Muffler is a device that greatly reduces the exhaust noise of an engine. Mufflers are used on nearly all automobiles. The exhaust of a gasoline engine originates in the cylinders. When the exhaust leaves the cylinders, it is at a much higher temperature and pressure than the outside air (see Gasoline engine ). If released directly into the air from the cylinders, the exhaust would expand suddenly, producing a loud, sharp noise. In the muffler and in other parts of the exhaust system, the gases are allowed to expand gradually and to cool. The pressure is thereby reduced, and little noise results when the exhaust is released.
