We belive that Active Galactic Nucleis(AGNs) have one or a few black holes in the center and get the activity from the binding energy of the matter falling into the black hole or(and) the rotational energy of the black hole. Since the sources of their energy exist near the black hole, the energy have to be carried from the vincity of black hole to a distance by some ways. As one of the way, we study the propagation of the waves (ex. The case of the light waves, Hanni 1977, and of sound wave, Takahashi et al. 1990). We investigated the propagation of fast magnetoacoustic wave. We belive the collimation of jet are caused by magnetic field. Further more, we think that the waves can extract the rotational energy of the black hole. This process is the version of wave of Penrose process(Penrose 1968), and is called the super radiant scattering.