Hearing protection devices with active attenuation control for quarry employment

Occupational diseases linked to noise risk are still one of the most important employment problems, particularly in the quarry activities. Many negative effects on human health can arise after long exposure to noise in an occupational context. To protect workers' health and prevent hearing problems, employers must provide to workers with hearing protection equipment. In recent years, however, there have been many problems with the use of hearing protection devices. These have a highly mitigating effect but can isolate the user from the outside environment, as transit of a vehicle or movement of a digger. This aspect must be treated with care because the workers cannot hear the sound of a hazard alarm or communication with other people during daily activities, for example in a quarry site. Generally, these types of hearing protection devices are made using an exclusively passive mechanism system, which is the related to the insertion loss. For this reason, an experimental campaign was carried out for the purpose of analyze the characteristics of devices equipped with electronic sound amplification systems. The tests were carried out in a sound laboratory with a special noise source on a human mannequin in order to replicate as much as possible the real noise exposure. The aim of the tests was to analyze the behavior of hearing protectors under different noise levels in order to comprehend the degree of effective protection for workers. The signal analysis was carried out in the third octave band, calculating the different noise levels in the frequency spectrum for the different noise levels of the source. The data obtained show that electronically controlled protection devices allow sound to be heard from the environment but at the same time protect against dangerous high noise levels. The results obtained demonstrate the importance of the performance of these devices compared to those based on insertion loss.