  In this article, we investigate the stochastic resonance (SR) effect in a
finite array of noisy bistable systems with nearest-neighbor coupling driven by
a weak time-periodic driving force. The array is characterized by a collective
variable. By means of numerical simulations, the signal-to-noise ratio (SNR)
and the gain are estimated as functions of the noise and the interaction
coupling strength. A strong enhancement of the SR phenomenon for this
collective variable in comparison with SR in single unit bistable systems is
observed. Gains larger than unity are obtained for some parameter values and
multi- frequency driving forces, indicating that the system is operating in a
non-linear regime albeit the smallness of the driving amplitude. The large SNR
values observed are basically due to the fact that the output fluctuations are
small and short lived, in comparison with their typical values in a linear
regime. A non-monotonic behavior of the SNR with the coupling strength is also
obtained.
