Recently I have constructed a sound suppressor, or silencer. This device is especially useful when you do not want to bother other people (such as pesky neighbors).   The design that I used was very basic, yet effective. The main barrel was ported with many small holes. The holes followed a rifling pattern, very similar to a paintball gun. Once that was done I constructed an outer casing in which sound absorbing material was inserted. Like most silencers it did not completely silence the gun while firing but it did dramatically reduce the sound. Bellow is a recording of the difference in sound when used with an air cannon. The first shot was with a normal barrel. The second shot is with the silencer. I was firing a .68 caliber paintball in each shot.

Listen to the difference!

The design is actually made for paintball guns, but a larger version could be made easily by scaling up the sizes.  It is very similar to the BOA concealer barrels (retailed for over $90) that are no longer produced.  It is a detachable paintball gun silencer that fits all model barrels.  Very effective and looks sweet! You can purchase plans for the paintball silencer here:

Silencer Plans