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Mythbusting Silencers

Here’s a brain teaser: What’s louder, an old-school alarm clock (smartphone alarms don’t count for this exercise) or gunshots using silencers? To make this easier, you can count either the normal weekday alarm volume or the special Monday morning version. While we may not understand the underlying science, we all know Monday morning alarms are, in fact, measurably louder. Got an answer? Gun silencer or alarm clock? If that first one was too easy, how about the comparison between a balloon popping and a firearm suppressor? Let’s explore.

The Science of Silencers

The science behind gun silencers (it’s also correct to call them suppressors) is actually pretty straightforward and can be explained by a party balloon.

Imagine blowing up a balloon and, assuming you have reasonable finger dexterity, tying a knot to keep it sealed. Now, pop it with a pin. What happens? That’s right. Bang! You cause the family cat to seek treatment for PTSD. Can cats benefit from service dogs? I guess that’s a question for another day, so back to balloons.

Now, imagine filling up that same balloon, but instead of tying a knot, hold the “nozzle” closed with your fingers. At your leisure, gradually let the air out. While you might hear some hissing or noises reminiscent of gross bodily functions, you won’t hear a loud bang.

Congratulations, you’ve just made a silencer using your fingers. Since there’s no gun present, the ATF won’t even be hunting you down.

Pressure Not Fire

The “why” behind this may be a little surprising. You might think the noise of gunshots is related to the “explosion” (really just a very rapid conflagration), and it is, but not because of the flames and such. Just like the balloon example, the noise of a gunshot results from the rapid equalization of pressure levels.

An inflated and sealed balloon contains air at a greater pressure than what surrounds it on the outside. When you pop it, the high-pressure air rapidly expands, creating a big noise. In the other scenario, when you release the balloon’s air gradually, there is no sudden release of pressure, so there is no significant noise.

Gas and Silencers

When you shoot a gun, a massive amount of high-pressure gas exits the muzzle all at once. Ipso facto E. Pluribus unum, lots of noise.

A silencer does nothing more than help slow down the release of that expanding cloud of gas as it exits the muzzle. Internal baffles in the silencer encourage the gas cloud to swirl around a bit and even cool down, at least a little, before it makes its way out the muzzle end of the silencer tube. Simple, right?

How Loud Is a Silencer?

Given the volume of gas and the speed of the underlying chemical reaction that causes a bullet to fly, a silencer can’t be as effective as slowly releasing the air from a balloon, but it sure does help.

For example, a common handgun creates about 160 dB of noise level at the muzzle. When a suppressor is added, that level is reduced to about 130 dB. That may not sound like much, so it’s important to remember decibels are measured on a logarithmic scale so that 30 dB reduction doesn’t lower the sound by 18 percent, but rather orders of magnitude. Explaining the scale another way, going from 10 dB to 20 dB doesn’t double the noise; it increases it by a factor of 10.

So, Silencers quite gunshots a lot, but how does that compare to other common noises?

Noise Comparisons

Let’s consider some actual sound-level examples to set perspective.

A gunshot in a Hollywood movie, detective series or the nightly news is, as we all know, 0 decibels. Miraculous, isn’t it?

The dramatic whispering by that same action movie’s hero is about 30 dB. That’s a real number. A normal human-to-human conversation measures about 60 dB.

Got a lawn? Your gas mower creates about 107 dB, while a chain saw delivers about 120. Even a car horn (up close) measures 110 dB.

That Megadeath concert you saw in high school would peak around 115 dB.

Even your old-school alarm clock ruins your morning with 80 or more dB.

Myth… Busted

So, what have we learned? A suppressed gunshot is significantly noisier than lots of really loud things like chainsaws, jackhammers and car horns. The next time you watch a movie and don’t hear the gunshots, you can call foul with confidence.

Oh, about that balloon pop? One Canadian study measured the peak level of a popping balloon at a whopping 168 dB. There’s a lot more to “loudness” than the instantaneous peak level, so you don’t have to boycott birthday parties. On the other hand, it’s probably not a good idea not to stab balloons right next to your ear.

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2 Comments

  1. I find disagree with what has been reported here.
    As a long time end user of suppressors (the actual
    Correct name) I would however add that powder amount, bullet design and most importantly the muzzle velocity of a shot effect the sound signature out of a suppressor. If a round is Sub Sonic as it leaves the muzzle it will have a real as well as preserved increased reduction of the sound signature over a round that is traveling faster than the speed of sound (Sonic) will have.
    Also various types of baffles, length an diameter of the can will also effect the sound signature as well.
    If one is to consider performance it should be considered as fully as possible.

    Thank you,
    Pete sends…

    • As a long-time member of the firearms industry, I have to disagree with some of your disagreements 🙂

      While I agree that “suppressor” is more descriptive of what the device does and the more commonly used term today, “silencer” is the correct name of the device — that’s what’s on Hiram Maxim’s 1902 patent for the very same device we’re talking about here.

      As for sound, you are correct; supersonic ammo is “louder,” but that’s only because of the second sound source, the sonic “boom” of the projectile. But all that doesn’t change what this article is about – the relative volume of suppressed gunshots being far louder than what most people assume according to Hollywood portrayals. That and the fact that it’s the rapid reconciliation of vastly different pressure levels of the expanding propellant gas and surrounding air that causes most of the noise. That’s why larger-caliber airguns are quite loud too. The dB levels quoted in the article are, in fact, accurate.

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