If your car's muffler is so loud it's waking the neighbours and scaring small dogs, consider installing a muffler silencer. Most auto repair stores and shops carry muffler silencers to fit many makes and models. Or you can save money by making one on your own.
Drill a hole into the top of your muffler near the end. The hole should only be big enough to slip a nail into. The size of your nail will determine the size drill bit to use.
Stuff some steel wool into the end of your muffler. The more steel wool you use, the quieter your muffler will sound. Make sure to completely plug the muffler, because any space around the steel wool will let exhaust and noise escape. All exhaust should have to go through the steel wool.
Slip a nail through the hole in the top of the muffler. The nail should fit snugly. Push the nail through the steel wool, being careful not to crush the steel wool. You want the nail to keep the steel wool in place and keep it from flying out of your muffler.
This silencer won't make your exhaust completely silent, but it will definitely make it a lot quieter.