We study the mobility of an overdamped particle in a periodic potential til
ted by a constant force. The mobility exhibits a stochastic resonance in in
homogeneous systems with space dependent friction coefficient. The result i
ndicates that the presence of an oscillating external field is not essentia
l for the observability of stochastic resonance, at least in an inhomogeneo
us medium. (C) 1999 Elsevier Science B.V. All rights reserved.