## 2 Materials and Methods
### admissible Road Traffic Noise Levels in the Slovak Republic  
Although this article only mentions the traffic noise effects on the outdoor environment of residential buildings, the authors consider the outdoor environment to be an integral part of the buildings. The public generally perceives traffic noise as having the most disturbing influence on the quality of the external environment, and it can be concluded with a high degree of probability that noise from road traffic is a limiting factor in the quality of housing. In strategic noise mapping and noise studies, traffic noise is evaluated separately for reference time intervals: daytime is from 6 a.m. until 6 p.m., evening is from 6 p.m. until 10 p.m., and night-time is from 10 p.m. until 6 a.m. The decisive codified provisions regarding the method of determining the admissible limits of traffic noise in the external environment (Table 1) and the indoor environments of buildings are presented in [47]. This Decree of the Ministry of Health of the Slovak Republic [47] states that the protection of public health against traffic noise is ensured if the quantities of noise for the day, evening, and night are not higher than the noise limits presented in Table 1. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & & & & & **Admissible Values (dB)** \\ \hline \multirow{3}{*}{**Territory Category**} & \multirow{3}{*}{**Description of the Outdoor Environment**} & \multirow{3}{*}{**Time Interval**} & \multicolumn{3}{c}{**Traffic Noise**} \\  & & & **Road and Water** & **Railways** & **Air Transport** \\  & & & **Transport \(L_{Avg,a}\)** & \(L_{Avg,a}\) & \(L_{Avg,a}\) & \(L_{Avg,a}\) \\ \hline \multirow{3}{*}{**II.**} & Areas in front of windows of residential rooms; protected rooms, such as school buildings, medical facilities, and other protected buildings; and outdoor territories in residential and recreational areas & **avg** & **50** & 50 & 55 & - \\  & & & **weight** & 45 & 45 & 45 & 65 \\ \hline \multirow{3}{*}{**III.**} & Areas in category II near motorways and roads of classes I and II, local public transport roads, railways, airports, and city centers & **avg** & **60** & 60 & 60 & - \\  & & & **weight** & **50** & 55 & 50 & 75 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: The traffic noise admissible (a) values for selected outdoor territory categories around residential buildings [47]. Figure 1: Frequency weighting characteristics for the assessment of human exposure to noise [49]. Admissible values for the noise level in the indoor environments of buildings [47] are defined in the following way. The determining factor for indoor building environments is the maximal \(A\) sound level \(L_{Amax}\) or the equivalent \(A\) sound level \(L_{Aeq}\). Admissible values for the noise level in indoor environments of residential buildings from external sources according to [47] are 40 dB for the day and evening, and 30 dB for the night. Study Area Used for the Reconstruction of Non-Signalized Intersections into Roundabouts from the Aspect of Noise Pollution  
As part of this contribution, we focused on four intersections that were transformed from non-signalized intersections into roundabouts in Michalovce City and Zilina City from the point of view of the change in road-traffic-related noise emissions. Photos of the intersections before and after reconstruction from non-signalized intersections into roundabouts (R1-R3) are presented in Figure 2. In the outdoor environment of residential buildings in Michalovce in the period 2007-2012 (day of measurements are specified in Section 3.1), the following intersections were reconstructed:  
* Stefanikova-Salezianov-Martina Razusa streets (R1);
* Stefanikova-Okruzha-Jana Svermu streets (R2);
* Jana Holleho-Moskovska-Okruzha--Lastomirska streets (R3). Figure 2: Photos of the intersections (**a**) R1, (**b**) R2 and (**c**) R3 before (**left**) and after (**right**) reconstruction to roundabouts in Michalovce City.