# Impact of Environmental Factors on Passenger Ride Comfort
## 7 Results of Experimental Studies
### Acoustic Comfort Results  
Figure 14 shows the results of noise measurements in the two specified types of metro trains and the passenger car on two surfaces. Based on the measurements of instantaneous sound levels, the A-curve-corrected equivalent sound level LAeq (noise level) was calculated. Measurements in the metro trains were conducted under typical operating conditions at a speed of approximately 40 km/h, while for the car, measurements were taken on a main road at a speed of 90 km/h and on a local road at 50 km/h.  
The results of the noise measurements show significant differences in sound levels for the different modes of transport. The older metro trainset generates a significantly higher noise level of 82.6 dB(A), indicating a greater noise nuisance compared to the new trainset, which reaches 77.6 dB(A).  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Comfort Index** & **Car, Main Road** & **Cat, Local Road** & **Metro, New Train** & **Metro, Old Train** \\ \hline \(a_{w}\) & 0.158 & 0.126 & 0.016 & 0.031 \\ \(a_{w}\) & 0.050 & 0.198 & 0.066 & 0.069 \\ \(a_{w}\) & 0.143 & 0.528 & 0.023 & 0.070 \\ \(a_{w}\) & 0.219 & 0.577 & 0.072 & 0.103 \\ Comfort level C1 & 5 & 4 & 5 & 5 \\ \hline \hline \end{tabular}
\end{table}
Table 9: Weighted RMS accelerations in the \(x\), \(y\), and \(z\) directions, the synthetic ride comfort index \(a_{w}\) according to the ISO 2631-1 standard, and the index of vibrational comfort C1 in the passenger car and metro trains.  
For the tested car, the noise level of 73.5 dB(A) was measured in the car cabin while driving on the main road. This value of LAeq is relatively lower compared to a local road with a poorer surface where the noise level of 81.6 dB(A) was recorded. These results suggest that the condition of the road surface has a significant impact on noise levels: a rough local road significantly increases noise emissions compared to a main, better-maintained route. Table 10 shows the results of the acoustic comfort level C2.  
Both the car driving on a local road and the old metro train received a score of 2 on the comfort scale, indicating noticeable acoustic discomfort. This is due to the poorer quality of the local road surface and the older design of the metro train, respectively. In contrast, the new metro train and the car on the main road scored slightly better at levels 3 and 4, classifying themselves as \"quite uncomfortable\" and \"slightly uncomfortable\". These results indicate that, despite the moderate noise annoyance, there is still a need to improve acoustic comfort in both new and older vehicles.  
The results of measurements in the present work show significant differences in noise levels between old and new metro trains, with older trains generating higher noise at 82.6 dB(A) compared to 77.9 dB(A) for the new metro train. The study for the Montreal metro [30] assesses acoustic and other types of comfort on a scale from 0 to 1, where 1 represents the highest level of comfort. For noise in the Montreal metro, old cars score 0.60, while new cars perform slightly better at 0.70, which correspond to noise levels in the intervals 65 dB < LAeq \(\leq\) 70 dB and 60 dB < LAeq \(\leq\) 65 dB, respectively. These levels are considerably lower than the noise levels measured in the present study in both old and new trains of the Warsaw metro.