How can the cochlear amplifier be realized by the outer hair cells which have nothing to push against?

A theoretical consideration is given on how the constituent cells of the cochlear partition can amplify its motion and increase its momentum without resorting to external forces, and it leads to a micromechanical model that explains the role of the cells in the active amplification. The triangle composed of the outer hair cell, the phalanx of Deiters cell and the reticular lamina forms a mechanical unit that stores up and releases strain. When outer hair cells contract in a region along the cochlear partition, strain accumulates in the triangle causing deformation of the region that pushes down the basilar membrane, and hence it appears as a transverse pressure that drives the basilar membrane. The momentum of the region increases at the cost of the momentum of neighboring regions, and the total momentum of the cochlear partition is not altered by the internal forces generated by the outer hair cells. The model can produce a frequency-response curve that compares favorably with experimental data.