  The phenomenon of stochastic resonance (SR) is known to occur mostly in
bistable systems. However, the question of occurrence of SR in periodic
potential systems is not conclusively resolved. Our present numerical work
shows that the periodic potential system indeed exhibits SR in the high
frequency regime, where the linear response theory yields maximum frequency
dependent mobility as a function of noise strength. The existence of two (and
only two) distinct dynamical states of trajectories in this moderately
feebly-damped periodically driven noisy periodic potential system plays an
important role in the occurrence of SR.
