Mechanism of stochastic resonance

Stochastic resonance in an overdamped oscillator is considered theoretically. It has been shown that a seeming resonance is actually caused by a noise-induced change in the effective stiffness and damping factor with respect to a signal. For a certain noise intensity, the effective stiffness is minimal, which leads to a nonmonotonic variation of the output-signal amplitude as a function of noise intensity. It is substantial that the position of the minimum of the effective stiffness and its value depend strongly on the signal frequency. The results are compared with similar processes for vibrational resonance. Considerable differences between these phenomena are indicated.