A suppressor, sound suppressor, sound moderator, or silencer, is a device attached to or part of the barrel

Gun barrel

A gun barrel is the tube, usually metal, through which a controlled explosion or rapid expansion of gases are released in order to propel a projectile out of the end at a high velocity....

 of a firearm

Firearm

A firearm is a weapon that launches one, or many, projectile at high velocity through confined burning of a propellant. This subsonic burning process is technically known as deflagration, as opposed to supersonic combustion known as a detonation. In older firearms, the propellant was typically...

 which reduces the amount of noise

Noise

In common use, the word noise means any unwanted sound. In both analog and digital electronics, noise is random unwanted perturbation to a wanted signal; it is called noise as a generalisation of the acoustic noise heard when listening to a weak radio transmission with significant electrical noise...

 and flash

Muzzle flash

Muzzle blast is the term used to describe the release of high temperature, high pressure gases expelled from the muzzle of a firearm when it is discharged. Muzzle flash is the term used to describe the visible light of the muzzle blast. The blast and flash are caused by the combustion products of...

 generated by firing the weapon.

A suppressor is usually a metal

Metal

A metal , is an element, compound, or alloy that is a good conductor of both electricity and heat. Metals are usually malleable and shiny, that is they reflect most of incident light...

 cylinder

Cylinder (geometry)

A cylinder is one of the most basic curvilinear geometric shapes, the surface formed by the points at a fixed distance from a given line segment, the axis of the cylinder. The solid enclosed by this surface and by two planes perpendicular to the axis is also called a cylinder...

 with internal mechanisms to reduce the sound of firing by slowing the escaping propellant

Propellant

A propellant is a material that produces pressurized gas that:* can be directed through a nozzle, thereby producing thrust ;...

 gas and sometimes by reducing the velocity of the bullet

Bullet

A bullet is a projectile propelled by a firearm, sling, or air gun. Bullets do not normally contain explosives, but damage the intended target by impact and penetration...

.

Early suppressors were created around the beginning of the 20th century by several inventors.