  We compute the quasinormal frequencies corresponding to the scalar sector of
gravitational perturbations in the four-dimensional AdS-Schwarzschild black
hole by using the master field formalism of hep-th/0305147. We argue that the
non-deformation of the boundary metric favors a Robin boundary condition on the
master field over the usual Dirichlet boundary condition mostly used in the
literature. Using this Robin boundary condition we find a family of low-lying
modes, whose frequencies match closely with predictions from linearized
hydrodynamics on the boundary. In addition to the low-lying modes, we also see
the usual sequence of modes with frequencies almost following an arithmetic
progression.
