PRINCIPLES OF REDUCING THE LEVELS OF LOW-FREQUENCY SOUND AND INFRASOUND IN PRODUCTION AND DOMESTIC CONDITIONS

Abstract

Traditional sound-absorbing materials have been shown to be ineffective in reducing low-frequency sound and infrasound levels. The normalization of these factors requires the development of special protective structures. Therefore, it is appropriate to study the possibility of developing both specific means of protecting workers and the population from th e impact of low-frequency sound and infrasound in specific conditions, as well as the formation of general principles for ensuring the normative values of these factors. Requirements for protective structures have been developed. The main ones are: the use of soundproofing structures should not change the basic operating parameters of devices or technological processes; parameters of soundproofing structures must provide a sufficient level of protection for people; manufacturing technologies of protective structures must be economically acceptable. A calculation device for determining the acoustic load on the environment is provided. Features are shown and calculations are provided for determining the load on the medium of low-frequency sound and infrasound. Functions are provided for calculating the parameters of protective panels of the resonance type for reducing the levels of low-frequency sound and infrasound. The disadvantage of such structures is the adjustment to one resonant frequency. At the same time, it is emphasized that all the given ratios are empirical. Therefore, the real indicators of the resonant frequency under the selected design parameters may differ significantly. This requires ensuring a certain bandwidth of the protective structure. To ensure acceptable protection in the area of low and infrasound frequencies, a two-layer panel is advisable. The second panel is tuned to a resonance frequency different from the first. These frequencies are selected based on the results of field measurements and should have the largest amplitudes in the specified frequency range. The inner panel is made perforated. This reduces the Q-factor of the oscillating system and makes the panel more broadband. It is advisable to fill the space between the panels with noise-absorbing materials, for example, granulated polystyrene. This provides a reduction in the noise level in the entire sound range. Certain disadvantages of the proposed designs are the need to design for specific conditions – room dimensions, wall area, etc.