  Low-frequency current fluctuations are investigated over a bias range
covering {\em ohmic}, {\em trap-filling} and {\em space-charge-limited current}
regimes in polycrystalline polyacenes. The relative current noise power
spectral density ${\cal S}(f)$ is constant in the {\em ohmic} region, steeply
increases at the {\em trap-filling transition} region and decreases in the {\em
space-charge-limited-current} region.
  The {\em noise peak} at the {\em trap-filling transition} is accounted for
within a {\em continuum percolation model}. As the quasi-Fermi level crosses
the trap level, intricate insulating paths nucleate within the ohmic matrix,
determining the onset of non-equilibrium conditions at the interface between
the insulating and conducting phase. The {\em noise peak} is written in terms
of the free and trapped charge carrier densities.
