Abstract: The invention relates to a silencer device for a firearm, in particular for a rifle or another long or short firearm and a silencing method, which comprises: at least two closing flaps (10) mounted across the axis on the barrel of the firearm in order to provisionally seal the barrel after the ammunition has passed and to prevent the passage of the combustion gases and the sound wave towards the mouth of the barrel when a shot is fired, an actuation unit (2, 4, 5) including at least one opening (1, 3) made in the barrel of the firearm upstream from the closing flaps (10) to form a gas intake (1, 3) moving a control mechanism (6-9); the control mechanism (6-9) including at least two arms of an amplitude lever (8, 12) pivotably mounted on pivots (7) attached to the barrel, each arm of the amplitude lever (8, 12) being coupled to either one of the closing flaps (10), the actuating unit (2, 4, 5) engaging with the control mechanism (6-9) to allow a transverse movement of the closing flaps (10) between an open pos