## 1 Introduction  
At the worldwide level, there is a large number of studies on health impacts due to occupational and environmental exposure to noise. However, there are still few studies focusing exclusively on health impacts and discomfort due to low-frequency noise (Figure 1). One of the main reasons for this is the low sensitivity of the human auditory system to low frequencies. On the other hand, this type of noise has very particular characteristics and causes much more discomfort and long-term, non-auditory effects [1; 2; 3]. In the 1920s, research on the subject focused on occupational exposure and generally reported physiological changes such as pain in the hands, swelling, and increased vascular tone [4; 5; 6]. Until the 1930s, it was believed that the effects of noise on health were restricted only to hearing loss. In a study published in the Journal of the Acoustical Society of America, [PERSON] et al. [7] concluded that the effects of noise on human health went beyond hearing loss. After the low contribution to the improvement of this scientific field in the 1960s, the 1970s were marked by the emergence of a series of studies addressing annoyance caused by environmental noise [1]. Consequently, during the 1970s and 1980s, studies started focusing on the impacts due to exposure to environmental noise [8; 9]. The 1990s were marked by research aimed at more specific impacts on human health and reported discomfort due to noise [9; 10; 11]. Furthermore, these studies correlated exposure to noise with the onset of cardiovascular diseases [12; 13]. In the 1990s, the World Health Organization (WHO) published documents on the subject, such as the Guidelines for Community Noise, in 1999. Regarding the studies published during the 2000s,the most important are those directed at specific environments, such as schools and residential areas [14; 15]. These studies used a comparison of the noise level measured by using reference curves with the aim of assessing noise discomfort and reinforced the fact that the A-weighting filter is not ideal to evaluate the non-auditory effects of low-frequency noise (LFN) [1; 2; 3]. From 2005, the studies that stand out are oriented to the impacts of low-frequency noise on the quality of sleep [16; 17; 18]. In general, these studies were carried out with voluminous samples involving patient reports, the application of questionnaires, the adoption of cross-sectional studies based on databases, and the comparison of environmental noise levels measured using criteria curves. In fact, these studies reinforced the fact that low-frequency noise is a powerful stressor. The most cited effects on human health refer to emotional changes such as annoyance [19; 20], agitation, and distraction [21; 22; 2], in addition to the association of low-frequency noise with cognitive alterations [23], the development of cardiovascular diseases [24; 25], sleep disorders [26], and high blood pressure [27], and, more recently, the effects of industrial low-frequency noise on dental wear [28; 29]. In the field of occupational medicine, there is a large number of studies that claim that low-frequency noise is an agent that interferes with the performance of work tasks [22; 30]. In addition to these changes, noise can be an agent that affects mental and physical health. In this sense, the effects of noise pollution comprise \"auditory effects\", which directly affect the human auditory system, and \"non-auditory effects\", i.e., the impact of noise on physiological functions. As regards \"non-hearing effects\", discomfort has been reported as the most frequent effect caused by exposure to low-frequency noise in humans [1; 31; 32]. In addition, the discomfort may vary from individual to individual and depends not only on the recorded noise pressure levels but also on the exposure time as well as the low-frequency components present in the measured sound levels. Thus, noise that contains low-frequency components tends to be more annoying than noise without them [1; 33; 34; 35].