Short barrel AR noise levels

[GJM]

In another thread, there was discussion of short barrel AR sound levels in a range setting.

https://pistol-forum.com/showthread....-trends/page10

Another poster and I reported being disturbed by people shooting short AR pistols near us. In the example I gave, my wife and I were down range of the AR shooter, separated by a dirt berm, and the intensity of the shots interfered with our ability to hear our timer's beep and concentrate on the drills we were doing. I was pretty annoyed at the gentleman doing mag dumps of 5.56, out of his shorter than 10.5 barrel AR onto a large piece of steel..... on a pistol bay.

TGS nicely asked if it was age related, and Google says that people with hearing loss are sensitive to loud noises. Between flying and shooting for decades, I am certainly a candidate for hearing loss. The first thing I did was take an online hearing test which reported that my hearing was "normal." The next thing that occurred to me was whether TGS is so young, that his hearing has not fully developed making him more tolerant of loud shots, but I think that is unlikely.

I started Googling short barrel 5.56 decibel levels, and it seems that a 10.5 inch barrel is about 162 db. I couldn't find a number for a 7.5 inch barrel but I assume it is higher than for a 10.5.

https://www.ar15.com/forums/armory/-...460124/&page=1

My experience hunting and firing .300 WM class projectiles without ear pro is that you are best off right behind the rifle. Being to the side or down range of the barrel is worse.

Now for some math and science that I need help with. Let's assume a 7.5 AR is 165 decibels, modestly more than from a 10.5. What will the decibels be to the side or down range. Using a MSA Sordin headset rated at 25 db reduction, does that get subtracted from the 165? How do in ear plugs factor in -- is their db rating added, for example 25 + 30 = a 55 decibel reduction? What kind of noise level will be damaging?

[TGS]

To be clear, the difference between a 10" barrel and 16" barrel is only 2db.

The guns are not significantly louder. They have more concussion, but a 16" barrel will fuck up your hearing or interrupt your shot timer just the same as an SBR.

And yes, thank you for taking that question regarding age in the manner it was intended.

Re:ear plugs, @peterb had posted some articles many years ago about the importance of ear plugs as they absorb certain sound waves which can't be attenuated by muffs. Since then, I make it a standard practice to double up regardless of where I am or what I'm shooting. With plugs and muffs, I feel the concussive "slap" of an SBR, but it's no louder than shooting any other 5.56 rifle.

[GJM]

But aren't increases in decibels like earthquakes:

(From Google) A 1 dB change in a sound equates to about a 26% difference in sound energy (remember that a 3 dB difference is a doubling of energy levels). In terms of subjective loudness, a 1 dB change yields just over a 7% change. A 3 dB change yields a 100% increase in sound energy and just over a 23% increase in loudness.

[Sero Sed Serio]

In no way helpful to the math and science question, but 10 years ago I was comfortable on an indoor range with Sordin ear pro that I believe were rated at 22 dB reduction, even when shooting rifles. Now I double up, foam plugs plus ear pro rated around 30 dab. Even then I find anything super short (in the past month I’ve had the pleasure of being one bay over (indoor) from a 7” 5.56 and some shortened AK pistol-variant with something that mimicked a happy switch and would probably lead to spirited debate with AFT’s general counsel), and both were extremely unpleasant. A year ago I forgot the foamies and just had the muffs, and turned right around and went back outside to rectify that after letting my first .40 round go.

[GJM]

To be clear, the difference between a 10" barrel and 16" barrel is only 2db.

The guns are not significantly louder. They have more concussion, but a 16" barrel will fuck up your hearing or interrupt your shot timer just the same as an SBR.

And yes, thank you for taking that question regarding age in the manner it was intended.

Re:ear plugs, @peterb had posted some articles many years ago about the importance of ear plugs as they absorb certain sound waves which can't be attenuated by muffs. Since then, I make it a standard practice to double up regardless of where I am or what I'm shooting. With plugs and muffs, I feel the concussive "slap" of an SBR, but it's no louder than shooting any other 5.56 rifle.

I would add that after trying different options, my favorite combination is disposable foam plugs under an amplified headset. Some years back, I was told the military did helicopter noise testing and found the best protection was earplugs under a helmet. The helmet protected against damage from the noise hitting the ear bone.

[Totem Polar]

DB is logarithmic. 3 DB is a doubling of sound pressure. Whether we perceive that increase is subject to a lot of psychoacoustic chicanery, but 3db is nothing to sneeze at.


On the subject of HP, I make my living with my ears, and I always foam plug under E-muffs. If you’re indoors, and you are not doubling up, you’re wrong. And, yes, bone induction is a thing. We only have one set of eyes and ears. Best live like that’s the truth. JMO.

[TGS]

I would add that after trying different options, my favorite combination is disposable foam plugs under an amplified headset.

Ditto. I have some pretty robust yellow foamies that peter B blessed off on, and wear those underneath Peltor ComTacs as they have a significantly better fit than my Sordins. Prior to getting this job and being issued the Peltors, I wore Peltor 7s for the same reason even though the electronics on the Peltor 6s and 7s crapped out in impressively quick fashion, whereas the Sordins still work to this day.

[Jim Watson]

Too bad they don't put the Sordin works in a 30 dB cup.
Or do they under another name?

[flyrodr]

Agree with @GJM and others about doubling up with plugs and muffs. And that shooting next to an AR, particularly a short-barreled one, is a pain. Literally. I frequent a nice indoor range owned by the county. It is typical, in that its floors are concrete and walls are block. And the stalls are close, with mesh separations. The RSOs will put up foam sheets against the dividers if you have an AR shooter next to you.

If the RSO forgets and places the loam on your side of the mesh, the blast from an SBR next to you will blow it over, onto you. If it's on the AR shooter's side, it stays put, and reduces the noise slightly. Shooting my scoped rimfire, with front and rear bags, I can watch the crosshairs jump off the bullseye with the AR fires. Not a fan, since most of them are not precision shooters and just like to bang away (although range rules limit shooters to one shot/second).

To be fair, I haven't run into any of the AR shooters to be problematic, so there's that.

On the noise note: Has anyone found a phone app (Android) that is reasonably accurate for measuring dBs?

[GJM]

When I switched optics and put an AEMS on my Rattler, I needed to refine zero on the rifle range. There were a half dozen rifle shooters just finished from a 300 yard match. I gave them the heads up a 5.5 barrel .300 under a shed was going to be ugly. They moved away. With 110 Barnes super sonic, it was nowhere near as bad as being down range of the short 5.56.