silence of the shams

April 16, 2011 6:28 AM

just how unrealistic is a gun silencer as presented in films, something about twice the size of the barrel making a pistol barely audible? how close to the "polite sneeze" sound of a silenced pistol can you get in reality with a similarly-sized muffler?
posted by dong_resin to media & arts (19 answers total)

Depending on the size/design of the weapon, silencers can make a gunshot as quiet as the pin hitting the cap on the cartridge. It's certainly not completely silent (probably around an 80-90% reduction in sound), but it also doesn't sound much like a gunshot, either.
posted by speedgraphic at 6:45 AM on April 16, 2011

http://www.youtube.com/watch?v=ygl9YGM39Kc
posted by speedgraphic at 6:46 AM on April 16, 2011 [4 favorites]

The more accurate term is "suppressor" because the sound is suppressed, not actually silenced. If you want to see how a suppressor is used in a particular film, check the Internet Movie Firearms Database. The folks there often point out suppressor errors.

Sometimes the errors are egregious, sometimes they get it about right. Two huge errors: suppressors on revolvers and suppressors on supersonic rounds. Because of the gap between the cylinder and the barrel, a suppressor doesn't work very well on a revolver. And because of the sonic boom made by a supersonic round, suppressors don't work very well for those either.

In general: "Live tests by independent reviewers of numerous commercially available suppressors find that even low caliber unsuppressed .22 LR firearms produce gunshots over 160 decibels. In testing, most of the suppressors reduced the volume to between 130 and 145 dB, with the quietest suppressors metering at 117 dB. The actual suppression of sound ranged from 14.3 to 43 dB, with most data points around the 30 dB mark."

For comparison, the world record for a finger snap is about 108 dB, but remember that decibels are a logarithmic scale, so 117 dB is ~10 times more than 108. Anyway, a suppressed gunshot will still be louder than an extremely loud finger snap or hand clap.

YouTube videos are tricky because the cameras they're shot with usually have really terrible microphones and, of course, your speakers or headphones aren't going to realistically reproduce a gunshot. Just listen to the unsuppressed part of that video, for example. In real life, standing where the camera is would be painfully loud and likely cause hearing damage.
posted by jedicus at 7:07 AM on April 16, 2011 [3 favorites]

Cracked.com did an article about this sort of thing actually:
http://www.cracked.com/article_18576_5-ridiculous-gun-myths-everyone-believes-thanks-to-movies.html

Here's a brief quote:
An unsilenced gunshot is around 140 to 160 decibels--that's in the range where hearing it once can permanently damage your ears. If you've never had a gun go off next to you, trust us when we say it's loud enough that your whole body will flinch at the sound of it. A silencer can get that all the way down to 120 or 130 decibles, aka the sound of a jackhammer. Still loud enough to cause physical pain if it's close enough to you.
posted by Slinga at 7:31 AM on April 16, 2011 [1 favorite]

Box O'Truth has an interesting discussion of suppressors here.

"A lot of noise comes from the ejection port of a semi. You get a lot of blast and the slap of the bolt is loud.

You might not think so, but in the middle of the night in a field when there hasn't been any other noises for an hour, it's freaking loud..!

For a real quiet shot I hold the bolt shut.

Also you HAVE to use sub-sonic ammo. The rip from super sonic stuff is pretty loud.

And then there is the impact noise.

A lung shot on a wabbit (especially with expanding ammo) is loud in its own right.

So we are pretty far away from the phht noise you get on CSI."
posted by MonkeyToes at 7:57 AM on April 16, 2011

Another issue identified in the YouTube clip referenced above by speedgraphic, but hardly ever made by Hollywood, is that the suppressor fired in that clip is being fired dry. Many, if not most, pistol suppressors that are most effective are designed to be fired wet, i.e. soon after being dipped in water (or oil or grease), to soak the internal baffles and packing enough to further control the escape of hot propellant gases from the firearm barrel. Here's a demo of the preparation and firing of a Glock 21 .45ACP with a "wet" suppressor. Loading up a suppressor designed to be fired wet can get you as much as an additional 20db of suppression, over firing the same setup dry.

And ++ on jedicus comment about the inadequacy of amateur cameras used for recording most YouTube clips, and of computer sound reproductions of such clips, in terms of terrible degraded accuracy of capture and reproduction of shot sounds. To really understand how effective a suppressor is, you have to not only shoot it, but to stand off to the sides, and to the near front of a firearm being shot suppressed by other shooters. Effectiveness of suppression can vary a lot from one axial position to another, as you move around the suppressed weapon being fired.
posted by paulsc at 8:49 AM on April 16, 2011 [4 favorites]

Towards the end of this video there's a demonstration of the Welrod which was a specialist silenced weapon. It was only 73db

I remember a documentary on the French Resistance during WWII that said that with this and similar weapons you could shoot someone in the street without other's hearing become the noise was less than the ambient sounds of people and the traffic.
posted by fearfulsymmetry at 9:27 AM on April 16, 2011

Most pistol suppressors will reduce sound to somewhere around that of a cap gun. That said, some specialized weapons, like those HK integrally suppressed smgs, the de lisle carbine or the russian VSS are said to be incredibly quiet, roughly consistent with those in movie myths. That said, sound and overpressure disperse much more readily out of doors, so even those wouldn't be useful in most movie assassination scenarios.
posted by frieze at 10:01 AM on April 16, 2011

Personal anecdata: in my teens we had a .22 rifle with silencer, and the first time I shot with it I heard the click of the action and wondered why it hadn't fired, but it had (pretty much as speedgraphic said.) Surprisingly silenced! I think a silenced pistol could easily sound like a sneeze.
posted by anadem at 10:29 AM on April 16, 2011 [1 favorite]

I was going to say what jedicus said about revolvers... because of the gap in a revolver, it's like soundproofing a room and then opening the doors and windows.
posted by tel3path at 10:43 AM on April 16, 2011

...but remember that decibels are a logarithmic scale, so 117 dB is ~10 times more than 108.

jedicus, while that's technically true in a power-scale sense, one must also remember that human hearing is also (essentially) logarithmic (as are most human sensory perceptions in general), so decibels actually accurately reflect perception of sound.
posted by IAmBroom at 12:32 PM on April 16, 2011 [1 favorite]

speedgraphic, thank you for your link to that amazing demonstration of noise suppression (www.youtube.com/watch?v=ygl9YGM39Kc).

I NEVER would have believed that much reduction was possible, without seeing that video. Case closed (for me): you can make a sidearm about as noisy as a bad 35mm camera.
posted by IAmBroom at 12:38 PM on April 16, 2011

Shit. Metafilter did something weird with my link (I even double-checked it before hitting "Post Answer"). Go up to the top and use speedgraphic's original link.
posted by IAmBroom at 12:39 PM on April 16, 2011

but remember that decibels are a logarithmic scale, so 117 dB is ~10 times more than 108.

Twice, not 10. It's logarithmic, but with a linear factor of 10 thrown in.
posted by spaceman_spiff at 3:02 PM on April 16, 2011 [1 favorite]

One thing that most movies completely gloss over and that is rarely captured in Youtube clips is the sound of the action. Far, far from the whup, whup sound portrayed as our hero silently takes out the guards, the slide on every pistol (of the many) that I've handled makes a surprising amount of noise. Just "racking the slide" on my HK USP or my Beretta 92 makes a fair racket.

Hollywood usually completely glosses over this. We see our daredevil hero enter the compound, reach into his pocket and quickly screw a suppressor onto his Beretta, and take out a patrolling guard with a faint whup!, while the totally oblivious guard not 20 feet from our hero cleans his fingernails. Absent a ridiculous amount of background noise, every guard within 50 yards would have heard the slide racking as our hero's Beretta ejected an empty casing, and probably heard the ping! as the brass hit the floor, too. Not even Bond-villan guards are stupid enough to not put two and two together when you hear both telltale sounds one after the other.

Sure, put a good suppressor on a bolt-action (or single-shot, or what have you) with subsonic ammunition, and you can wind up with an eerily silent weapon. But on a semi-auto rifle or pistol, when you fire it with a suppressor equipped, the gun is going to make at least as much noise as it does when you rack the action on it.
posted by xedrik at 5:16 PM on April 16, 2011

It is completely unrealistic. They don't get the volume or the actual sound right at all. The real thing depends largely on the caliber and the ammo as well as the quality of the supressor. A 22 is very quiet. You could shoot in the house and a person on the other side wouldn't hear it. A 9mm sounds a lot like a cap gun. Outside with a bit of a breeze it would be hard to hear from 30 yards away. An m16 is still pretty damn loud, but with a suppressor you can shoot it without ear protection. Here is where the ammo makes a big difference. Subsonic ammo sounds much different than supersonic. With the subsonic you can hear the shot clearly, but it is very difficult to tell where it came from. Then there are weapons like the mp5. With a good suppressor you mostly only hear clicking. Overall, there is enough volume even with a suppressor that you could never get away with the stuff in movies. Not even close. But it doesn't sound much like a gunshot either.
posted by jm4 at 6:27 PM on April 16, 2011

Just popped in to point out that there is such a thing as a silenced revolver - the Russian Nagant M1895 gas-sealed revolver in 7.62x38mmR is one and at one point GSG-9 (the German Federal CT unit) briefly used a modified .45 ACP S&W Model 625. Ugly fucking thing it was too from recollection. Bigger suppressor on it than the one on the LaFrance 1911...

The Russians created all sorts of amazing silent weapons during the cold war - amongst the two most interesting are the PSS 7.62x42mm SP4 which used a piston to fire the round whilst keeping the supersonic gasses within the casing and the MSP which used a cartridge firing the M43 bullet from an AK47 to confuse investigators. This site has some excellent coverage of these obscure but interesting weapons.

I've cut and pasted this from elsewhere on MeFi since it's appropriate -

A wet suppressor, as opposed to the dry suppressor used in the video use oil, grease or some other fluid to further abate the sound by cooling and thus reducing the noise generated by supersonic gasses contained between the baffles of the suppressor. It also drips out the end of the suppressor and reduces dust kickup if you're shooting prone which is all good.

The best suppressed weapons are those designed from the get go to be that way - the Sterling L34A1 and H&K MP5SD series used to be amongst the best. Several modern long and short arms use mechanical hold-open devices to prevent the sound of the action "clacking" open and closed when loading or ejecting (the S&W Mark 22 Mod 0 "Hush Puppy" and the H&K Mark 23 Mod 0 are good examples of this). This then requires manual cycling of the action, essentially re-cocking the weapon after each shot is fired.

Other weapons have introduced further adjustments such as adjustable gas vents that reduces ordinary rounds to subsonic velocity regardless of whether a suppressor was mounted. To my knowledge the prototype H&K MP2000 was the first to do so but other specialist firearms are now introducing this feature. Older suppressors used to have extremely short lifetimes. The Mark 22 Mod 0 suppressor could fire less than 10 standard 9mm rounds before the baffles were knacked. Modern suppressors are "maintenance free*" and have lives of 10,000 rounds or more.

I'll recommend the wiki article on suppressors which is surprisingly good and mostly free of bs. I'll "silence" myself right now because this derail is probably really annoying and my knowledge isn't current at all.

*nothing firearms related is maintenance free. Not unless you want something bad to happen...
posted by longbaugh at 1:33 PM on May 4, 2011

Also - since I'm at work at the moment the filters on our internets block all info about gats so if anyone wants to tell the poster about first round pop out of a suppressed firearm you'll probably be able to find some appropriate links for it too :)
posted by longbaugh at 1:35 PM on May 4, 2011

Finally (since I'm now back at work) - the Welrod referenced above came in Mark 1 and Mark 2 models in 9x19mm Parabellum (rare) and .32 ACP (more common) and featured a concave end to the suppressor so that it could be placed flush to the target and on firing the gasses would not be able to escape, further quietening the weapon. As a manual repeater there would be no mechanical noise outside of the pin hitting the primer.

I couldn't comment as to whether this was actually effective or not but the folks at Welwyn labs (Station IX) making the device did very well with everything else they made. I have read that one SOE agent used the weapon in a crowded cinema with the weapon flush to the targets head and this didn't disturb the other cinemagoers although the ambient sound would no doubt be quite signficant and offset the noise.

The Welrod in 9mm was issued to SOG units in Vietnam and was apparently still in the SAS inventory in 1982 during the Falklands conflict. The wiki article linked above also has a sound file of the Welrod being fired.
posted by longbaugh at 5:31 AM on May 5, 2011