## 3 Results and Discussion  
As already mentioned, many studies [31; 32; 33] state that LFN is a nonintrusive sound, and that employees become used to it over a long period of time. In contrast, many studies [1; 2; 3; 10; 11; 12; 13; 14; 15; 16; 17] consider LFN as one of the risk factors for health damage in terms of long-term exposure. The employer's obligation to assess risks follows from the framework Directive 89/391/EEC [21] and its implementing Directive 2003/10/EC [6]. Possible risk assessment tools are described in ISO standard 14121-2 [28]. The current methods of measuring sound at the limit of audibility may not reflect its real impact on human health. However, research is ongoing in this area, and methods of noise measurement are being developed. Globally (USA, Germany, Great Britain, France, Poland), the trend of complex measurement of specific noise is gaining ground. These measurements take into account not only the frequency of the sound, but also its energy or acoustic pressure. When measuring the impact of sound on humans, the legislation recommends using different \"weightings\" in order to take into account the specific characteristics of the human ear. Sound with low frequencies refers to sound at the threshold of audibility (close to infrasound), and EU legislation and technical standards recommend using \"A-weighting\" when measuring its impact on humans. Although this takes into account the detection of sound by the human auditory organ, it does not take into account the energetic effect of sound on this organ, as well as on the human neuropsychiatric and cardiovascular system and sensory-motor functions. Using conventional A-weighting reduces the measured levels of actual acoustic energy acting on a person. Therefore, some countries are already proceeding with caution when using A-weighting. When measuring low-frequency sounds, they prefer, e.g., C-weighing (Germany). Alternatively, measurements made using C-weighting account for the response of the human ear, with smaller weightings at low frequencies compared to the A-weighting \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline  & **WA1** & **WA2** & **WA3** & **WA4** & **WA5** & **WA6** & **WA7** \\ \hline \(L_{Z}\) at 16 Hz [dB] & 43.54 & 48.82 & 47.02 & 51.86 & 61.59 & 47.49 & 37.81 \\ Point rating & 1 & 2 & 1 & 2 & 2 & 1 & 1 \\ L\({}_{Z}\) at 25 Hz [dB] & 41.70 & 51.65 & 45.58 & 58.95 & 62.76 & 49.16 & 40.19 \\ Point rating & 1 & 2 & 1 & 2 & 2 & 1 & 1 \\ L\({}_{Z}\) at 40 Hz [dB] & 47.68 & 56.97 & 55.63 & 63.45 & 65.96 & 61.54 & 37.65 \\ Point rating & 1 & 2 & 2 & 2 & 2 & 2 & 0 \\ \(L_{Z}\) at 63 Hz [dB] & 56.44 & 56.49 & 55.95 & 62.16 & 63.81 & 58.08 & 49.70 \\ Point rating & 1 & 1 & 1 & 2 & 2 & 2 & 1 \\ \(L_{Z}\) at 80 Hz [dB] & 73.58 & 56.84 & 53.94 & 66.49 & 67.47 & 68.48 & 53.56 \\ Point rating & 2 & 1 & 1 & 2 & 2 & 2 & 1 \\ \(L_{Z}\) at 100 Hz [dB] & 73.20 & 57.24 & 60.02 & 61.67 & 65.49 & 66.85 & 54.32 \\ Point rating & 2 & 1 & 1 & 1 & 2 & 2 & 1 \\ Sum of the point ratings & 8 & 9 & 7 & 11 & 12 & 10 & 5 \\ \hline Degree factor \(Pna\) & 4 (\(M\)) & 4 (\(M\)) & 2 (\(L\)) & 4 (\(M\)) & 4 (\(M\)) & 4 (\(M\)) & 2 (\(L\)) \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Determination of the factor \(Pna\). Source: own research. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Work**} & \multicolumn{4}{c}{**Factors**} & \multirow{2}{*}{**CI**} & \multirow{2}{*}{**Se**} & **Resulting** \\ \cline{2-2} \cline{6-7}  & & & & & & \\ \cline{2-2} \cline{6-7}  & & & & & & \\ \hline WA1 & 1 & 3 & 4 & 1 & 9 & 3 & Medium \\ WA2 & 4 & 3 & 4 & 1 & 12 & 3 & High \\ WA3 & 4 & 3 & 2 & 1 & 10 & 3 & High \\ WA4 & 2 & 3 & 4 & 0 & 9 & 3 & Medium \\ WA5 & 2 & 3 & 4 & 0 & 9 & 3 & Medium \\ WA6 & 2 & 3 & 4 & 0 & 9 & 3 & Medium \\ WA7 & 2 & 1 & 2 & 0 & 5 & 1 & Low \\ \hline \hline \end{tabular}
\end{table} 
Table 8: Calculation of the resulting acoustic risk using the proposed method. Source: own research. filter. This, along with Z-weighting, can be useful to help identify the presence of low-frequency noise.