A muffler is simply a sound-reducing device attached to the exhaust system on your vehicle. It causes the loud explosions that take place in the engine's combustion chamber to be released with a more tolerable tone. If a muffler is not used, the sound can be annoying or deafening. It's for those reasons that they were invented. It's a part that's simply meant to stifle a natural symptom of an internal combustion engine. Most exhaust parts are made from treated steel because it is more durable than other metals. They are packed with baffles that are designed to bounce the sound waves around the interior so as to reduce the strength of the sound waves that are eventually emitted out of the tail pipe.
Mufflers aren't usually replaced within the warranty life of a car because they are made with such durable material that they'll last a very long time. The overwhelming majority reason to replace one is rust. Over time, the steel will rust, and the exhaust system with develop leaks and soft spots that no longer lessen the sound as much as it should. Oxidation is especially a problem for vehicles closer to moist, salty air, such as the ocean. Both moisture in the air and the salt in the air nearer to the ocean can cause rust by themselves, so when they're both present, rusting can occur much faster. Most mufflers are treated with chemicals to slow the process, but rust is inevitable. If it does need to be replaced, it's usually not a very expensive repair. You can expect to pay a few hundred dollars for the part and about the same amount for the labor to weld it in, or bolt in if it has a flange. When looking for a muffler to use on your vehicle, try to find the same brand that used originally for the vehicle so the sound dampening remains the same as it was when it was new. Car manufacturers have to abide by strict sound regulations which vary depending on your location. There is typically some room under the legal limit is the muffler you purchase is a little louder, but not much. There are some people who replace theirs with louder ones intentionally. If a police car pulls them over, they could receive a ticket and need to have the sound level checked. If the sound is above the legal limit, they'll need to spend the money to change it back out again.
Mufflers are typically either welded right on to the exhaust pipes, or they have flanges to bolt them to the pipes. Because modern cars have more sophisticated rear suspension and exhaust systems, the pipes and mufflers are put in as one piece from the factory, and the rest of the rear end is fitted around them. So, if yours does need to be changed, it will likely include some of the exhaust pipe before and after, as well as mounting flanges for easy installation. A certified exhaust shop should be able to perform the repair for a nominal fee.
If the muffler needs to be replaced, it's a good idea to replace it as soon as possible. Although it probably won't cause any damage to the car, you could be pulled over and ticketed, and you sure won't be making any new friends with the neighbors. Car Parts Discount has a wide selection of mufflers available for different vehicles. We carry the top brands and have the lowest prices.