  Mechanism of two-tone suppression is studied using a coupled-oscillator model
of the cochlea with feed-forward coupling. Local amplification of sound signals
is modeled by using Stuart-Landau oscillators near the Hopf bifurcation, and
transmission of sound signals is described as feed-forward coupling between the
oscillators. Effect of suppressor signals on the response to probe signals is
analyzed by numerical simulations. It is found that the effect of suppression
is qualitatively different depending on relative frequency between probe and
suppressor signals. By analyzing a simplified two-oscillator model, we explain
the mechanism of the suppression, where configuration of the oscillators plays
an essential role.
