Determining gun loudness

[12Pump]

I've been researching the topic about what makes one gun louder than another for quite awhile and have found something very interesting that I wanted to share, although it may actually be old news to some (maybe even most?). But I thought it was interesting.

I always thought it was about decibels. The higher the decibels, the louder a gun sounds. However, an AR15 with a 16" barrel sounds a lot louder to me than a 12ga. shotgun, even though charts show them to be about the same, with the AR often being maybe one decibel lower. I've also been around short barreled .223 guns that blew me away with the noise they made!

Then I came across an interesting PDF file that shows the decibel range of AR15's with barrels from 5" up to 24" and discovered that the decibel rating is nearly meaningless. It's page 14 of this file: https://ndiastorage.blob.core.usgov...0/armament/WednesdayCumberlandPhilipDater.pdf

There's only a difference of about 2.5 decibels between a 5" barrel and a 24" one, although your ears would tell you otherwise. The sound of even a 10" barrel is in no way anything like a 24". However, check out the pressure ratings in that chart. The 10" pressure is 12,400 and the 24" pressure is only 4800.

It would seem that it's the pressure in the barrel at the time the bullet leaves the muzzle that determines how loud a gun is.

 

[Riomouse911]

I will opine, with no scientific knowledge to back it up, that the smaller bore of the .223 makes for a different pitch than the larger bore of the 12 ga. This sound-pitch difference may also make noise “seem” louder in one gun than another because of how it’s affecting your hearing organs.

I can say the .223 in a 14.5” barrel has a “crack” like sound to me, while the 12 gauge is more of a “boom”.

Maybe out there somewhere is a sound study showing the actual sound signatures of guns to explain it for real rather than just guesses like mine?

 

[12Pump]

I will opine, with no scientific knowledge to back it up, that the smaller bore of the .223 makes for a different pitch than the larger bore of the 12 ga. This sound-pitch difference may also make noise “seem” louder in one gun than another because of how it’s affecting your hearing organs.

I can say the .223 in a 14.5” barrel has a “crack” like sound to me, while the 12 gauge is more of a “boom”.

Maybe out there somewhere is a sound study showing the actual sound signatures of guns to explain it for real rather than just guesses like mine?

I've noticed that too about the "crack" versus "boom" sounds. I find the crack of the rifle to be way more painful.

 

[Deus Machina]

It is, indeed, at least in part the pitch. Some sounds carry better--the difference between instruments in a marching band. Trumpets make themselves known, whereass that bass drum may technically be just as loud, but you feel it more than hear it.
I opine that pressure plays a difference over time. Albeit a fraction of a second, but your ear won't notice a few spikes of a soundwave as much as a few hundred. So the extra time of escaping gasses doesn't cause so much of a decibel difference as a noticed one.

 

[patmccoy]

I think the chart on page 22 is more instructive regarding change in decibels versus barrel length. Also, remember that the decibel scale is logarithmic, so the change from 162.5 to 163,5 is a doubling, and to 164.5 is another doubling.

 

[12Pump]

One thing I don't understand is that if pressure really does determine how loud a gun is, then why does a .45 auto sound louder than a 9mm since the 9mm is a high pressure cartridge but the .45 is a low pressure one.

 

[Double Naught Spy]

so the change from 162.5 to 163,5 is a doubling, and to 164.5 is another doubling.

Loudness (which is subjective) doubles every 10 db.
Sound intensity doubles every 3 db
Sound pressure doubles every 6 db

I don't know of anything that doubles by every decibel.
http://www.sengpielaudio.com/calculator-levelchange.htm

Keep in mind that perceived loudness will vary by location to the event. A shooter is often in the sweet spot (relatively speaking) or sound shadow of the noise discharged from a firearm. A person the same distance from the muzzle but directly to the side of the muzzle will experience the noise at higher levels

 

[SamT1]

It’s all about where the sound is pointed. A flash hider is horrible about making perceived sound behind the trigger louder. While a shotgun had no flash hider usually and a long barrel.

 

[mjsdwash]

I can shoot a 28" 12 gauge all day with no ear protection, get no ringing. Same with a 22 rifle and did for years, and have average hearing. A 16" AR with an A2 hider is horribly loud. I shot a Mini 14 in 223 outdoors without earplugs once or twice, didn't hurt, no ringing, only real difference was the flash hide. hot 357s ring with earplugs in, 22lr pistols are too loud without plugs for me.

 

[mjsdwash]

One thing I don't understand is that if pressure really does determine how loud a gun is, then why does a .45 auto sound louder than a 9mm since the 9mm is a high pressure cartridge but the .45 is a low pressure one.

Pressure vs Volume would be the first guess, but they use similar powder charges, so maybe not. Maybe that slow moving bullets acts like gas deflector and pushes it back at you. My 1911 throws the brass at my face, throws soot at my face, why not? Joking of course.

 

[FROGO207]

If you guys think a flash hider is loud then don't try using a muzzle brake or ported barrel. THEY are loud.As noted DB's are logarithmic so the sound level jumps fast with small number changes.

 

[entropy]

Loudness (which is subjective) doubles every 10 db.
Sound intensity doubles every 3 db
Sound pressure doubles every 6 db

I don't know of anything that doubles by every decibel.
http://www.sengpielaudio.com/calculator-levelchange.htm

Keep in mind that perceived loudness will vary by location to the event. A shooter is often in the sweet spot (relatively speaking) or sound shadow of the noise discharged from a firearm. A person the same distance from the muzzle but directly to the side of the muzzle will experience the noise at higher levels

Like on the next Trap station to the right of someone shooting a ported shotgun. And they are the same guys who raise holy hell if my empties from the 870 hit them. (Which is rare, but it happens.....)

 

[Good Ol' Boy]

No science here either but I concur an AR with a flash hider or even worse a brake is way more uncomfortable than any load out of a 12g outdoors.

My 308 out of a 22" barrel with nothing on the end sounds like a cannon to anyone nearby. Standing 3ft just to the left or right even outside there is quite a bit of noise/pressure felt.

Oddly enough at an indoor range a 223 and 12g sound equally ridiculously loud.

 

[Ironicaintit]

I aint no scientist, but without ear protection, Id rather shoot a 20" 12 ga than a 22 mag mag from a little bitty derringer.

45acp is easy too. 9mm is sorta tolerable, and 357 mag freakin hurts. (learned from misadventures in my youth)

 

[Raybj]

Noticed this years ago,nothing scientific,just my own opinion. If you take a 44 mag, for instance with moderate loads and shoot two loads, one with fast burning powder, and one with slower burning powder, keeping bullet weight and velocity the same I thought that the faster powder had a higher pitched crack that offended my ears more than the slower burning powder.
My experiment used Red dot and Blue dot at aprox 1000 fps loads in 44 mag with cast bullets in a 7 1/2" Blackhawk​

 

[gunlaw]

I can shoot a 28" 12 gauge all day with no ear protection, get no ringing. Same with a 22 rifle and did for years, and have average hearing. A 16" AR with an A2 hider is horribly loud. I shot a Mini 14 in 223 outdoors without earplugs once or twice, didn't hurt, no ringing, only real difference was the flash hide. hot 357s ring with earplugs in, 22lr pistols are too loud without plugs for me.

I agree on the 357 observation. I fired mine without hearing protection once. Sounded like someone cracked a whip by my ear.

 

[Englishmn]

Loudest gun i ever shot without protection was a snub 38 hurt badly. I believe my snub 327 would be louder but im not going to try it.

 

[Deus Machina]

Yeah. Not sure I can offer an objective comparison, because a .38 in a confined space was plenty to leave me completely deaf for twenty minutes or so, and an hour in one ear.
I like to blame concerts, but that's probably a considerable reason for my occasional tinnitus.

 

[.308 Norma]

I believe my snub 327 would be louder but im not going to try it.

I suspect you're right. I'm sorry to say that I know how much my 32 H&R snub hurts when fired without hearing protection. A 327 snub without hearing protection would probably be several times worse.
I'm also sorry to say that I know how much a 7.5" Ruger Blackhawk, 30 Carbine hurts when fired without hearing protection. In my younger years, I gained a lot of experience firing handguns without hearing protection, and lost a lot of hearing!

 

[denton]

Getting good measurements on sound levels requires a bit of care. It's easy to have the impulse overload the microphone and the amplifier chain. The easy way to prevent that is to put the sensor in a sound reducing enclosure. Some components, notably capacitors, in the electronic circuitry tend to be microphonic. You have to protect against that as well.

For power, 10 dB is indeed 10X (or 1/10) the power. A trifle over 3 dB is double or half the power.

Ear protection with 20 dB of suppression cuts sound power levels 100X. 30 dB ear protection cuts it 1000X. 33 dB cuts it 2000X. So there is a big difference between 26 dB muffs and 33 dB muffs.

A change of 1 dB is pretty much imperceptible to your ears.

 

[Mn Fats]

I'm also sorry to say that I know how much a 7.5" Ruger Blackhawk, 30 Carbine hurts when fired without hearing protection.

Same. When I think about it, I believe the day my ears started ringing and never stopped was the day I shot a blackhawk in 30 carbine without hearing protection.

 

[Jim NE]

Very interesting thread. Thanks for posting and for the contributing posts. All I know is that nowadays at an indoor range, I choose to wear both ear plugs and muffs. I think my hearing has degraded a little with age, and I'd like to minimize that.

I kind of cringe when I think of the outdoor target shooting I used to do without hearing protection when I was in my teens and twenties. It was okay with .22 rifles, but it seemed rather painful, or at least unpleasant, with most other guns.

 

[CapnMac]

For workplace hearing safety, there are several measurements. One is "loudness" measured in decibels; there's also "impulse" (which is typically measured as an over-pressure, so in pressure units such as Pascal, Bar, inches of mercury or water column, etc.). Then, there's duration, which is a time measurement.

One of our mods here actually works in this field and can explain better.

But, Loud is bad.
Noisy at high pressure is bad.
Elevated noise for a long time is bad.

Off the top of my head, the OSHA single exposure limit is 140 dB. I forget what the pressure limit is. The exposure limit is in the neighborhood of 80-90 dB for 4 hours.

So, a .44 mag is flat-out loud. Not good for hearing.
But, a .223 while smaller, has more impulse, which is why it seems louder than a .44mag (and does more damage, too)
And, if you worked a shooting gallery tht used nothing but CB caps for 4 hours at a stretch, you coul also have hearing loss, but cumulative effect.

There's a physiological "gotcha," too--the amount of damage is somewhat proportional to age; younger ears are more damaged than older ones. Cruelly, with less perception of that damage, too. So, young people with earbuds in at 75-85dB for 4+ hours a day are doing as much damage as plane spotting at the ed of an active jet runway.

 

[JWF III]

Here’s one that I haven’t been able to figure out. I have 2 Mini-14s with cut barrels and flash hiders pinned and welded at 16 1/4”. The blues steel one has a barrel about 13” and a long M14 style flash suppressor. The stainless one has a barrel about 14 1/2” and an A2 style flash suppressor. The shorter barreled blued one I can shoot, in moderation, without ear pro. The longer stainless one is painful if I forget it for even 1 shot.

If it was the other way around I wouldn’t think about it for a second. I would assume the barrel length as the reason. But as it is, with the longer barrel being worse, I can only assume it’s the material that makes the difference.

Wyman

 

[.308 Norma]

Here’s one that I haven’t been able to figure out. I have 2 Mini-14s with cut barrels and flash hiders pinned and welded at 16 1/4”. The blues steel one has a barrel about 13” and a long M14 style flash suppressor. The stainless one has a barrel about 14 1/2” and an A2 style flash suppressor. The shorter barreled blued one I can shoot, in moderation, without ear pro. The longer stainless one is painful if I forget it for even 1 shot.

If it was the other way around I wouldn’t think about it for a second. I would assume the barrel length as the reason. But as it is, with the longer barrel being worse, I can only assume it’s the material that makes the difference.

Wyman

Strange indeed! Could it be the different style flash suppressors? I don't know much about flash suppressors. That's why I'm asking.