  We compute numerically the quasinormal modes of Kerr-Newman black holes in
the scalar case, for which the perturbation equations are separable. Then we
study different approximations to decouple electromagnetic and gravitational
perturbations of the Kerr-Newman metric, computing the corresponding
quasinormal modes. Our results suggest that the Teukolsky-like equation derived
by Dudley and Finley gives a good approximation to the dynamics of a rotating
charged black hole for Q<M/2. Though insufficient to deal with Kerr-Newman
based models of elementary particles, the Dudley-Finley equation should be
adequate for astrophysical applications.
