The occlusion effect (OE) describes the increased perception of body internal sound such as one’s own voice when the ear canal is blocked. This phenomenon often leads to discomfort with hearing aids or hearing protection devices. There are two common approaches for the assessment of the OE. The objective OE which is based on ear canal sound pressure level differences and the subjective OE defined by changes in hearing threshold levels. Discrepancies between these two remain little understood. In this study a numerical head model including the ear canal, middle ear and inner ear structures was used to investigate the vibro-acoustic mechanisms underlying these discrepancies. First, the model was validated against available experimental data from literature which covered different bone conduction pathways. This enabled the simulation of bone conducted excitation under unoccluded and occluded ear canal conditions. For skull stimulation at mastoid position, the simulation results showed good agreement with the experiments, whereas soft tissue stimulation could not be fully validated due to remaining uncertainties. The results suggest that the relative volume velocity of the oval window is a promising predictor of the subjective OE over a broad frequency range. Moreover, at low frequencies, changes in an equivalent impedance of the tympanic membrane and oval window were found. Combined with an outer ear based estimate of the volume velocity at the oval window for bone conduction, derived from the air conduction middle ear transfer function, these results suggest that the outer ear pathway dominates when the ear canal is occluded. Such a clear dominance is not evident in the unoccluded case. Consequently, ear canal sound pressure appears to be a reliable measure for determining the OE only under occluded conditions.

Melden Sie sich hier an um Einladungen zu den Kolloquium-Vorträgen per E-Mail zu erhalten.
Register here to receive the invitations to colloquium talks via e-mail.

Zoom-Meeting-ID: 954 4073 3814
Passwort: 450783