muffler, in automobiles, device designed to reduce the noise from the exhaust of an internal-combustion engine. When the exhaust gases from an internal-combustion engine are released directly into the atmosphere, they create a loud noise, caused by the passage of the exhaust gases from the high pressure of the cylinder to the normal pressure of the atmosphere. To eliminate or tone down the noise, the gases are led through a pipe to a muffler. Typically a muffler consists of a tubular metal jacket containing perforated pipes and chambers through which the exhaust gases flow before entering the atmosphere. The pipes and chambers are arranged so that the noise from the exhaust gases is reflected back toward the engine or back and forth among the chambers, reducing greatly the amount of noise that is radiated into the environment.