On the sound pressure distribution in the inner ear induced by rigid body vibration

Intracochlear sound pressure measurements are essential for understanding inner ear function. During bone conduction (BC) stimulation, these pressures exhibit pronounced variability and similar magnitudes in the two scalae, making their interpretation challenging. These characteristics arise from the vibration of the entire inner ear and interactions between the different BC mechanisms. Using fundamental acoustic principles, we derive characteristics of intracochlear pressure distributions driven by fluid inertial effects from rigid body vibration of the inner ear. Our analysis shows that the vibration at a spatially uniform velocity in a single direction results in (1) proportionality of the pressure to stimulation velocity and frequency, (2) a linear pressure variation along the vibration direction, (3) uniform pressure in planes perpendicular to the motion, and (4) minimum pressure at a plane approximately aligned with the round window centroid. The superposition principle allows the extension of these results to any complex-valued amplitude vector of rigid body translation. The findings provide insights into the variability of experimental intracochlear sound pressure measurements and enhance the understanding of the interactions between the mechanisms involved in BC hearing.