Mufflers are typically installed along the exhaust pipe as part of the exhaust system of an internal combustion engine (of a vehicle, or stationary) 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.

Mufflers that reduced backpressure relative to earlier models became increasingly available in the late 20th century, and resulted in increased engine efficiency, performance, power output, and simultaneously decreased overall wear and tear on the engines' components, as well as sound to levels in compliance with the law.

A mini-muffler (also known as a "hotdog" in the auto industry) can be put in place of a normal muffler in a car exhaust system to "enhance" the sound of the exhaust for a car enthusiast. These are smaller, cost usually about half the price of a normal muffler and work in a similar way, but allowing more sound through. By using a specific muffler / mini-muffler / catalytic converter combination, the sound of a car's exhaust system can be changed considerably. Any removal of a muffler from a "factory" setup will of course risk the resulting noise being over government approved noise levels and may attract unwanted attention from the law.