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Experimental study of effectiveness of ear protection devices for prevention of intense noise exposure

Occupational neurosensory deafness is one of central problems in the occupational medicine. Hearing loss associated with professional activity is the leading occupational disease with the permanently increasing share. In the industries with a very high level of noise it is recommended to use a combination of earplugs and earmuffs, and to control the condition of the ear analyzer, which provided a 3-fold increase in regular use of anti-noise earplugs. 
Aim. To evaluates effectiveness of sound damping capacity of ear protectors and of their combinations on exposure to intermittent and impulse noise. 
Materials and Methods. Several types of ear protectors of domestic and foreign manufacture were studied: earplugs of Berushi (Russia) and EAR (Great Britain) types, ShZO-1 earmuffs (Russia) and also earmuffs in conjunction with KKA helmet (Russia). The study was conducted in compliance with the rules and regulations of the effective standards and methodical instructions in the conditions of laboratory experiments and of real production. In the experiment, noise exposure was modeled in anechoic acoustic chamber, after which audiometric research was conducted on test subjects. In real industrial conditions, dimension of levels and noise exposure at the workplaces and the condition of the auditory analyzer of workers were controlled. For subjective evaluation of the design and comfort of the used ear protecting devices and their combinations, questionnaire-based survey was conducted. 
Results. The results of the laboratory experiment and research work in the conditions of the real production permit to suggest high effectiveness of the evaluated ear protectors and of their combinations, and, taking into the account the criterion of preservation of hearing, the quality of hearing protection can be characterized as «good». Questionnaire survey of test persons showed a high sound damping capacity and convenience of the tested ear protectors and permitted to compile the data bank of comments and proposals concerning convenience of their use and their design. 
Conclusions. Laboratory and industrial studies showed a high effectiveness of the tested ear protectors and the possibility of their practical use in the conditions of real production with exposure to extreme levels of intense impulse noise, with the obligatory permanent monitoring of correctness and timeliness of their application.