How does a gun silencer work?

Silencers are a necessary part of every secret agent's stock-in-trade-at least as far as the movie-going public is concerned.

Silencers work best on weapons that eject their ammunition at speeds that are slower than that of sound. Otherwise, the supersonic bang would make an additional noise. The remainder of the bang comes from the hot gases created by the exploded gunpowder, which is what drives the bullet from the barrel. The more these gases can be slowed down, the less noise there is.

            Silencers are usually made up of two areas-an expansion chamber and a number of baffles. In the expansion chamber, the hot gas suddenly has more room to move and is able to expand and become cooler and the molecules collide less frequently. This principle is also used for the silencers on motor vehicle exhaust pipes. The baffles in the silencer cause further declaration by causing the hot stream of gas to swirl and -because they are made from metal-they absorb part of its thermal energy.