how does a silencer muffle the sound when a bullet is fired?

Answer 1

vivek,

A sound suppressor is designed to be most effective with a given firearm and cartridge. The main purpose of a sound suppressor is to reduce the muzzle blast, which is the most significant portion of the noise. Muzzle blast is caused by high pressure gases suddenly escaping from the end of the barrel into the atmosphere as the bullet exits. Reducing the pressure results in less sound generated. Pressure is reduced by increasing the volume for gas expansion, reducing the gas temperature (cooling), delaying gas exit through trapping and turbulence, and by a combination of these technologies. How well a given suppressor works on a given weapon depends on how efficiently these goals are accomplished.

Answer 2

Imagine a balloon. If you pop a balloon with a pin, it will make a loud noise. But if you were to untie the end of the balloon and let the air out slowly, you could pop it making very little noise. That is the basic idea behind a gun silencer.

To fire a bullet from a gun, gunpowder is ignited behind the bullet. The gunpowder creates a high-pressure pulse of hot gas. The pressure of the gas forces the bullet down the barrel of the gun. When the bullet exits the end of the barrel, it is like uncorking a bottle. The pressure behind the bullet is immense, however -- on the order of 3,000 pounds per square inch (psi) -- so the POP that the gun makes as it is uncorked is extremely loud.

A silencer screws on to the end of the barrel and has a huge volume compared to the barrel (20 or 30 times greater). With the silencer in place, the pressurized gas behind the bullet has a big space to expand into. So the pressure of the hot gas falls significantly. When the bullet finally exits through the hole in the silencer, the pressure being uncorked is much, much lower -- perhaps 60 psi. Therefore, the sound of the gun firing is much softer.

Answer 3

The above answers are good, but I can expand on them a bit. The method used to "delay gas exit through trapping and turbulence" as stated above is to use baffles or mesh packing.

Mesh is very simple to use, but is less effective than baffles. Mesh cools down the propellant gases a lot, but does not create much turbulance or backpressure.

Rubber wipes are very effective for pistol suppressors, but only last several rounds before the X shaped slot in the middle of the wipe is shot through and rendered ineffective.

Better baffles are those that are flat with a hole in the center, cone shaped or a combination of both. These baffles are made of aluminum, steel or inconel and are designed to not touch the bullet as it passes through. The inconel and stainless steel baffles will even endure the high pressures of high powered rifles such as the 338 Lapua, the 50 BMG, or even lengthy bursts from a machinegun. Aluminum which is light weight and easy to machine is suitable for pistol ammunition.

A good suppressor will reduce the noie level by 20 to 30 (100 to 1000 times) decibels. Most suppressors will work even better with a little water or grease added to them to further reduce propellant gas heat by flashing to a vapor. While the noise level is usually much less with the suppressor attached, it may still be above the pain threshold for impulse noise (140 db) and cause hearing damage. Take a look at the below link for noise levels using various silencers.

Answer 4

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