Automotive Q & A

Answer:

Mufflers are part of your vehicle’s exhaust system and are located at the rear, bottom of your vehicle. They aid in dampening vehicle emissions and engine noise. They are made of steel and are coated with aluminum to provide protection from the heat and chemicals released from the exhaust system.

Mufflers are used mainly to dissipate the loud sounds created by the engine’s pistons and valves. Every time your exhaust valve opens, a large burst of the burnt gases used during your engine’s combustion is released into the exhaust system. This release of gases creates very powerful sound waves.

Through the muffler system, sound can actually be cancelled out. If you can introduce a pressure wave that is the exact opposite of the initial sound wave, meaning their wavelengths, or high- and low-pressure points, are opposite, they cancel each other out, and there is no sound. Another way to describe what happens is when one sound wave is at its maximum pressure, the other sound wave is at its minimum pressure; so, they cancel each other out. This is called destructive interference and it’s what occurs inside your muffler.

A muffler design is very simple yet very precise. Inside a muffler there are tubes with perforations that direct the sound waves through the inside of the muffler and out the end. Sound waves will enter through a central tube, hit the back wall, pass through a hole and enter the center chamber. Then the sound wave will travel through another hole and enter the resonator chamber, which is back towards the front of the muffler where the sound waves first entered. Now, some of the sound wave will reflect off the center chamber’s wall, while the rest will pass through the hole and into the resonator chamber.

The resonator chamber has a very specific length in order to produce sound waves that will cancel out other waves. The high-pressure sound wave that traveled through the resonator will join with the low-pressure sound wave that was reflected off the center chamber’s wall and they will cancel each other out. Every aspect of the muffler is designed to aid in cancelling out noise. Even the walls of a muffler are specifically designed; they are actually able to absorb some of the pressure waves and help to cancel out the sound.