Muffler
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- This article is about the engine piece. For the piece of clothing, see Scarf. For a muffler/silencer as fitted to a gun, see Suppressor.
A muffler (North America and Australia) or silencer (outside North America) is a device for reducing the amount of noise emitted by a machine such as an internal combustion engine or a gun. The first was invented by Hiram Percy Maxim to silence firearms. When used on internal combustion engines, the engine exhaust blows out through the muffler.
[edit] Description
Mufflers are typically installed along the exhaust pipe of the engine. They usually contain a series of baffles to absorb sound, although the majority of the noise reduction is not through absorption but through destructive interference in the muffler itself. The muffler accomplishes this with a resonating chamber, which is specifically designed such that opposite sound waves are likely to collide, canceling each other out. They are a common piece of equipment on automobiles, usually slung under the rear of a car, but many diesel-powered semi trucks have large mufflers mounted vertically behind the cab.
Catalytic converters also often have a muffling effect.
[edit] Advantages & Disadvantages
While the goal is to absorb energy that would otherwise be released as sound into the environment, mufflers do force engines to work somewhat harder pushing exhaust gas through them. Therefore, it is a common engine tuning practice to replace stock mufflers with versions that require less energy to force the gas through (usually described as lowering the "backpressure"). Such accessory mufflers can often increase a vehicle's power and fuel efficiency, but usually at the cost of less effective noise suppression.
Some mufflers invented in the later part of the 20th century reduce the engines workload, effectively reducing the "backpressure". This reduction increases the engines efficiency, simultaneously increasing performance, power output, and decreasing the overall wear and tear on the engines' components. As well the sound control is also contained to acceptable levels of the law.
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