3D finite element modeling of earplug-induced occlusion effect in the human ear.

Poor utilization of earplugs among military personnel may be due to discomfort caused by the occlusion effect (OE). The OE occurs when an earplug occludes the ear canal, thereby changing bone conduction (BC) hearing and amplifying physiological noises from the wearer. There is a need to understand and reduce the OE in the human ear. A 3D finite element model of the human ear including a 3-chambered spiral cochlea was employed to simulate the OE caused by foam and aerogel earplugs. 90 dB sound pressure was applied at the ear canal entrance and BC sound was applied as vibration of the canal bony wall. The model reported the ear canal pressure and the displacements of the stapes footplate and cochlear basilar membrane with and without earplugs. Without BC stimulation, the foam earplug showed a greater pressure attenuation than the aerogel earplug. However, the foam earplug results were more affected by BC stimulation, with a maximum sound pressure increase of 34 dB, compared to the 21.0 dB increase with the aerogel earplug. The aerogel earplug's lower OE demonstrates its promise as an earplug material. Future work with this model will examine BC sound transmission in the cochlea.