## 3 Test Data Analysis
### Frequency Response Transfer Analysis  
#### 3.4.1 Vibration-Level Transfer Analysis  
In order to analyze the frequency-division vibration-level transfer characteristics of the rail, the track bed and the tunnel wall under the four working conditions, the vibration-level transfer difference and the vibration-level transfer rate of the rail-track bed, track bed and tunnel wall are compared and analyzed, as shown in Figures 20 and 21. Among them, the vibration-level transfer difference is the difference between the frequency-division vibration levels of each frequency band of the rail-track bed, track bed-tunnel wall, and the vibration-level transfer rate is the frequency-division vibration-level ratio of the track bed-rail, tunnel wall-track bed. It can be seen that the vibration-level transmission difference is inversely proportional to the transfer rate, that is, if the vibration-level transmission difference between adjacent track components is larger, the transfer rate is correspondingly smaller.  
According to Figures 20a and 21a, it can be seen that for the vibration-level transfer between the rail and the track bed, the vibration-level reduction of the steel-spring-floating slab track is small, that is, the vibration-level transfer rate is large. Especially in the vibration level in the 12.5-100 Hz frequency band, the vibration-level transfer rate is generally around 0.9. However, the rail-track bed vibration-level transfer difference of the ordinary monolithic track is generally larger than that of the steel-spring-floating slab track, and the vibration-level transfer rate of each frequency band is mostly between 0.6 and 0.75, and the vibration-level transfer rate gradually decreases as the frequency increases. At the same time, through the comparison between the straight line segment and the curved segment, it can be seen that for the frequency band above 400 Hz, the vibration transmission of the rail-track bed in the curved segment is significantly greater than that in the straight line segment.  
According to Figures 20b and 21b, it can be seen that for the vibration-level transfer between the track bed and the tunnel wall, the vibration level of the steel-spring-floating slab track is greatly reduced, that is, the vibration-level transmission rate is low, and the vibration level of each frequency band has dropped significantly. However, the vibration  
Figure 19: Comparison of frequency-division vibration-level insertion loss.  
level transfer difference between the track bed and the tunnel wall of the ordinary monolithic track is generally smaller than that of the steel-spring-floating slab track. In the frequency above 10 Hz, the vibration-level transfer rate is larger. The reason is that the ordinary monolithic track and the shield tunnel are consolidated by reinforced concrete, so the vibration transmission is equivalent to a whole structure, so the vibration level reduction is small and the vibration-level transmission rate is large. At the same time, it can be seen from the comparison between the straight line segment and the curved segment that the vibration-level transfer rate of the steel-spring-floating slab track in the segment below 10 Hz is greater than that of the ordinary monolithic track. The vibration-level transfer rate of the steel-spring-floating slab track in each frequency band of the straight line and the curved segment is very close, while the vibration level transmission of the ordinary monolithic track at high frequencies is smaller than that of the straight line segment.