Noise assists detection of subthreshold signals — SNR peaks at optimal noise level
—
SNR (dB)
0.50
Noise σ
0.60
Signal A
1.00
Threshold
Stochastic resonance (Benzi 1981, Wiesenfeld-Moss 1995): a double-well or threshold system driven by a subthreshold periodic signal A<Θ. Adding noise of the right amplitude causes the particle to cross the threshold in sync with the signal. SNR is maximized at an optimal intermediate noise level — not zero noise! Bottom panel shows SNR vs noise from a sweep.