A silencer device for a firearm, in particular for a rifle or another long or short firearm, comprising: at least two closing flaps mounted transverse to the axis on the barrel of the firearm in order to temporarily seal the barrel after 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, and 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 to form a gas intake (1, 3) that moves a control mechanism; the control mechanism including at least two amplitude lever arms (8, 12) mounted pivotably on pivots attached to the barrel, each amplitude lever arm (8, 12) being coupled to either one of the closing flaps, the actuation unit (2, 4, 5) engaging with the control mechanism to allow a transverse movement of the closing flaps between an open position, in which the flaps allow ammunition to pass towards the mouth of the barrel, and a closed position, which prevents the passage of the combustion gases and the sound wave after the ammunition has passed, characterised in that the device further comprises: an exhaust unit (11, 21-27) including at least one exhaust pipe (11, 21) disposed on the barrel upstream from the closing flaps so as to redirect the combustion gases and the sound wave and allow them to be discharged from the barrel, and in that the actuation unit (2, 4, 5) includes an actuation piston that disposed in a cylinder attached to the barrel and is extended by a rod, the gas intake made in the barrel moving the piston, extended by the rod, in a direction generally parallel to the axis of the barrel. at least two closing flaps mounted transverse to the axis on the barrel of the firearm in order to temporarily seal the barrel after 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, and 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 to form a gas intake (1, 3) that moves a control mechanism; the control mechanism including at least two amplitude lever arms (8, 12) mounted pivotably on pivots attached to the barrel, each amplitude lever arm (8, 12) being coupled to either one of the closing flaps, the actuation unit (2, 4, 5) engaging with the control mechanism to allow a transverse movement of the closing flaps between an open position, in which the flaps allow ammunition to pass towards the mouth of the barrel, and a closed position, which prevents the passage of the combustion gases and the sound wave after the ammunition has passed, characterised in that the device further comprises: an exhaust unit (11, 21-27) including at least one exhaust pipe (11, 21) disposed on the barrel upstream from the closing flaps so as to redirect the combustion gases and the sound wave and allow them to be discharged from the barrel, and in that the actuation unit (2, 4, 5) includes an actuation piston that disposed in a cylinder attached to the barrel and is extended by a rod, the gas intake made in the barrel moving the piston, extended by the rod, in a direction generally parallel to the axis of the barrel. an exhaust unit (11, 21-27) including at least one exhaust pipe (11, 21) disposed on the barrel upstream from the closing flaps so as to redirect the combustion gases and the sound wave and allow them to be discharged from the barrel, and in that the actuation unit (2, 4, 5) includes an actuation piston that disposed in a cylinder attached to the barrel and is extended by a rod, the gas intake made in the barrel moving the piston, extended by the rod, in a direction generally parallel to the axis of the barrel.