Effects of noise on the intensity of distortion product otoacoustic emissions.

Distortion product otoacoustic emission (DPOAE) is a widely used differential diagnostic method for diagnosing inner ear disorders. It provides us information on the condition of the outer hearing cells (OHCs). Otoacoustic emission occurs only when the OHCs are functioning normally. Changes in thresholds of DPOAE curves can provide us important information on the activity of the OHCs. The inner ear shows nonlinear properties if the OHCs are functioning normally. If OHCs are injured and thus function improperly, the system stops showing nonlinear properties. If we have a system with periodic excitation and, with the addition of white noise, the signal-to-noise ratio on the output increases (at least for small noise intensities), we have witnessed what is called phenomenon stochastic resonance. Our goal was to elucidate how white noise influences the intensity of DPOAE. If there is emission, that specific ear surely exhibits nonlinear behavior, which in turn is the basic property needed for stochastic resonance.