodulation algorithm, the double acoustic wave enhancement algorithm and other noise reduction measurement, the influence was reduced significantly.  
\begin{table}
\begin{tabular}{c c c c} \hline
**Test Distance** & **Press Times** & **Success Times** & **Success Rate** \\ \hline
5 cm & 20 & 20 & 100\% \\
30 cm & 20 & 20 & 100\% \\
50 cm & 20 & 20 & 100\% \\
100 cm & 20 & 20 & 100\% \\
120 cm & 20 & 18 & 90\% \\
130 cm & 20 & 17 & 85\% \\
140 cm & 20 & 17 & 85\% \\
150 cm & 20 & 15 & 75\% \\
180 cm & 20 & 10 & 50\% \\
200 cm & 20 & 2 & 10\% \\ \hline \end{tabular}
\end{table}
Table 4: Success rate under a noise environment of 110 dB.  
Figure 9: Statistics of success rate under different decibel degrees and measurement distances.  
From the data in Table 3, Table 4, or Figure 9, it could be seen that the success rate decreased beyond the effective distance of 1 m, but the trend of the success rate in different noise environments was almost identical. This shows that the reason for the decay of success rate was affected by the test distance instead of the noise condition.  
In summary, the vehicle terminal for the time-sharing rental electric vehicle based on acoustic communication technology had a high anti-noise ability, which could adapt to a variety of noise environment, to ensure the fluency and integrity of the whole time-sharing rental business process to lay a solid technical support.