## 2 Materials and Methods  
A sandy gravel production plant (Figure 1) consisting of a crushing plant facility VL1, a gravel screening plant facility VL2 (containing three conveyor belts with hoppers for individual gravel and sand fraction dumps), and a gravel washing plant Pr was considered as a noise source. Residential areas of houses and the gravel production plant are located in flat terrain.  
Crushing plant VL1  
The opencast mining method using a floating bucket excavator is used for extracting raw material, which is then conveyed to a self-dumping barge by a conveyor belt. The barges are moved by push tugs along the lake's fairway to the harbor, where they are emptied into the water. Using a floating bucket elevator, the extracted raw material is loaded onto a conveyor belt, which transports it to the screening plant, where it is divided into over-sieve and under-sieve material. Over-sieve material is conveyed by a chute into the jaw crusher. The resulting fraction from the crusher and the under-sieve material are conveyed through chutes to two screeners, where the material is divided into two fractions. The first fraction is conveyed to an interdeck by means of conveyor chutes and belts. The second fraction is conveyed by means of conveyor belts and chutes for further processing--firstly, to two large-volume bins and from there to the cone crusher. The resulting product is conveyed by conveyor belts to the screener, where the over-sieve and under-sieve fractions are separated. The over-sieve fraction is conveyed for re-crushing and the under-sieve fraction is conveyed to the dump.  
Sandy gravel screening plant VL2  
VL2 is supplied from the interdeck. The material is transported by means of a conveyor belt running in a tunnel under the dump. It is further divided by a chute into a pair of screeners, which are used to sort the material into four fractions, each of which is deposited in a large-capacity dump.  
Water from the lake, transported by two pumps, is used for the screening of sandy gravel in the washing plant. Sludge water from the Pr washing plant is fed to a hydrocyclone, where the process water is separated from the usable particles. Usable particles are then transferred to a dewatering screen, which conveys them to a fraction conveyor belt, while the process water is discharged through a gutter to a sludge bed. The final sandy gravel is loaded onto trucks by loaders moving along marked routes.  
The sandy gravel production plant is located between two residential areas I and II (Figure 2).  
Figure 1: Sandy gravel production plant.  
Family houses in residential area I are located at 40-60 m from the sandy gravel production plant. Family houses in residential area II are located at 20 m from the sandy gravel production plant. Brüel & Kjaer measuring devices (see Table 1) were used to measure noise.  
\begin{table}
\begin{tabular}{l} \hline \hline
**Type** \\ \hline Briel \& Kjaer 2250-L Sound level meter and \\ handheld analyzer with built-in 1/1- and \\ 1/3-octave filters bands [15] \\ \hline [PERSON] \& [PERSON] 4189 Prepolarized free-field \\ microphone [16] \\ \hline [PERSON] \& [PERSON] 4230 Sound Level Calibrator [17] \\ \hline \hline \end{tabular}
\end{table}
Table 1: Equipment used for noise measurement.  
Figure 2: Production operation and residential areas.  
Based on the spectral composition of noise and orientation of the measuring microphone relative to the dominant noise source in accordance with [18], an expanded measurement uncertainty of U = 2.3 dB was determined. There are no significant tonal components in the frequency spectrum of the measured sound in the frequency range > 4 kHz, and the measuring microphone was oriented towards the noise source with a deviation of \(\leq\)30\({}^{\circ}\) from its reference axis.