There are a few things you can do to decrease the amount of sound your bike/ATV is putting out. Lets start with the exhaust, full race exhaust systems put out a lot of sound because they're smaller to save weight therefore they don't have a lot of packing material inside to help absorb the sound waves. If sound is a concern make sure you have the appropriate muffler installed on your machine. We offer many different exhausts that will address your needs.
Make sure your silencer/muffler has been re-packed lately and properly. Packing does go bad and will in turn make your machine louder over time.
Remember, not all the sound comes right out of the exhaust. If you've vented the air box or removed the lid, close it back up.
Also make sure all your nuts and bolts are tight so they don't rattle.
Also when a test is being performed, make sure you've got the transmission in neutral, with the clutch pulled in, this will also keep some of the noise down.