## 4 Test Results and Analysis
### Hanger Appearance Inspection  
Based on the test results in Table 3, there are significant differences in vibration intensity at different positions and travel speeds. The vibration intensity is more sensitive to the change in travel speed due to the influence of the \"shock effect\". On the other hand, the energy density generated by vehicle vibration is attenuated during propagation, so the farther away from the vibration source, the smaller the vibration intensity of the measuring point.  
Figure 4 gives each measuring point's horizontal vibration velocity curves at different travel speeds. As shown in Figure 4, the vibration intensity caused by road traffic gradually attenuates with the increased distance from the vibration source. The vibration velocity attenuates extremely quickly at close range and then tends to be flattened when the distance exceeds 20 m. The influence of travel speed is mainly reflected at close range, while the travel speed has little effect for long-distance vibration.  
It should be noted that the 70 m distance does not only consist of noise signals. The amplitude of vibration velocity at a distance of 70 m is 10\({}^{-1}\) mm/s, but the vibration caused by noise typically ranges from 10\({}^{(-2\text{ to }-3)}\) mm/s. There is little association between the 70 m vibration velocity and the traveling speed. Nevertheless, the impact is minimal. Furthermore, the authors thoroughly reviewed the existing literature on environmental vibration, specifically focusing on the positioning of measurement sites. Surprisingly, no mention was found of the issue of noise at measurement points. For example, [PERSON] et al. [43] measured noise after a sociological survey on Shinkansen noise. Noise levels were measured on many occasions at reference positions close to the Shinkansen line, along with distances  
\begin{table}
\begin{tabular}{c c c} \hline
**Working Condition No.** & **Travel Speed (km/h)** & **Number of Tests** \\ \hline
1 & 10 & 3 \\ \hline
2 & 20 & 3 \\ \hline
3 & 40 & 3 \\ \hline
4 & 60 & 3 \\ \hline \end{tabular}
\end{table}
Table 2: Test conditions.  
\begin{table}
\begin{tabular}{c c c c c} \hline
**Measurement** & \multicolumn{4}{c}{**Peak Vibration Response (mm/s)**} \\
**Point Number** & **10 km/h** & **20 km/h** & **40 km/h** & **60 km/h** \\ \hline
1 & 0.719 & 1.923 & 5.164 & 6.671 \\
2 & 0.404  
of 5, 10, 20, 40, and 80 m from these reference points. [PERSON] et al. [44] gathered data at reference sites near the Shinkansen line at distances of 5, 10, 20, 40, and 80 m from these reference points. [PERSON] et al. [45] placed observation locations at distances ranging from 15 m to 70 m from the centerline of the track, making use of the safety guardrails for protection. [PERSON] & [PERSON] [46] performed vibration measurements to address the issues of environmental vibration and environmental noise pollution. The noise levels of passing railroad trains were recorded at distances of 0, 10, 20, 40, 80, and 160 m from the reference location.  
The time-history curves of the ground vibration response of each measuring point at different travel speeds are shown in Figure 5.  
As seen in Figure 5, for the same travel speed, the horizontal vibration velocity response decreases with the increase of the vibration source distance. In addition, due to the time-sensitive vibration propagation, there is an obvious \"vibration hysteresis\" phenomenon for long-distance vibration. Heavy vehicles should slow down as much as possible and keep away from cultural relics in actual projects.  
Figure 4: The vibration response of different travel speeds.  
Figure 5: _Cont._