## 2 Materials and Methods
### admissible Road Traffic Noise Levels in the Slovak Republic
All intersections in the city of Michalovce were non-signalized four-arm intersections before reconstruction. At the mentioned intersections, a traffic survey was carried out at the same time as the noise load monitoring. The results (before and after reconstruction) of the traffic volume (veh/h) (vehicles entering the intersection) and the truck proportion \(p\) (%) are presented in the Table 2. Differences of up to 8% were found between the presented traffic volumes, which created a successful basis for correct comparison of noise load before and after the reconstruction of intersections. The basic characteristics of two roundabouts in Michalovce were diameters of \(D=31\) m, single lane widths of 5.5 m, and wearing course from asphalt concrete AC11 wear (Figure 2a,b). The third roundabout had a diameter of 62 m and two lanes on the circuit with a total width of 12 m and wearing course from asphalt concrete AC11 wear (Figure 2c). Another study of the impact on the noise load of the reconstruction of a three-arm intersection into a roundabout with a diameter of 36 m and a single lane width of 6 m in the vicinity of residential buildings took place in the city of Zilina (Figure 3). The reconstruction was carried out in 2016. The traffic noise emission measurements at the three-arm intersection were carried out in 2016 (T_16), and the measurements were carried out at two measuring stations: MS1 (29 June 2016, 8:45-9:45 a.m.) and MS2 (29 June 2016, 10:00-11:00 a.m.). The original three-arm intersection was located at the point where the industrial and recreational zones of the city of Zilina intersect with a built-up area of companies and recreation facilities and services. Traffic noise emission measurements at the new roundabout were carried out in 2017 (R_17). The measurements were carried out at the same measuring stations as used for the original three-armed junction: MS1 (28 June 2017, 8:45-9:45 a.m.) and MS2 (28 June 2017, 10:00-11:00 a.m.) (Figure 3). The main purpose of the presented reconstruction was to construct a safe, capable, and environmentally satisfactory crossroad as a traffic hub for \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Intersection**} & \multicolumn{2}{c}{**Before**} & \multicolumn{2}{c}{**After**} \\ \cline{2-5}  & **Traffic Volume (veh/h)** & _p (\%)_ & **Traffic Volume (veh/h)** & _p (\%)_ \\ \hline R1 & 1091 & 2.5 & 1006 & 2.6 \\ R2 & 1235 & 2.8 & 1156 & 2.6 \\ R3 & 885 & 3.8 & 903 & 3.6 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Hourly traffic volume and truck proportion at the intersections detected during noise load measurements in Michalovce City. Figure 3: Photos of the three-arm intersection before (**left**) and after (**right**) reconstruction into a roundabout and marked measuring stations and intersection arms in Zilina City. vehicles as well as for pedestrians and cyclists. The roundabout was built with a connection to existing residential and recreational territories and industrial areas of Zilina, significantly contributing to an increase in traffic safety in the location of interest. Another supplementary measurement was carried out at the roundabout at measuring stations MS1 (15 June 2022, 9:00-10:00 a.m.) and MS2 (15 June 2022, 10:15-11:15 a.m.) in 2022 after five years of use (R_22). During the measurements of the noise levels, the characteristics of the traffic flow (traffic volume, speed, and composition) were also monitored using radar counting devices (for more detailed information, see Section 2.5). Objetification of the Impact of the Reconstruction of Intersections into Roundabouts on the Noise Load in the Vicinity of Residential Buildings  
The presented traffic noise measurements for \(L_{Aeq}\) were attained with a sound analyzer (NOR-121, accuracy Class 0, Figure 4) with verification and calibration of the sound level meter, a measuring microphone (by the NORSONIC N-121 calibrator, accuracy Class 1), and one-third-octave filters.