  In a previous work we apply lattice point theorems on hyperbolic spaces
obtaining asymptotic formulas for the number of integral representations of
negative integers by quadratic and hermitian forms of signature (n,1) lying in
Euclidean balls of increasing radius. This formula involves an error term that
depends on the first nonzero eigenvalue of the Laplace-Beltrami operator on the
corresponding congruence hyperbolic manifolds. The aim of this paper is to
compare the error term obtained by experimental computations, with the error
term mentioned above, for several choices of quadratic and hermitian forms.
  Our numerical results give evidences of the existence of exceptional
eigenvalues for some arithmetic subgroups of SU(3,1), SU(4,1) and SU(5,1), thus
they contradicts the generalized Selberg (and Ramanujan) conjecture in these
cases. Furthermore, for several arithmetic subgroups of SO(4,1), SO(6,1),
SO(8,1) and SU(2,1), there are evidences of a lower bound on the first nonzero
eigenvalue better than the already known lower bound for congruences subgroups.
