How does a silencer on a gun work

A.� By controlling the rate that the gases that propel the bullet expand. They're normally called sound moderators or suppressors.

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Q.� What are silencers made of

A.� There are numerous designs, but basically a silencer is really just a group of baffles (a plate that diverts the flow of liquid gas or sound waves) along with an expansion chamber. The whole thing screws onto the end of the gun.

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Don’t be too swayed by Hollywood's portrayal of silencers, they’re often quite bulky and awkward to fit, a far cry from the slick compact tubes toted by actors. Even the celluloid version of the sound of a silenced gun is fanciful: rather than the discreet ‘phut’ a real silencer produces something much more like the slam of a car door.

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Q.� What creates the noise a gun makes when it goes off

A.� The noise of a gunshot is made up of the propelling gases that expand quickly after leaving the muzzle along with the 'crack' of the sonic boom of the bullet. For more information on how sonic booms work, click here.

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The expanding gases have energy, which is recognised as a loud noise. The expansion chamber dissipates this energy and allows the gas to cool off. The baffles then slow down the flow of gas as it leaves the expansion chamber.

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Q.� But the gun still makes some sound even when a silencer is fitted..

A.� Yes, because silencers can only moderate one element of the noise a fired gun makes: the expanding gas. For a silencer to be really effective they need to be used on guns whose bullets travel slower than the speed of sound.

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Some silencers are designed to slow a bullet down to subsonic speeds.

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Q.� Can silencers be fitted to any gun

A.� Yes, apart from revolvers, where the gap between the barrel and the silencer is sufficient to allow enough expanding gas to escape to deliver a bang as the shot is fired.

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by Lisa Cardy