Muffler

Muffler

Muffler installed in a car (view from rear of muffler)

Original equipment mufflers typically reduces the noise level from the tailpipe by bouncing sound waves off of the back, front, and sides of the muffler.[14] They are designed to meet the maximum allowable noise level required by government regulations, however, some original equipment mufflers are a significant source of backpressure.[citation needed]

Glasspack mufflers (also called 'cannons' or 'hotdogs') are straight-through design mufflers that consist of an inner perforated tube, an outer solid tube, and fibreglass sound insulation between the two tubes. They often have less back pressure than original equipment mufflers, but are relatively ineffective at reducing sound levels. Another common type of muffler is the chambered muffler, which consists of a series of concentric or eccentric pipes inside the expansion chamber cavity. These pipes allow sound to travel into them and cause the sound waves to bounce off the closed, flat, ends of the pipe. These reflections partially cancel each other out, reducing the sound level.

Resonators are sections of pipe that expand to a larger diameter and allow the sound waves to reflect off the walls and cancel out, therefore reducing the noise level. Resonators can be used inside mufflers, or also as separate components in an exhaust system.