Geometric Stochastic Resonance
  A Brownian particle moving across a porous membrane subject to an oscillating force exhibits stochastic resonance with properties which strongly depend on the geometry of the confining cavities on the two sides of the membrane. Such a manifestation of stochastic resonance requires neither energetic nor entropic barriers, and can thus be regarded as a purely geometric effect. The magnitude of this effect is sensitive to the geometry of both the cavities and the pores, thus leading to distinctive optimal synchronization conditions. 
Pulak Kumar Ghosh, Fabio Marchesoni, Sergey E. Savel'ev and Franco   Nori
physics.chem-ph cond-mat.soft cond-mat.stat-mech