## 2 Shopping Center Noise Predictions
### Buildings Modelling  
The vectorised model of the commercial centre building was made according to the construction drawings provided by the constructor (the height regimes, walls material and the number and positions of the noise sources). As can be seen in the zoomed section of Figure 1, on the roof of the commercial centre, there are nine noise sources (eight air conditioners, model RV4B0909, each one having a sound power level of 62 dB(A) and a dry cooler, GFW 090.1/2-S(L)-F4/01/6P, with a sound power level of 75 dB(A). These sound power levels were taken from the technical specifications of the cooling systems that were provided by the constructor. In the prediction software, these cooling systems were modelled as point sources which radiate noise as a monopole source. The tenth noise source is represented by the supply ramp which is also considered as a point source, for which a sound power level of 90 dB(A) was defined.  
For each residential building, the number of inhabitants has been defined depending on the number of apartments from that building. The predictions performed in this study do not take into account the traffic and other noise sources, the only noise sources being represented by the loading/uploading activities generated only in the day period and the cooling systems that function continuously.  
This study presents 5 scenarios in which various methods of reducing the noise are studied. The first scenario presents the worst case, with the prediction of the noise generated by all sources and with no barriers. In the second scenario, an acoustic barrier at 2.3 m height is designed to screen the noise from the supply ramp. The third scenario presents an improved acoustic barrier with a bigger height of 4 m, whose geometrical parameters are presented in Figure 3. Both sound barriers from the second and third scenario consist of a sandwich panel with a perforated metal sheet, fibrous material and an unperforated metal sheet. For the sound barrier, the absorption coefficient was set to 0.6 only for the interior part of it and a transmission loss of 30 dB. The barrier was placed at a distance of L = 8.5 m, parallel with the supply ramp in order to permit the entrance of the supply van. For a better noise masking effect for the apartments at upper floors, in the third scenario, a sloped barrier was studied with the following parameters: height of the barrier Z = 4 m, and the height and the length of the sloped portion of the barrier dH, dV = 1.5 m, as is presented in Figure 3.  
Figure 2: Equivalent continuous sound pressure level (LAeq) at the building’s facade before building the shopping centre (red bars and dotted line: day period, black bars and dotted line: night period).  
In the fourth scenario, a closed construction made by sandwich panels with a perforated aluminium sheet on one side and mineral wool inside is constructed to insulate the noise generated by the supply ramp. Thus, the supply van will enter in this closed enclosure provided with a sliding door, that will reduce the noise propagation. For this sandwich panel, a sound transmission loss of 30 dB was set in the software. It must be mentioned that the supply activities are performed only in the day period (after 7:00). The fifth scenario completes the fourth scenario by adding sloped barriers next to the cooler units, thereby aiming to reduce also the noise generated in the night period by these cooling systems. Figure 4 presents all the scenarios and the proposed technical solutions to reduce the noise propagation.  
Figure 4: _Cont._  
Figure 3: Barrier design and location (barrier components: **A**—perforated metallic sheet, **B**—porous material, **C**—unperforated sheet; **D**—the supply ramp modelled as a point source, **E**—commercial centre wall, **L**—distance between barrier and commercial wall).