The spectrum of the Mossbauer gamma-radiation, passed through a resonant absorber vibrated at ultrasonic frequencies, is studied in a new approach. An analytical expression is derived for the line profile, which consists of an infinite series of equidistant satellites. Their intensities depend on both the vibration amplitude and the absorber thickness. Certain ideas appearing in the investigations so far are critically discussed. Most of the phenomena considered can be explained by the classical waves dispersion theory.