  Calculations of black hole entropy based on the counting of modes of a
quantum field propagating in a Schwarzschild background need to be regularized
in the vicinity of the horizon. To obtain the Bekenstein-Hawking result the
short distance cut-off needs to be fixed by hand. In this note we give an
argument for obtaining this cut-off in a natural fashion. We do this by
modelling the black hole by its set of quasinormal modes. The horizon then
becomes a extended region: the quantum ergosphere. The interaction of the
quantum ergosphere and the quantum field provides a natural regularization
mechanism. The width of the quantum ergosphere provides the right cut-off for
the entropy calculation. We arrive at a dual picture of black hole entropy. The
entropy of the black hole is given both by the entropy of the quantum field in
the bulk and the dynamical degrees of freedom on the horizon.
