A muffler or a silencer is a device for reducing the amount of noise emitted by internal combustion engines. It is most commonly seen on the exhaust on most automobiles and motercycles.
Mufflers are typically installed along the exhaust pipe as part of the exhaust system of an internal combustion engine to reduce its exhaust noise. The muffler accomplishes this with a resonating chamber, which is specifically tuned to cause destructive interference, where opposite sound waves cancel each other out. Catalytic converters also often have a muffling effect. The effect is mainly generated largely by restriction, rather than by cancellation.