AN ARTIFICIAL EAR TO ASSESS OBJECTIVE INDICATORS RELATED TO THE ACOUSTICAL COMFORT DIMENSION OF EARPLUGS: VALIDATION OF A VIBRO ACOUSTIC MODEL FOR INSERTION LOSS AND OCCLUSION EFFECT ASSESSMENT

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 is necessary to use objective indicators correlated to subjective attributes of HPD comfort to help manufacturers designing efficient protectors. For earplugs, the insertion loss (IL), attenuation and occlusion effect (OE) seem 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 complex earcanal geometry. As part of an ongoing project aiming at developing augmented artificial heads for measuring indicators of the acoustical comfort induced by earplugs, the goal of this study is to find parameters of the ear that significantly affect its vibro-acoustical behavior and evaluate a 3D vibro-acoustic finite element model of an artificial ear presented in a companion paper. The artificial ear is placed in anechoic conditions and excited both acoustically and mechanically. Sound pressure is measured at the eardrum location when the earcanal is open or occluded with a specially designed steel earplug and measurement are compared with numerical simulations. This study provides solid bases to the elaboration of augmented artificial ears for earplug comfort assessment.