Then a gun is fired, explosive gunpowder is ignited. The explosive creates a high-pressure pulse of hot gases, forcing the bullet down the barrel.
It exits at a supersonic speed with a bang that breaks the sound barrier.
A gun silencer suppresses that sound. It consists of a tube of small chambers separated by baffles.
When the gun is fired, the pressurised gas now has lots of holes to expand into, so the pressure is far lower when the bullet exits the barrel, reducing the sound.