  In terms of linearized Gross-Pitaevskii equation we have studied the process
of sound emission arises from a supersonic particle motion in a Bose-condensed
gas. By analogy with the method used for description of Vavilov-Cherenkov
phenomenon, we have found a friction work created by the particle generated
condensate polarization. For comparison we have found radiation intensity of
excitations. Both methods gives the same result.
