  A mathematical model describing the coupling between two independent
amplification mechanisms in auditory hair cells is proposed and analyzed. Hair
cells are cells in the inner ear responsible for translating sound-induced
mechanical stimuli into an electrical signal that can then be recorded by the
auditory nerve. In nonmammals, two separate mechanisms have been postulated to
contribute to the amplification and tuning properties of the hair cells. Models
of each of these mechanisms have been shown to be poised near a Hopf
bifurcation. Through a weakly nonlinear analysis that assumes weak periodic
forcing, weak damping, and weak coupling, the physiologically-based models of
the two mechanisms are reduced to a system of two coupled amplitude equations
describing the resonant response. The predictions that follow from an analysis
of the reduced equations, as well as performance benefits due to the coupling
of the two mechanisms, are discussed and compared with published experimental
auditory nerve data.
