## 4 Physical Experiment  
### Description of the Experiment and the Initial Data  
Measurements of the physical experiment were carried out on 3 March 2020. Measurements were performed at the picket 9 of the railway section Stasylos-State border (with Belarus), at 45.6 km, next to the existing ATLAS LG system. The measurement scheme is given in Figure 2.  
* Three cargo trains were measured. Two trains were traveling in the direction State border to Stasylos, and one train was traveling in the direction Stasylos to State border. * Air temperature +5 \({}^{\circ}\)C, wind speed 2 m/s;
* Measurement devices--ATLAS LG system and Bruel and Kjaer (Narum, Denmark) Type 9727 measurement equipment;
* General parameters registered by ATLAS LG:
* Train weight, t; number of wheelsets, pcs. ; train length, m; average load ratio; movement speed, m/s; train acceleration, m/s\({}^{2}\); train load, t/m; time and date. * Parameters of each wheelset registered by ATLAS LG:  
Figure 2: Measurement place diagram. * Number of axles; alarm signal; maximum force, kN; maximum reduced force, kN; load, t; speed, m/s; distance from the first wheel, m; acceleration deviation from the first wheelset, m/s\({}^{2}\); time from the first wheelset, s.
* Sound was measured using Bruel and Kjaer Type 9727 measuring equipment (Figure 3a). * It consists of Type 7910 software (Bruel and Kjaer. Naerum, Denmark); multichannel data storage unit Type PULSE 3560-B (Bruel and Kjaer. Naerum, Denmark); computer and microphones GRAS 46 AE 1/2\" CCP standard field microphone set (range of measured frequencies: 3.15 Hz to 20 kHz, dynamic range: 17 dB (A) to 138 dB [14]. * Sensitivity: 50 mV/Pa, IEC 61672 class 1); three microphones 186157, 190590 and 270029;
* Microphone layout diagram is given in Figure 4.  
Figure 4 shows:  
* Parameters measured by the equipment:
* Sound power, Pa; sound power level of the sound frequencies, dB and Hz. * Influencing factors/conditions were taken as a benchmark. Changes in sound pressure resulted from changes in wheel force, assuming that the additional factors/conditions remained constant, while only the force changes. Track condition data were acquired from JSC \"Lithuanian Railways\" (Vilnius, Lithuania). Rail conditions are presented in Table 1.  
Figure 3: Sound measuring equipment. (**a**) Bruel and Kjaer Type 9727 measuring equipment and (**b**) GRAS 46 AE 1/2′′ CCP microphone. \begin{table} \begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Category**} & **Allowed** & \multirow{2}{*}{**Rail Type**} & **Mounting** & **Sleepers** & \multirow{2}{*}{**Ballast**} \\  & **Speed, km/h** & & & **Type** & **Type** & **Type** \\ \hline III & 100/80 & R65 & \begin{tabular}{c} PANDROL \\ Fastclip \\ \end{tabular} & GB & crushed stone \\ \hline Last & \begin{tabular}{c} Jointed/ continuously \\ welded road \\ \end{tabular} & \begin{tabular}{c} Number of \\ defective \\ rails in \\ km/year \\ \end{tabular} & \begin{tabular}{c} Number of \\ defective \\ \% \\ \end{tabular} & \
\begin{tabular}{c} Number of \\ defective \\ sleepers, \% \\ \end{tabular} &
\begin{tabular}{c} Ballast \\ contamination, \% \\ \% \\ \end{tabular} \\ \hline
2007 &
\begin{tabular}{c} continuously \\ welded \\ \end{tabular} & 3 & 20 & 0 & \(\leq\)20 \\ \hline \hline \end{tabular}   
* Track profile data are also acquired from JSC “Lithuanian Railways” and indicated in Figure 5.  
\begin{table}