Silencer
In British English, silencer is a synonym for a muffler.
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. Some others are designed as an integral part of the weapon, and may include an expansion chamber that partially surrounds the barrel. The silencer reduces noise by allowing the rapidly expanding gasses from the detonation of the round to be briefly diverted or trapped inside a series of hollow chambers called baffles.
Silencers are most effective when the bullet's velocity does not exceed the speed of sound. A bullet that breaks the sound barrier creates loud flight noise, or a "sonic boom". As velocity increases further beyond the speed of sound, flight noise does not increase significantly. Supersonic flight noise may be reduced somewhat by using a projectile of smaller caliber.
Early silencers were created around the beginning of the 20th century by a number of inventors. American inventor Hiram P. Maxim is credited with inventing and selling the first commercially successful models.
Legal regulation of silencers varies widely around the world. In some nations (such as England or Finland) they are practically unregulated and may be bought "over the counter" in retail stores. Other nations (such as Canada) practically forbid their private citizens from owning silencers, while yet others (such as the USA) tax and regulate their manufacture and sale to varying degrees.
