Also known as a
Sound Suppressor. Some people call it a "can" as it does resemble a tin can. Can be detachable or integral to the firearm.
Tactical sub machineguns like the
MP5SD (the SD is from
Schalldämpfer, meaning "
sound dampened") series have an integral suppressor. Tactical pistols like the
USP Tactical or
Beretta 92SD have a removable flash suppressor.
The removable type attaches to the
muzzle part of the barrel via screwing in to threads or locking lugs.
For all intents and purposes a Flash/Sound Suppressor and a silencer are one and the same. Devices whose sole purpose is to reduce muzzle flash signatures are called flash hiders.
Do not be mislead by the term "silencer", a suppressed firearm is in no way silent (when firing of course). An MP5SD5 firing 9mmx19 NATO ammunition for example will have its sound signature reduced to levels similar to that of an unsupressed .22, which is still quite audible. A suppressed .22 lr though is truly whisper quiet.
The point of a Flash/Sound suppressor is one, to minimize or eliminate muzzle flash both for the purpose of not blinding the operator and also to hide one's position from the adversary, and two, to make the report of firing the weapon sound distinctly different from the sound of a weapon being fired. In an MP5SD in full auto, the sound is more like a rapidly reciprocating pneumatic device rather than a firearm discharging. Sound suppression is best done with subsonic ammunition (like the .45 ACP) as supersonic ammo will still have a loud crack from the sonic boom that the bullet creates in its wake.
Well known brands are Knight Armament Co. and the Swiss made Brügger&Thomet who makes suppressors for everything from pistols to shotguns.