What Is a Suppressor? If your idea of a suppressor comes from the movies, where a gun makes a soft "pfft" and nobody in the next room notices, it's time for a reality check. Real suppressors don't make firearms silent. They make them quieter, often turning a painfully loud blast into something closer to a sharp, muffled bang. A suppressor (also called a silencer or sound moderator, depending on where you live) is a tube-shaped device that attaches to the muzzle of a firearm. Its job is to slow d …