## 1 Introduction  
Risk assessment is one of the basic pillars of the occupational health and safety management system [1]. Low-frequency noise (LFN) is one of the most harmful and annoying factors affecting people in their work and living environment [2]. An international definition of LFN has not yet been formulated, which is why its exact limits are not specified. It is usually defined according to several sources [2; 3; 4; 5] as broadband noise with a dominant sound energy in the frequency band range from 10 Hz to 250 Hz (limits of 100 Hz, 160 Hz, or 200 Hz are also given). In the EU, it is defined according to the relevant legislation [6] as audible sound, the frequency spectrum of which is in the third-octave bands, with mean frequencies of 20 Hz to 40 Hz. Many studies [2; 3; 4; 7; 8; 9] show that low-frequency waves differ from medium-frequency and high-frequency waves by several specifications, including a higher intensity of energy transmission, which is differently propagated and reduced. The specific characteristics of LFN compared to audible noise define that at low frequencies, there is a sharp increase in volume and the absorption is too low; therefore, the distances of propagation are large. This fact is also a problem in the work environment, where the measurement of noise exposure is performed using an A-weighting filter, which does not record the acoustic energy acting on humans. Acoustic energy at low frequencies has higher volume values that are not captured by the A-weighting filter. According to studies [10; 11; 12], a higher degree of discomfort has been reported by workers who are exposed to LFN. The subjective symptoms of LFN were fatigue, dizziness, a feeling of pressure in the head and on the endrum, and mood swings, which affect people in their work performance [13] by reducing their attention and concentration. Speechintelligibility is significantly affected by frequencies as low as 20 Hz. Disruption of the vestibular system results in disorientation, nausea, or imbalance [9]. It can be argued that this type of noise increases work stress, which increases cognitive load and thus increases the likelihood of errors. This increases the likelihood of accidents at work [14]. One of the most common employee complaints is low frequency noise from 20 Hz to 250 Hz [15; 16]. The discomfort that occurs even when the audibility threshold is only slightly exceeded is the dominant effect of low frequencies on the human body during exposure to it in the workplace. LFN can be perceived as a mixture of sound and tactile stimuli, which causes pressure in the ears and feelings of vibration on the body [17]. The low-frequency mechanical vibrations generated by machines and machine systems cause disturbing dynamic forces, most often caused by unbalance, a non-coaxial connection of rotating components, inappropriate clearance of mutually moving components, mechanical loosening, misalignment, incorrect lubrication, technological processes, or insufficient maintenance [18]. The most important sources of LFN include, for example, fluid flow in machinery, industrial activities and technologies, powerful ventilation and air conditioning equipment, and pumps [18; 19; 20], which are also part of the working environment. In the framework of Council Directive 89/391/EEC [21] on occupational health and safety, which sets a requirement for the assessment of hazards in the work process, this paper proposes a method for assessing the impact of noise on workers at work, which includes the incorporation of Directive 2003/10/EC [6] on the minimum health and safety requirements regarding the exposure of workers to the risks arising from physical agents. This method also takes into account the impact of low-frequency values of normalized noise exposure \(L_{Z}\), which pose a hazard. The A-weighting filter underestimates the sound pressure levels of LFN.