Inner ear boundary motion during bone conduction stimulation — Indications for inner ear compression and fluid inertia

A finite element model of a whole human head was developed to study sound transmission by bone conducted sound. The model comprises tissues as bone, brain and soft tissues. With this model, the motion of the bone surrounding the inner ear was investigated. This was done by defining an imaginary box encapsulating the inner ear and analyzing the motion of the opposing sides. According to this analysis, the motion over the surface area was smooth and regular. However, when comparing the motions at the opposing sides the magnitudes differed significantly. This cannot be explained by regular damping of the wave transmission but originates in the complex wave motion in the bone. It also implies that inner ear compression is probably more important for bone conduction hearing than predicted with models using a constant magnitude of the vibration in the bone around the inner ear.