**1. Introduction**

In accordance with modern concepts, noise and infrasound are classified as harmful and dangerous physical factors, the impact of which causes a decrease in efficiency and reliability of activity, and a long or short cumulative effect causes the development of a number of diseases [1–3].

To date, a large amount of data has been accumulated on the adverse effects of noise on humans. The nature of this influence depends on the sound level, the duration of exposure and the spectral composition of the noise [4–6]. The hearing organ is the critical organ of the body when exposed to noise. It is generally accepted that the most harmful effect on the organ of hearing is provided by noise, the spectrum of which is dominated by high frequencies of the sound range (from 1 to 8 kHz). In the clinical picture, along with hearing impairment, pathology of the cardiovascular and nervous systems is often found, which made it possible to form the concept of "noise disease" [7].

The physical characteristics of infrasound are well studied by acousticians, however, hygienists and occupational pathologists have long been limited in their research by the lack of reliable and affordable measuring equipment. Therefore, the history of the study of infrasound as a factor in the environment and production environment is relatively short. The first publications devoted to the action of infrasound appeared in the period 1970–1980. During this period, reports appeared in the scientific literature about the high biological efficiency of infrasound [1, 7, 8]. The first hygienic standards for infrasound in the USSR were adopted only in 1981, while the first noise standards for its limitation in workplaces were adopted in 1956. Subsequently, a large number of publications appeared, which reflect the point of view of hygienists on the problem of infrasound effects on humans [1, 7].

Since 2004, infrasound has been included in the list of harmful and hazardous production factors in Russia. The critical organs under the influence of infrasound include not only the organ of hearing, but also the vestibular analyzer, the central and autonomic nervous system, the circulatory and respiratory organs [9–12]. The presence of several organs and systems in the clinical picture allows us to speak about the separation of infrasound pathology into a separate nosological form [1].

There are reports that low-frequency noise can have a harmful effect not only on the organ of hearing, but also on other human organs and systems. Its biological effect has a certain similarity with the effect of infrasound on the human body. An analysis of industrial and transport noise shows that its spectrum is dominated by low frequencies of the audible and infrasound ranges. Close physical parameters and biological effects allowed a number of authors to introduce the terms "low-frequency acoustic oscillations", "infrasonic disease" and "vibroacoustic disease" [1, 7].
