The muffler is one part of the vehicle that is hard to ignore. If there is a problem with this crucial part, you'll likely hear it when you start the car. The muffler's job is to reduce the noise coming from the engine, so if your car is louder than usual, the muffler is a good place to start diagnosing the issue - although it may not always be at fault.
Ultimately, you know your car better than anyone else. After years of driving it, you should be attuned to the noises it makes, even if you're not actively listening. Thus, if it sounds like something is off, it pays to check it out rather than just dismissing it as a figment of your imagination.
If your muffler does have an issue, you'll likely be able to tell just by listening to your exhaust system. However, there's a more accurate way to determine exactly what the problem is.
Park your car, but leave the engine idling. It's best to put on a pair of gloves for this one. Head to the back of the car and put your hand in front of the tailpipe. Normally, this is where the exhaust flow will be expelled, but it can be tough to see. This is why you need to put your hand over the pipe opening, to determine if anything is coming out. If you don't feel a flow of air against your hand, it's possible that your muffler has a leak.
To further diagnose this issue, you'll have to get your hands dirty. Well, you won't technically have to if you're still wearing those gloves, which will also protect against heat. Turn the engine off and jack up the rear of the car, making sure to block off the wheels for safety. Crawl underneath and follow the tailpipe back until you locate the muffler.
If the sounds appear to be coming from the middle or rear of the car, then you should inspect the muffler and pipes leading to it. In general, you should be looking for any black soot that has built up on the pipes or the muffler itself. This could indicate a leak somewhere in the exhaust system. You may be able to visually see a crack in the piping. Make sure to double-check areas such as where the pipes connect to the muffler, using your hands to see if you can feel any gas coming out.
Carbon monoxide is both odorless and invisible, but that doesn't mean it's not harmful. In fact, a report by the EPA found that carbon monoxide could be found at abnormal levels in approximately 20 percent of auto crashes. At low levels, this gas is known to cause dizziness, headaches and nausea - which could be almost as debilitating as driving drunk. At high levels, the gas can kill. So be sure to quickly take your car in for repairs - this isn't something you can safely ignore.
You should also knock on the muffler with your hand to see if you can hear the interior bafflers. These are the parts of the muffler responsible for reducing noise, but sometimes they can deteriorate and stop functioning over time. The bafflers should vibrate against the bottom of the muffler.
If the noises seems to be coming from closer to the front of the car, your muffler's probably fine. However, there still could be an issue with the vehicle, so you may want to take it in for further diagnosis and repairs.