## 3 Results and Discussion
### Noise Measurement in Residential Areas  
Noise values measured at residential area I (houses A, B and C) and residential area II (houses D, E and F), location of which can be seen in Figure 4, are listed in Table 3. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Measuring Point** & **L\({}_{\text{eq,A}}\) [dB]** & **Altitude [m]** & **L\({}_{\text{Aeq,p}}\) [dB]** \\ \hline
1 & 87.1 & 191.3 & \\
2 & 83.0 & 191.3 & \\
3 & 73.9 & 181.2 & \\
4 & 84.9 & 200.9 & \\
5 & 88.5 & 200.7 & \\
6 & 68.9 & 178.9 & \\
7 & 63.5 & 178.9 & \\
8 & 62.4 & 178.9 & 70.0 \\
9 & 59.7 & 178.9 & \\
10 & 68.4 & 178.9 & \\
11 & 76.6 & 199.6 & \\
12 & 88.7 & 178.9 & \\
13 & 73.4 & 178.9 & \\
14 & 71.2 & 178.9 & \\
15 & 70.6 & 178.9 & \\
16 & 62.7 & 178.9 & \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Noise values measured at the sandy gravel production plant. Figure 5: Measuring points at the sandy gravel production plant. The permissible noise level in residential areas I and II in accordance with [19] is L\({}_{\text{Aeq,P}}\) = 50.0 dB. One of the factors contributing to exceeding of permissible noise level in residential areas I and II was ambient noise significantly affecting the resulting noise level. The results of measurements confirmed that noise levels were exceeded in the sandy gravel production plant as well as in residential areas (Tables 2 and 3). Research on the Effectiveness of Selected Noise-Reducing Measures in the Sandy Gravel Production Process  
As part of the research into noise abatement options, measures for achieving the reduction of noise levels were proposed. Individual measures were planned to be implemented in a phased manner, with continuous monitoring of whether, and at what level, the noise would be reduced to the required level. The design of individual measures was based on an assessment of their feasibility and took into account that they would reduce noise from individual noise sources. The measures have been designed in such a way that they were expected to have at least a partial effect, that they would not significantly affect the technology used or restrict existing production in any way. Based on the above criteria, it was decided that the research would cover three types of measures:  
* modernization of machinery--the measure assumed that new or modernized machinery produces lower noise levels than the original one. This was based on the assumption that the original equipment had worn-out components, which thus emit excessive noise as a result of their mechanical wear and tear. No such deficiency was anticipated for new machinery. * noise barrier--for noise barriers it was assumed that the absorbing capacity of the material would be used to reduce the level of reflected sound. Primarily, use of porous materials was assumed here for the scattering of acoustic energy within their thickness. In case the solution proved ineffective, the use of membranes and resonators has also been planned. * traffic routes--when modifying traffic routes, it was considered to replace mechanical parts of the equipment which, due to their wear could be a source of noise. Another proposed solution has been the replacement of mechanical parts such as rollers with others that were declared to have reduced noise levels. All of the above measures were implemented in a phased manner, with ongoing monitoring of noise levels. At the same time, the research was coordinated on the basis of [22]. The first stage of noise reduction research concerned the attenuation of noise from the jaw crusher. Based on this, the following feasible measures have been proposed:  
* walling of the jaw crusher,
* enclosure of production facilities on three sides (site entrance, lake, residential area II). Results obtained from this initial stage of the research are shown in Table 4. It can be observed that the measures have resulted in noise reduction, but the required level below 50 dB has not been achieved. On this basis, the measures were assessed as insufficient, and the second stage of research was proceeded with.