suppresor

A silencer, also known as a sound suppressor, suppressor or sound moderator, is a muzzle device that reduces the acoustic intensity of the muzzle report (sound of a gunshot) and the recoil when a gun (firearm or air gun) is discharged, by modulating the speed and pressure of the propellant gas from the muzzle and hence suppressing the muzzle blast. Like other muzzle devices, a silencer can be a detachable accessory mounted separately onto the muzzle, or an integral part of the barrel.
A typical silencer is a metallic (usually stainless steel or titanium) cylinder containing internal sound baffles, with a hollow bore to allow the projectile (bullet) to exit normally. During firing, the bullet flies through the bore with little hindrance, but most of the expanding gas ejecta behind it is retained through a longer and convoluted escape path created by the baffles, prolonging the release time. This slows down the gas and dissipates its kinetic energy into a larger surface area, reducing the blast intensity, thus lowering the loudness.Silencers can also reduce the recoil during shooting, but unlike a muzzle brake or a recoil compensator, which reduce recoil by vectoring the muzzle blast sideways, silencers release almost all the gases towards the front. However, the internal baffles significantly prolong the time of the gas release and therefore decrease the rearward thrust generated — as for the same impulse, force is inversely proportional to time. The weight of the silencer itself and the leverage of its mounting location (at the far front end of the barrel) will also help counter muzzle rises.
Because the internal baffles will slow and cool the released gas, silencers also eliminate the muzzle flash. This is different from a flash suppressor, which reduces the amount of flash by dispersing burning gases that are already released outside the muzzle, without necessarily any sound or recoil reduction. A muzzle shroud, on the other hand, conceals visible flashes by screening them from the direct line of sight, rather than reducing the intensity of the flash.

View More On Wikipedia.org