Roaring exhaust noises of airplane and war-tank engines can be muffled to a point where they are extremely difficult to detect through sound, by using a suction silencer recently developed, according to Master Sergeant Frank Newlon, an ordnance expert at Fort Rosecrans, He stated that other objects of the silencer are to purify the exhaust gases, thus rendering them harmless, and to reduce the back pressure in the engine’s exhaust system.