A sonic damper or sonic dissipator was a device that could lessen or cancel out loud sounds. The Mon Calamari Star Cruiser Remember Alderaan's starfighter hangar bays were equipped with phased-array sonic dampers which muted out the loud roars of starfighters.
Sonic dissipators were small silvery ovoids that attached automatically to surfaces with extruded gripfeet. The bounty hunter Boba Fett used one around 1 ABY to cancel out the noise of an explosion (a noise so loud it almost overloaded the dissipator), in order to retrieve the accountant Nil Posondum from a popular casino.
They were used to cancel the power of the Cacophanizer shell.