| Many workers are exposed to noise levels high enough to put them at risk of losing their hearing. However, noise reduction at the source, when technically feasible, is often difficult to implement for economical reasons. Therefore, individual hearing protection remains the most widespread solution in practice. Unfortunately, the hearing protectors currently available on the market are seldom worn continuously as they should be (because they are not very comfortable or must be removed to communicate) and do not match the worker's need for protection (because their actual attenuation is generally unknown). This doctorate thesis work, carried out in close collaboration with SONOMAX HEARING HEALTHCARE I NC., had the general objective to develop a smart earplug that would solve the problems associated with current hearing protection devices thereby effectively preventing noise induced hearing loss in the industrial environment. The issues associated to this development have been formulated in details under the Health and Safety aspect (non-continuous wearing of the hearing protector and un-adapted protection), technical aspects (development of an earplug that is comfortable both from the physical and sound perception points of view and whose performances are measurable) and scientific aspects (modeling of physical systems, signal processing, instrumentation and measurement techniques). The technical developments have resulted in a custom earplug that is instantly fitted to the wearer's ear by silicone injection. Its acoustical performance can be measured using a microphone probe while the attenuation can be adapted to the user's need by the insertion through the earplug of passive acoustical filters. The scientific developments have resulted in the prediction of the attenuation of the earplug from the Noise Reduction measurement and in the prediction of the filtered earplug attenuation. |
