Acoustical corrections to be used for improved in-ear noise dosimetry measurements

Abstract

Although much effort has been made to reduce sound at the source, hearing protection devices (HPDs) remain currently the most widely used solution against occupational noise exposure in an attempt to prevent noise-induced hearing loss. Such devices, though, often suffer from uncertainties when it comes to ensuring ideal protection for a given individual. These uncertainties stem mainly from three unknown variables: i) the actual attenuation provided by the HPD to the individual; ii) the ambient noise levels; iii) the wear time of the given HPD. In-ear dosimetry (IED) could overcome these issues, as it makes it possible to establish precise personal noise exposures through real-time in-ear noise monitoring. Furthermore, IEDs can be worn in the open, occluded (under earplugs), or cushioned (under earmuffs) ear. Nevertheless, current IEDs are weakened by two inaccuracies: the non-discrimination of self-induced noise, and the lack of acoustical corrections to convert the measured in-ear sound pressure levels to the eardrum and to the free-field. The latter issue is treated in this presentation, which describes methods to identify the appropriate acoustical corrections to be used for improved IED. Such methods aim at personal calibration procedures, so that the unique ear geometry of each individual is accounted for. Preliminary results will be presented as a comparison between theoretical and experimentally measured corrections on human test-subjects.