The opportunities and challenges of in-ear noise dosimetry

Résumé

Despite many efforts to reduce sound at the source, noise at work remains a major problem in many industries. While personal hearing protection devices (HPDs) are currently the most commonly used defense against noise induced hearing loss (NIHL), their effectiveness is particularly contingent upon two variables: the ambient noise level and the attenuation of the HPD. Yet in most cases, those two metrics are not precisely known, which leads workers to be inadequately protected. To overcome this problem, recent studies have involved the development of in-ear dosimetric HPDs that are meant to monitor the protected noise exposure levels in real-time. These can offer clear benefits for hearing conservation as they should finally permit to determine whether a given worker is properly protected against noise and, thus, help increasing the effectiveness of HPDs. But to achieve such result, additional research is needed to make the noise levels measured in the occluded ear canal truly representative of the noise dose effectively received by the worker. This research should deal with the acoustical corrections due to the Transfer Function of the Open Ear as well as the resonance between the hearing protector and the subject’s eardrum. It should also address the issues regarding the noise induced by the wearer himself and a potential change in noise susceptibility provoked by the occlusion of the ear canal. Future results should offer additional insight on the use of in-ear noise dosimetry to prevent NIHL.