Speaker
Description
The occlusion effect (OE) induced by intra-aural devices is a major source of acoustic discomfort, often limiting the proper use of earplugs and hearing aids. This phenomenon originates from the amplification of body‑conducted sounds, particularly at low frequencies, caused by the increased acoustic pressure radiated by the vibrating earcanal wall and intra-aural device when the ear is occluded. Understanding earcanal wall vibration is therefore essential to mitigate the OE at its source. Yet, direct measurements on the earcanal wall remain challenging due to its small size and complex anatomy. Analytical models represent the acoustic effect of earcanal wall vibration using a flow source positioned at the centroid of the wall’s normal velocity distribution. An indirect acoustic method employing resonators coupled to the ear has been previously proposed by the authors to estimate this centroid position experimentally. The present study investigates the relevance of this centroid as an acoustic indicator of a point of predominant vibration contributing to the OE. A vibroacoustic finite element model of a simplified outer ear is used to analyze the relationship between wall vibration distribution and centroid position. The acoustic estimation method is then applied to the virtual ear to assess its feasibility and optimize its precision prior to human testing. Finally, series of length‑controlled custom occlusion devices are evaluated numerically to examine the sensitivity of the OE to device-skin coupling with respect to this indicator. Results demonstrate the potential of this approach to inform design strategies aimed at reducing tissue‑conducted sound and mitigating the OE induced by intra-aural devices.