# Measurements of Human Perception of Train Vibration
## 4 Measurement Results  
A comprehensive 24 h monitoring initiative was conducted to assess the impact of vibrations on individuals within a residential room close to the track which is the dynamic excitation. Following the standard [16] for ground vibration sources, a measurement point was selected, located in the structural center of the floor in a room located on the side of the force and intended for permanent stay of people. Additionally, it was the room with the largest ceiling span, which guarantees that the human perception of passive vibrations will be the highest in this room. The measurements were recorded in three orthogonal directions: X--the horizontal direction perpendicular to the input; Y--the horizontal direction parallel to the input, and Z--the vertical direction (see Figure 11).  
Figure 10: Types of trains passing next to the building.  
Figure 9: Measurement point in the center of the floor.  
Examples of recorded waveforms of vibrations in all three directions are shown in Figure 12. It is a registration of an old passenger train ride, as a result of the analysis of which the highest value of exceeding the comfort threshold was obtained, equal to 16.65. To illustrate the recorded vibration waveforms, the most intense horizontal components, x and y, as well as the vertical component z, recorded from the passage of an old type of passenger train, were selected (see Figure 12). The maximum value of the acceleration of the vertical z component of vibrations is particularly noteworthy. The maximum acceleration value for this component is 66.22 cm/s\({}^{2}\). The maximum acceleration values of the horizontal x and y components of the vibrations are significantly smaller (see Figure 12). Such a high value of the acceleration of the vertical z component of the vibrations is due to the flexibility of the wooden ceiling structure and the distance of the building from the railway tracks.  
Figure 11: The location and directions of the measurement point (P-04x sensor for registration vibration in perpendicular direction; P-05y—sensor for registration vibration in parallel direction; P-06z sensor for registration vibration in horizontal direction).  
Figure 12: Examples of waveforms of vibration in three directions.  
After recording the vibration waveforms, the RMS procedure was carried out to assess the impact of vibrations on the building residents. In Figure 13, examples of RMS, made from waveforms shown in Figure 12, are summarized. In the vertical z component of vibrations, frequencies from the 8 to the 12.5 Hz band dominate (see Figure 13). In the horizontal x component of vibrations (the \(x\)-axis is perpendicular to the railway tracks), higher components from the 40 to the 63 Hz band dominate. A lower frequency band ranging from 8 to 10 Hz can also be distinguished. On the other hand, in the horizontal y component of vibrations (the \(y\)-axis is parallel to the direction of the railway tracks), dominant frequency bands of 12.5 and 40 to 63 Hz can be distinguished (see Figure 13).  
Figure 13: Examples of RMS analysis in three directions.  
Out of the 87 dynamic events, the perception threshold of vibrations was surpassed in 50 instances. Furthermore, in seven of these cases, the vibrational comfort level was also exceeded (see Table 2)  
The maximum value of the WODL coefficient reached 16.6, observed within a frequency band of 10 Hz. As evident from Table 2, nearly every type of train resulted in the exceedance of the comfort level according to the Polish Standard [16] (refer to Table 3).  
As evident from Table 3, nearly every type of train resulted in the exceedance of the comfort level. To facilitate predictions, leveraging the substantial dataset, a decision was made to conduct a nonlinear regression analysis.