Steady state pressure distribution in a simple model of the cochlea with a rigid basilar membrane

Abstract

Sound propagating through the scalae of the cochlea causes pressure changes which set the basilar membrane in motion. These pressure changes are studied in the present work with a simple model consisting of a tube with a varying diameter and a rigid wall. Analytical expressions are derived for the pressure changes in relation to the geometry of the tube, fluid friction, the acceleration of the liquid in the tube (perilymph) and stiffness of the membrane of the round window. Using a realistic parameter set, the pressure changes turn out to be dominated by the acceleration of the perilymph. The pressure changes are in phase with the acoustic stimulation and their amplitude depends on the geometry of the tube; tapering towards the middle (the helicotreme) turns out to be advantageous; the amplitudes of the differential pressure and the pressure change over the basilar membrane are maximized along the cochlear duct.