a compendium of tech stuff

Jul 31, 2009

On 8:26 PM by Lalith Varun   2 comments

A muffler is a device for reducing the amount of noise emitted by a machine. If you've ever heard a car engine running without a muffler, you know what a huge difference a muffler can make to the noise level. 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. Inside a muffler, you'll find a deceptively simple set of tubes with some holes in them. These tubes and chambers are actuall­y as finely tuned as a musical instrument. They are designed to reflect the sound waves produced by the engine in such a way that they partially cancel themselves out.Take a look at the inside of the above muffler:

The exhaust gases and the sound waves enter through the center tube. They bounce off the back wall of the muffler and are reflected through a hole into the main body of the muffler. They pass through a set of holes into another chamber, where they turn and go out the last pipe and leave the muffler.

A chamber called a resonator is connected to the first chamber by a hole. The resonator contains a specific volume of air and has a specific length that is calculated to produce a wave that cancels out a certain frequency of sound. When a wave hits the hole, part of it continues into the chamber and part of it is reflected. The wave travels through the chamber, hits the back wall of the muffler and bounces back out of the hole. The length of this chamber is calculated so that this wave leaves the resonator chamber just after the next wave reflects off the outside of the chamber.

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. Thus the usage of mufflers in the exhaust system of engines is advisable which has so many merits.


  1. Wow!nice article and containing allot of information about the muffler well done.

    outside of car sound

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