AN ARTIFICIAL EAR TO ASSESS OBJECTIVE INDICATORS RELATED TO THE ACOUSTICAL COMFORT DIMENSION OF EARPLUGS: COMPARISON WITH ATTENUATION AND OCCLUSION EFFECT MEASURED ON SUBJECT

摘要

Hearing protection devices (HPD) are widely used to prevent noise-induced hearing loss (NIHL). In a noisy environment, wearing a correctly fitted HPD during all the time exposure is the sine qua non condition to prevent NIHL. However, this condition is often unfulfilled due to the discomforts induced by HPDs. Although this is a well-known fact, it remains challenging to quantify HPD comfort since it is a multidimensional concept related to subjective feelings of the users. Thus, it seems necessary to use objective indicators correlated to subjective attributes of HPD comfort to help manufacturers to design efficient protectors. Those indicators would also help an adequate HPD selection by users. For earplugs, the insertion loss (IL), attenuation and occlusion effect (OE) are good candidates to objectively describe attributes belonging to the acoustical dimension of comfort. However, most of the current ear simulators are not adapted to evaluate the physical variables related to these indicators since they do not consider important features of the external ear such as the earcanal geometry or the tissues surrounding it. As part of an ongoing project aiming at developing augmented artificial heads for measuring indicators of the acoustical comfort dimension induced by earplugs, this study presents an artificial ear to assess objective indicators related to attributes of the acoustical comfort dimension of earplugs. This testing device has a realistic geometry and includes synthetic tissues mimicking the real human ear's bone, cartilage and soft tissues. Its design and fabrication steps are presented. The ability of the device to assess objective indicators related to comfort attributes of earplugs is investigated by comparing attenuation and occlusion effect measurements performed on the artificial ear, a subject and an acoustic test fixture. Limits of the device such as its material properties, the absence of tympanic membrane and boundary conditions are discussed.