A resonator (100) for generating vibratory energy is arranged in line contact with a charge-retentive member (10) bearing an image on a surface thereof, in an electrophotographic device, to apply vibratory energy uniformly to the charge-retentive member. The resonator comprises a suction device ( 162), a suction hron ( 158), and an air-tight seal arrangement. When the vibratory energy is to be applied to the charge-retentive surface, suction is applied at the line of contact of the horn with the surface, to draw the surface into intimate engagement with the horn. The invention has application to a transfer station, for enhancing electrostatic transfer of toner from the charge-retentive surface to a copy sheet, and to a cleaning station, where mechanical vibration of the surface will improve the release of residual toner remaining after transfer.