How does a gun silencer work? It seems the noisy part would be on the back of the gun where the hammer hits the bullet, not where the bullet exits. (I know nothing about guns)
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What you hear when a gun is fired is a combination of sounds simultaneously. To keep it simple. 1- is the explosion of gases exiting the barrel as the bullet propels forward. 2- Is when the bullet breaks the sound barrier. (There are more, but will focus on these two sounds) a silencer is meant to absorb the explosion of gases in the first sound. You would then need to also use a lower velocity bullet to reduce the second sound. Unfortunately, movies/TV/games have lied to us, because even with a silencer and low velocity bullet, there is still an audible sound.
The gun is designed such that all the expanding gas from the gunpowder exploding is contained, except for the front of the barrel.
When the gun is fired, all that expanding gas is pushed out the front (along with the bullet). Most of the sound goes out the front with the gas.
There is no such thing as a silencer, they only exist in movies. Suppressors are what make a gun quieter, not silent. When a round is fired the gases behind the round push the round out the barrel. The round and the gases behind it come out the barrel. With a suppressor the round passes through without being impeded followed by the gases. The gases are redirected through baffles which slow down the gases. The suppressor is also made from a metal alloy which disapates the heat of the gases.
The end result is the gases are cooler, moving slower, and less pressure when they exit the suppressor.
There is still a loud noise that can be heard by everyone around. If you try to fire a .44 with a suppressor indoors, but without earpro, you are going to have a bad day
Sound is nothing more than a rapid change in pressure. Guns propel bullets through the use of an explosion, which can be poorly described as a very large rapid change in pressure. The actual mechanical operation of the gun isn’t very loud and the majority of the sound is from the open end after the bullet stops plugging the hole.
The way suppressors work is by extending the amount of time it takes for that rapid change in pressure to reach the open air, usually through a series of baffles that gives a longer path for the gasses to escape through. This makes the rapid change in pressure a little less rapid and because it takes longer a little less strong. This makes it quieter.
Also note that the bullet travelling through the air also makes noise and a lot of ammunition is “supersonic” – that is, it travels faster than the speed of sound. This causes an extremely loud shockwave all on its own, necessitating the use of special low-velocity “subsonic” ammunition if you’re going to use a suppressor.
There are precious few guns that can be suppressed down to hollywood quiet. Most can only manage to be suppressed down from “you must wear hearing protection” to “you could probably get away with not using hearing protection but you probably still should because it’s still quite loud”
The noisy part is definitely not the back of the gun where the hammer hits. That can be heard with trying to fire some empty guns (or dry fire). It’s a click. The bang comes from hot gasses exploding out the front. It’s often compared to popping the cork on a bottle. Behind the bullet there are very hot and expanding burning gasses that come out.
Silencers (or more accurately suppressors, though a company did trademark silencer at one point) spread that expanding energy out over time. An analogy is accelerating a car gently/normally to highway speed vs getting hit from behind and leaving the impact at highway speed. Or popping a balloon vs letting the air out. The end result is similar but the path taken to that new state is different.
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