  According to recent theoretical developments, it might be possible to produce
mini black holes in the high energy experiments in the LHC at CERN. We propose
here a model based on the $n$-dimensional Vaidya metric in double null
coordinates for these decaying black holes. The associated quasinormal modes
are considered. It is shown that only in the very last instants of the
evaporation process the stationary regime for the quasinormal modes is broken,
implying specific power spectra for the perturbations around these mini
black-holes. From scattered fields one could recover, in principle, the black
hole parameters as well as the number of extra dimensions. The still mysterious
final fate of such objects should not alter significantly our main conclusions.
