  The statistics of transitions between the metastable states of a periodically
driven bistable Brownian oscillator are investigated on the basis of a
two-state description by means of a master equation with time-dependent rates.
The results are compared with extensive numerical simulations of the Langevin
equation for a sinusoidal driving force. Very good agreement is achieved both
for the counting statistics of the number of transitions and the residence time
distribution of the process in either state. The counting statistics
corroborate in a consistent way the interpretation of stochastic resonance as a
synchronisation phenomenon for a properly defined generalized Rice phase.
