Sounds, decibels, and suppressors

A 25-30 decibel reduction is actually a 1,000x reduction in actual sound pressure level.

Sound can be an interesting thing. Especially when referencing sound in firearm suppression. If you’ve been toying with the idea of buying a firearm silencer, and have done a bit of online research, it’s very likely that you’ve come across lots of claims about the “quietness” of certain makes of suppressors. And you probably would like to know that the suppressor you’re thinking of buying performs as advertised. We thought it might be good to make a few references of actual, real-life sounds that most of us are familiar with, to help put things in perspective. These sounds are measured in decibels. So, first of all, let’s talk about decibels.

We measure sound pressure level and quantify it in decibels. Our ears are incredibly sensitive and can hear a huge range of sounds. What our ears are actually doing is detecting changes in sound pressure, and we measure the sound pressure level (SPL) in decibels. Ok, but what exactly ARE decibels? Wikipedia defines the decibel this way:

The decibel (dB) is a logarithmic unit that indicates the ratio of a physical quantity (usually power or intensity) relative to a specified or implied reference level. A ratio in decibels is ten times the logarithm to base 10 of the ratio of two power quantities. Being a ratio of two measurements of a physical quantity in the same units, it is a dimensionless unit.

Now, let’s relate that to the sound we get get from firearms, both unsuppressed and suppressed. The firearm sound levels represented here are absolute sound levels. Instead of adding variables such as the differences between supersonic and subsonic bullets, these examples are simple, realistic, everyday examples of what you can expect to hear when shooting standard velocity (which are most often supersonic) ammunition from guns you’re all familiar with.

First, consider the Daisy Red Ryder BB gun. You probably know what that sounds like when fired. Not too bad, right? It measures in the high-90s. Some more advanced .177 or .22 caliber air rifles will produce volumes up to about 115dB.  Another familiar sound that might help put this in perspective is the sound of a balloon popping close to your ears. It can measure as high as 157dB. But it’s only for a fraction of a second, so while it doesn’t “feel” all that bad, it does produce a high SPL.

The .22LR rifle.

Firing a .22LR rifle (unsuppressed) is considered by some to be the minimum sound level that can be tolerated without using hearing protection. But, from a bolt-action .22LR rifle, the sound can be as high as 140dB with standard velocity ammunition. That’s well above the threshold where irreversible hearing damage begins. Impulse noise beyond 120dB can cause hearing damage, but the limit of acceptable impulse sound according to OSHA is 140dB, so there’s a big margin there. To play it safe, make sure you use some sort of hearing protection if the gun you’re firing will produce sounds exceeding the 120dB level. And by hearing protection, we mean firearm suppressors, of course. What happens to the sound level when you attach a suppressor to that .22LR bolt-action rifle? With a Hughes Precision suppressor, the sound level will drop to around 112db, in some cases, even when shooting standard velocity ammunition. That’s an SPL almost 1,000 times less powerful than shooting unsuppressed. And it’s quieter than some pellet guns.

What about high-power and larger caliber rifles?

A high-power center-fire rifle like the .308 will produce around 167dB when shot unsuppressed. Add a Hughes Precision suppressor, and you’ll bring the level down to the low 130s. That’s the equivalent sound level of an unsuppressed .22LR rifle being fired. And with the added benefit of reduced recoil, that .308 becomes a lot more enjoyable to shoot with a suppressor.

Hopefully, these examples have been helpful in explaining what you can realistically expect when you add a suppressor to your gun.