  A typical problem in the detection of the gravitational waves in the data of
gravitational antennas is the non-stationarity of the Gaussian noise (and so
the varying sensitivity) and the presence of big impulsive disturbances. In
such conditions the estimation of the standard deviation of the Gaussian
process done with a classical estimator applied after a "rough" cleaning of the
big pulses often gives poor results. We propose a method based on a matched
filter applied to an AR histogram of the absolute value of the data
