  The waveforms from binary black hole mergers include inspiral, merger, and
ringdown parts. Usually, the inspiral waveform can be obtained by calibrating
from post-Newtonian approximation; The merger and ringdown ones can be gotten
from the quasinormal modes with black hole perturbation theory. However, for
more general black holes, the calculation of the quasinormal modes is not
trivial. In this paper we use the photon sphere to get the quasinormal modes of
spinning black holes. Then we connect the ringdown wave with the inspiral part
to get full waveforms and compare with the ones from numerical relativity. We
find that they match with each other very well. In principle this method can be
extended to some general compact objects. As an example, the ringdown waveforms
from parametrized axisymmetric black holes are obtained. We also use this
method to get the ringdown signals of the accelerating final black hole; this
is due to gravitational recoil during the merger. Even for the extreme cases,
the acceleration due to the recoil cannot produce detectable effects.
