A silencer or suppressor, is a firearm accessory designed to reduce the amount of noise generated by firing the weapon. The silencer is typically a cylindrical piece of machined metal that attaches to the muzzle of the pistol or rifle. It acts as an extension of the barrel, and reduces noise by allowing the rapidly expanding gasses from the detonation of the round to be trapped inside a series of hollow chambers called baffles. The turbulence from this activity slows the bullet marginally, but a properly designed and fitted silencer should not noticably interfere with the operation of the gun at most ranges. Silencers are less effective with high velocity rifle ammunition that breaks the sound barrier, because the sonic boom left in the bullet's wake is louder than the initial chemical explosion. Silencers are illegal in America and most developed countries and cannot be used without a special license.