# Measurement and Analysis of Vibration Levels for Truck Transport Environment in Korea
## 4 Conclusions  
To analyze the vibration levels occurring in the truck transport environment in Korea and to develop composite PSD profiles for their lab-based simulation, three representative trucks and a test route were selected. The vibration signals obtained through the truck transportation test were analyzed in three classes, and the composite PSD profile was developed by dividing it into high and low levels. Comparing domestic transport vibration levels with those presented by international standards (ASTM: West Conshohocken, USA, ISTA: Chicago, USA) shows similar trends in the low frequency band, but as frequency increases, differences in PSD levels have occurred. This is a characteristic of highways in Korea, which is judged as a lack of straight roads. It is also possible to simulate the domestic transportation environment by applying PSD vibration level in Korea. The results of this study are summarized in the following points. 1. The vertical overall rms G values in the frequency range of 1\(\sim\)250 Hz were approximately 2.6 and 3.0 times higher than those of the lateral and longitudinal directions, respectively. 2. The value of the first PD level peak of the air-ride truck, which occurs as the suspension's response to external forces in the low-frequency region, was about two times smaller than that of the leaf-spring truck. Moreover, its frequencies were approximately 3 Hz and 1.5 Hz in the leaf-spring and air-ride trucks, respectively. \begin{table} \begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Breakpoint No.**} & \multicolumn{6}{c}{**Leaf-Spring Truckfor the Lower 70\% of the Data Recorded**} \\ \cline{2-9}  & **Frequency (Hz)** & **PSD (G\({}^{2}\)/Hz)** & **dB** & **Oct** & **dB/oct** & **Area** & **Grms** \\ \hline
1 & 1 & 0.001 & - & - & - & - & - \\
2 & 2 & 0.007 & 8.45 & 1.00 & 8.45 & 0 & 0.06 \\
3 & 4 & 0.007 & 0 & 1.00 & 0 & 0.02 & 0.13 \\
4 & 6 & 0.0015 & \(-\)6.69 & 0.58 & \(-\)11.44 & 0.02 & 0.16 \\
5 & 15 & 0.0015 & 0 & 1.32 & 0 & 0.04 & 0.19 \\
6 & 22 & 0.0001 & \(-\)11.76 & 0.55 & \(-\)21.29 & 0.04 & 0.20 \\
7 & 30 & 0.0001 & 0 & 0.45 & 0 & 0.04 & 0.20 \\
8 & 40 & 0.0007 & 8.45 & 0.42 & 20.36 & 0.05 & 0.21 \\
9 & 50 & 0.0007 & 0 & 0.32 & 0 & 0.05 & 0.23 \\
10 & 80 & 0.0001 & \(-\)8.45 & 0.68 & \(-\)12.46 & 0.06 & 0.25 \\
11 & 100 & 0.0001 & 0 & 0.32 & 0 & 0.06 & 0.25 \\
12 & 130 & 0.0003 & 4.77 & 0.38 & 12.61 & 0.07 & 0.26 \\
13 & 210 & 0.0003 & 0 & 0.69 & 0 & 0.09 & 0.30 \\
14 & 250 & 0.0002 & \(-\)1.76 & 0.25 & \(-\)7.00 & 0.10 & 0.32 \\ \hline \hline \end{tabular} 
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Breakpoint No. **} & \multicolumn{6}{c}{**Air-Ride Truckfor the Lower 70\% of the Data Recorded**} \\ \cline{2-9}  & **Frequency (Hz)** & **PSD (G\({}^{2}\)/Hz)** & **dB** & **Oct** & **dB/oct** & **Area** & **Grms** \\ \hline
1 & 1 & 0.0015 & - & - & - & - & - \\
2 & 2 & 0.0032 & 3.29 & 1.00 & 3.29 & 0 & 0.05 \\
3 & 4 & 0.0003 & \(-\)10.28 & 1.00 & \(-\)10.28 & 0 & 0.07 \\
4 & 12 & 0.0003 & 0 & 1.58 & 0 & 0.01 &  
The vertical overall rms G value for the top 30% of the data recorded in the frequency range of 1\(\sim\)250 Hz was approximately 0.31 G for the leaf-spring truck and 0.18 G for the air-ride truck; that for the lower 70% of the data recorded was approximately 0.18 G and 0.08 G, respectively. 4. In the low-frequency range of 1\(\sim\)10 Hz, the shape of the high-level PSD profile of leaf-spring truck, representing the top 30% of the data recorded was roughly similar to that of ASTM D4169:16 (medium level), ISTA 3A (over-the-road trailer spectrum) and other studies but differed significantly in the higher-frequency region. Also, the shape of its PSD profile of the air-ride truck was roughly similar to that of the ISTA 3H (air-ride suspension truck) but also differed significantly in the higher-frequency region. 5. As the travel speed increased, the truck vibration level increased, although the increase rate of the air-ride truck was more significant than that of the leaf-spring truck.