  The spectra of Sinai microwave billiards and rectangular billiards with
statistically distributed circular scatterers have been taken as a function of
the position of one wall, and of one of the scatterers, respectively. Whereas
in the first case the velocity distribution and correlations obey the universal
behaviour predicted by Simons and Altshuler, in the second case a completely
different behaviour is observed. This is due to the fact that a shift of one
wall changes the wave function globally whereas the displacement of one
scatterer only leads to a local perturbance.
