Tuesday, January 17, 2012

Silencers, don't.

And really, who doesn't love James Bond movies?

The problem is that the movies, if anything, exacerbate the already egregious firearms errors found in Ian Fleming's books. (Fleming wrote brilliant thrillers; weapons just weren't his area of expertise.) But, back to the movies...

How many times has a character, Bond or otherwise, used a silenced handgun? Probably too many to count. Silencer use is typified by this clip from Goldeneye (click on the image to view):
Of specific interest is the sequence from 0:30 to 0:33. Let's forget for a moment that Sean Bean's character, Alex Trevelyan, is using a Browning BDM, which, anachronistically, wouldn't be produced for another five years after the fictional scene's 1986 date, and instead concentrate on that tube at the pistol's muzzle end.

For years, audiences have been conditioned to recognize that "tube at end of pistol = silencer" and "silencer = really quiet shot."
I suppose that in batting averages, a .500 isn't bad. But with respect to technical accuracy it's unacceptable.

(Read that "Epic Fail!")

In other words, a tube-like extension at the end of a pistol is probably a sound suppressor of some sort ("Silencer" is actually a trademarked term that grew beyond its initial usage, much like "ketchup" has displaced the use of "catsup."), but suppressors do NOT change the sharp crack of a pistol shot into a muffled "Puh-TEW." A suppressed gunshot sounds a lot like....a gunshot.

We'll hold off on a technical discussion of how suppressors work for another post and look strictly at the numbers.

To begin with, the power or intensity of sound is measured in decibels (dB). With reference to acoustics, a decibel is commonly used as a reference to quantify sound levels relative to the threshold of average human sound perception, or 0 dB. That's thing one.

Thing two is that the average suppressor dampens sound by about 30 dB, and an exceptional suppressor will diminish the intensity of sounds by as much as 43 dB.

That's good, right? The answer is that you don't have enough information to make an assessment. Yet.

Thing three is a bit of data from which to make the assessment:
  • Normal conversation, taking place about one meter away is about 50 dB;
  • A passenger car driving by around ten meters away is about 70 dB;
  • A jackhammer operating one meter away is about 100 dB;
  • Threshold for risk of hearing damage is 120 dB;
  • Pain threshold is 130 dB;
  • .45 ACP pistol being fired one meter away is about 157 dB; and
  • 9x19mm (9mm NATO) pistol being fired one meter away is about 160 dB.

What's it all mean?

It means that even if you have one of the super-duper, highly efficient suppressors that reduces sound level by 43 dB for your character's 9x19mm pistol - from 160 dB to 117 dB, the gunshot's report is still significantly louder than a nearby jackhammer.

(And that's LOUD, folks!)

Add into the mix the mechanical sound of the pistol's moving parts and the sonic boom created by the bullet as it breaks the sound barrier and things aren't very stealthy. At all.

The question then becomes "If a suppressor doesn't silence the sound, why use it at all?"

There are a number of answers, but essentially they boil down to:

  • The suppressor minimizes the pistol's report;
  • The suppressor changes the sound so that it is less recognizable as a gunshot; and
  • The change in sound pattern caused by the suppressor helps to disguise the shooter's location.

So, while suppressors most emphatically do not "silence," they do provide valuable acoustic camouflage for the shooter.

How do I like my suppressors? Shaken, not stirred, of course.


  1. So, Adam, if a suppressor doesn't really suppress the sound of a bullet, I take it a pillow isn't going to do the job either?

  2. Well, anything that slows or contains the hot, rapidly expanding gas escaping from the gun's muzzle when it is fired will muffle the sound to some extent - but a pillow will certainly not come close to eliminating the report.

  3. Thanks, Adam. I've seen that (the pillow-as-silencer) in a couple books and TV shows. Another myth bites the dust!

  4. Adam, I really like this technical information on how guns and their accessories work especially in the context of a popular movie. Looking forward to your technical discussion on how suppressors actually work.

  5. Something I took for granted--I thought silencers = silence. Thanks for the information and looking forward to hearing more.