We’ve all seen it on TV or in the movies: The bad guy slips into the room, hugging the shadows. He glides up behind his target, gloved hands raising the pistol, with a conspicuously long suppressor, and quietly puts two rounds into whomever he’s after. The soft “phhhttt” sounds are barely audible. He then leaves the way he came with no one the wiser. Except, of course, his victim. But how realistic is that? Are suppressors really that quiet? Well, yes and no. There’s more to that question than might be obvious. So, let’s take a brief look at suppressors, how they work, and how effective they might be.
What is a suppressor?
When a gun is fired, the cartridge’s exploding gunpowder creates super-hot gas that forces itself out of the muzzle with the projectile. That gas escaping all at once, combined with the bullet’s sonic boom as it crosses the sound barrier, creates the loud bang that assaults your ears.
A suppressor, or “silencer,” slows down that gas with a series of baffles, cooling it so the noise is considerably reduced. Depending on the gun, caliber, and cartridge, most suppressors reduce the noise signature by 15 to 35 decibels. That may not sound like a big deal, but it is because of how decibels work.
The Decibel Scale
Decibels are not measured in a linear sense. I pretty much flunked math, but a very basic explanation is they increase in a logarithmic fashion, even though our perception of them is different from that. So, a difference of even three or four decibels can make a big difference.
The Federal Occupational Safety and Health Administration (OSHA) says that the 140-decibel line marks the upper limit of “hearing safe.” That doesn’t mean 140 is always comfortable, but it is supposedly safe for your ears. Just for reference, the loudest rock concert on record was 143 decibels. Some concerts in the 130 range have caused bits of the ceiling to rain down on the audience. The average is 115. The average jet engine at takeoff is 140. I don’t know if those are valid comparisons, given the sustained nature of a concert or engine versus the instantaneous sound of a shot being fired, but you get the idea.
What is a firearm’s normal decibel range?
Well, that depends on the cartridge, the load, the gun itself, and whether you’re in an enclosed environment. A 9mm pistol firing in a hallway seems far louder than the same gun firing on an open range. But we can look at averages to get an idea. Here’s a chart of common sounds:
Now, here are some common calibers and firearms for comparison:
- A rifle chambered in .22 Long Rifle: 134 decibels
- A pistol chambered in .22 Long Rifle: 152 decibels
- A .223/5.56 rifle: 155 decibels
- A 12-gauge shotgun or .308 rifle: 156 decibels
- A .45 ACP pistol: 157 decibels
- A 30.06 rifle: 159 decibels
- A 9mm pistol: 160 decibels
- A .357 Magnum or .44 Magnum revolver: 164 decibels
As you can see, firearms are very loud, which we already knew. But as we said, decibels increase logarithmically. Now that means little to me, so I looked it up. Basically, it works like this:
On a linear scale, each unit of value corresponds to adding by the same amount. On a logarithmic scale, each unit of value corresponds to multiplying the previous value by the same amount. On a linear scale, the numbers 1, 2, 3, 4, 5, etc. are equally spaced. But on a logarithmic scale, the numbers 10, 100, 1000, 10,000, and 100,000 are equally spaced, as are the numbers 2, 4, 8, 16, 32, 64, etc.
So, each decibel increase is not a mere single number jump, but rather a multiple of the previous number. Got that? So even a difference of a few decibels is a huge deal. If you look at the above chart, you can see how decibels do not increase in a straight line but create a large curve greater than the numerical values.
Where do suppressed firearms fall on the decibel scale?
Suppressor manufacturers often list the average decibel level of their products. So, I visited the SilencerCo website since they are industry leaders and I’m most familiar with their products. Comparing SilencerCo products to the values listed above, here’s how a quality suppressor can be expected to perform:
- .22 Long Rifle firearms can be reduced from 134-152 decibels to the 108-114 range.
- .223/5.56 firearms can be reduced from 155 decibels to the 128-131 range.
- .308 firearms can be reduced from 156 decibels to the 135-137 range.
- 9mm pistols can be reduced from 160 decibels to the 127-131 range.
- .45 ACP pistols can be reduced from 157 decibels to the 129-137 range.
- 12-gauge shotguns can be reduced from 156 decibels to the 136-137 range.
So, looking again at the chart, even .22 Long Rifle firearms are still as loud as a chainsaw when suppressed. But there are still a few considerations for which to account before we can say how quiet suppressors really are.
Subsonic Ammunition and Cycling Actions
We said earlier that part of the sound of gunfire is created by the bullet breaking the sound barrier. Suppressors do not reduce a bullet’s velocity. In fact, they often slightly increase velocity. The average sonic boom registers 110 decibels. But the sonic boom does not exactly stack with the sound of the escaping gas. If it did, gunfire would register in a monstrous 200-plus decibel range. So, removing the sonic boom helps, but it doesn’t cut the sound by 110 decibels.
A suppressor’s performance is gauged by its suppression of the gas generated when the gun fires. We’ve already seen how that works and what those numbers are. Every one of them is higher than the decibel value of a sonic boom, but removing the boom does help.
Since I’ve thrown lots of numbers at you, let’s look at it this way. If you fire a gun, using a quality suppressor, with subsonic ammo, the cycling action of the gun will be louder than the shot itself. That can even be the case with some supersonic ammo.
On a recent visit to SilencerCo, I fired a .45 ACP 1911 and .300 Blackout chambered AR-15. Both were equipped with SilencerCo’s Hybrid 46M suppressor. I can’t remember whether the .300 Blackout was subsonic or not. Either way, in both cases, the action cycling was louder than the shot. I could hear the projectile hit the dirt berm 30 yards away.
I also fired a lever action rifle chambered in .45-70 Gov’t and a bolt action .338 Lapua Magnum, both using the Hybrid 46M suppressor. Despite the larger calibers and more powerful cartridges, these were even quieter thanks to the actions being manually operated. Again, I could hear the round hitting the berm with both rifles. But were they “whisper quiet?” No, they were not. My companions fired the same guns I did, and I could clearly hear the shots from 30 or 40 feet away. Even the guns whose actions didn’t cycle. The 1911 and AR-15 both gave a loud “clack” as they cycled.
The thing to understand is that they were quiet relative to what I’m used to hearing from a firearm. Grasping the significance of the decibel scale helps too. They were still close to the level of hearing safe, and even louder than an average rock concert. But comparatively, they seemed very quiet indeed.
Understanding Suppressors is Important
Suppressors are awesome. Shooting them outside without hearing protection, as we did in the SilencerCo visit, is fine for a few rounds. But a sustained 130 or so decibels will damage your hearing. Firing a suppressed firearm indoors will be significantly more uncomfortable thanks to the sound being reflected back on you. But it is still far better than shooting unsuppressed.
Suppressors can have a real impact on protecting shooters’ hearing on the range, while hunting, or in a home defense situation. But expecting them to be Hollywood quiet is unrealistic and dangerous. The Hollywood depiction is why suppressors are regulated under the National Firearms Act (NFA). Politicians who knew nothing about suppressors took what they saw in the movies and made a law.
Some modern politicians seek to outlaw suppressors entirely, based on the same wrong information. They claim that not hearing gunfire endangers people who could otherwise escape a deranged shooter. But those politicians are always looking for whatever they think will further their gun control agenda, whether it’s accurate or not.
Suppressors are tools, just like firearms. Used properly, they benefit not only the shooter but those around the shooter. They are used in that capacity far more than they are by criminals. In fact, suppressors are only used in an average of 44 crimes every year. That works out to .003 percent of registered suppressors. And all legal suppressors are registered, thanks to the NFA. Ironically, in gun control happy Europe, suppressors can be bought right off the shelf. Crazy.
So, next time you see a movie depicting silent assassins, or hear uninformed people wringing their hands about suppressors being “assassins’ tools,” think about the decibel scale, escaping gas, and cycling actions. And maybe tell them why they’re wrong.
