  We present a model for tail wavelets, a phenomenon also known as "echo" in
the literature. The tail wavelet may appear in signal reconnaissances in the
merger of binary compact objects, including black holes and neutron stars. We
show that the dark matter surrounding the compact objects lead to the
speculated tail wavelet following the main gravitational wave (GW). We
demonstrate that the radiation pressure of the main wave is fully capable of
pushing away the the surrounding matter to some altitude, and splashing down of
the matter excites the tail wavelet after ring down of the main wave. We
illustrate this idea in a simplified model, where numerical estimations are
carried out concerning the specific distribution of the dark matter outside the
black hole horizon and the threshold values in accordance with observations. We
study the full back reaction of the surrounding dark matter to the metric, and
find that the effect is insignificant to the tail wavelets. We find the fine
difference between the tail wavelets of a dressed black hole and a bare one. We
demonstrate that the tail wavelet can be a natural phenomenon in frame of
general relativity, without invoking any modified gravities or quantum effects.
