  An approximate method for studying activation over a fluctuating barrier of
potential is proposed. It involves considering separately the slow and fast
components of barrier fluctuations, and it applies for any value of their
correlation time $\tau$. It gives exact results for the limiting values $\tau
\to 0$ and $\tau \to \infty$, and the agreement with numerics in between is
also excellent, both for dichotomic and Gaussian barrier perturbations.
