Suppressors; those sneaky dBs; and your hearing...

This is a discussion on Suppressors; those sneaky dBs; and your hearing... within the Defensive Rifles & Shotgun Discussion forums, part of the Related Topics category; Suppressors seem to be in 'vogue' now. Some people call suppressors, silencers. Suppressor is really more technical correct, but silencer is well established. I prefer ...

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    Suppressors; those sneaky dBs; and your hearing...

    Suppressors seem to be in 'vogue' now. Some people call suppressors, silencers. Suppressor is really more technical correct, but silencer is well established. I prefer suppressor, but have no problem with silencer either. The real question is do you really want one for your AR, and if so, why?

    As you read this, you should be aware that I just bought a SureFire Socom 5.56 suppressor and Surefire compensator/adaptor. So about a year from now, I may be able to take possession of it. One suppressor at the gunshop I bought my suppressor from has been 'in waiting' for 8 months now. .

    Let's start with the bottom line. I did some research about suppressors and found overall they reduce muzzle blast, i.e. specifically muzzle blast, they do nothing to reduce super-sonic blast, but they reduce muzzle blast by about 30 dB. How much is that? It's about the same as a good pair of gun muffs. That's right, a good pair of gun muffs and a suppressor reduce muzzle blast sound pressure striking the ear by the same amount. Hence, one might jump to the conclusion that they are essentially equivalent - one would be wrong about that. The muffs also reduce super-sonic 'boom' where a suppressor does not.

    To see how effective that 30 dB reduction really is, we need to know two things: one the sound pressure level (SPL) of an AR and the SPL that can cause permanent damage to the ear. Let's start with the latter. Again, an internet search revealed that SPLs above 140 dBs can cause ear damage. And further research shows that's not a fixed value, but can vary some from individual to individual.
    The SPL of rifles vary from about 150dB to 165 dB. An AR purportedly has a muzzle SPL of about 160 dB. So if we put a 30 dB suppressor on an AR (5.56/.223) the muzzle blast should be reduced to about 130 i.e. 160 dB – 30 dB = 130 dB. Well, 130 dB is well below the threshold of damage, 140 dB. But, 130 dB is LOUD. Normal speech is about 65 dB. Well, that could imply that the suppressor has reduced the muzzle SPL to about twice the level of normal speech, i.e. 2 x 65 dB = 130 dB. Well because of those sneaky little dBs, things are not as they might seem.

    The dB scale is logarithmic, meaning very small changes can produce very large changes. For example, how much louder is that 130 dB than 65 dB? We do subtract 65 from 130, but here’s where the catch is, we then have to divide the difference by 20 (twenty) and then raise 10 (ten) to that, like this:

    130 – 65 = 65
    65 / 20 = 3.25
    10 ^ 3.25 = 1778

    That means that the muzzle blast coming out of the suppressor is 1,778 times louder than normal speech – hardly a ‘silencer’ is it? However, how much did the 30 dB suppressor reduce the 160 dB muzzle blast by? This one is one step easier because we already have the difference – 30 dB. Soooooo, we just divide 30 by 20 = 1.5 and raise 10 to that power:
    10 ^ 1.5 = 31.67 or about 32 times quieter. It’s still really loud though.

    Here’s another tricky thing: we don’t hear SPL correctly. This gets a bit deeper. Regardless of the initial dB value, if you increase the dB level by 6 dB, it actually doubles the SPL. E.g. 16 dB is twice as loud as 10 dB (6 dB difference); likewise 126 dB is twice as loud as 120 dB; 97 dB is twice as loud as 91 dB. Each of these examples represent a 6 dB change and a doubling effect. But here’s the tricky part – our ears don’t hear it that way.

    We ‘hear’ a 10 dB change as doubling! That’s due to the nature of our hearing. The problem is, that 10 dB represents a 3x factor in sound pressure, and it is the sound pressure that damages our ears, not our perception of the sound. So if we hear a sound and it is increased until we perceive it as twice as loud as the original sound, the sound pressure has actually increased by 3.

    But all of that is true for suppressors or muffs. So the question remains, does a 30 dB suppressor reduce the SPL to a level that will NOT damage our hearing. I can say without reservation the answer is MAYBE. We also have to add to the muzzle blast, the SPL of the super-sonic boom. We have to add indoor or outdoor environment. We have to add anything that could cause more sound to be reflected/deflected to our ears. But then that’s true of muffs as well, except for the sonic boom which the muffs do suppress and the suppressor does not.

    So why was it you wanted a suppressor for your AR?

    Well, it’s pretty cool for one thing. And it’s well known that us Americans value and buy “cool”. But one of the applications I see a suppressor as a big asset is for hunting. Hunting can be extemporaneous - we’re moving and listening with the anticipation of hearing or seeing game and shooting it. Well ‘hunting’ and shooting may be inversely related. I.e. if we want to hear, we can’t have our hearing impaired by muffs or plugs. If we want to shoot, we don’t want to expose our ears to an extremely loud muzzle blast. Hence the ‘best’ solution – a suppressor. The suppressor will quite the muzzle blast to a one-shot safe level/duration – more about that in a minute. That means we don’t need muffs or plugs at all – for a one or two shot situation such as hunting.

    As if it wasn’t complicated enough, there’s also the one-time exposure that does not permanent harm, vs the same sound level repeated many times. This complication addresses the level-duration-repetitive issue. It turns out that peak SPL, which is what we’ve been talking about, is by no means the whole picture. The duration of the sound has as much effect as the peak SPL. What this means is that a sound that has the very same SPL but lasts twice as long can do more damage than the shorter duration sound. Further, that one or two shot ‘hunting’ exposure that is not harmful, can become harmful if we shoot the same SPL repeatedly. So the number of shots and how much they are separated in time is also a significant factor.

    Lastly, there is ample evidence that shows that damage caused by loud sounds is not linear. That is, higher level sounds do more damage than the ratio of the SPL. E.g. if we are subjected to a 150 dB sound and then a sound level twice as loud, i.e. 156 dB, the damage that may be done to the ear is more than twice, even though the sound level only doubled.

    So, for me, outside I would feel safe using a 30 dB suppressor on an AR without muffs or plugs in a hunting application where only one or two shots would be fired. But even outdoors, I would be reluctant to shoot 50 – 100 rounds with the suppressor alone. But this does give options. Right now I shoot an AR with both muffs and plugs. However, the suppressor could be used in combination with the muff or plug and be almost as safe as muffs and plugs.

    I speak from experience here – don’t assume. I now wear hearing aids because I have typical shooter’s hearing, i.e. tinnitus and a loss of high frequencies which makes it difficult to understand words that contain high frequency components. Hearing loss is permanent. You can have temporary loss which you can recover from, but once damage has been done it is irreversible and non-fixable except with hearing aids and that’s not nearly as good as natural hearing.

    Realize that high sound levels for short periods of time may not be harmful at all, but if you are exposed to them for longer periods of time, those same sound levels can produce permanent damage.

    Be careful about using your hearing to judge sound levels. Remember it takes a tripling of sound level for us to hear what appears to be twice as loud to us. It is the actual sound pressure that does the damage. So what might sound safe, may not be.

    Rifles are loud – always use ear protection. Even suppressed rifles are loud. Based on the 140 dB SPL being the threshold of damage, a rifle with a muzzle blast of 160 dB, reduced by 30 dB by a suppressor should be safe, but that really doesn’t take into account sonic boom which is not suppressed, nor does it account for the guy beside you shooting an unsuppressed rifle.

    Take care of your ears – once they’re damaged, there is no recovery. There is no treatment, surgery, etc. that can restore any hearing loss – you live with that for the rest of your life.
    I'm too young to be this old!
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    Good write-up, Tangle. The logarithmic effect of the DB scale is overlooked by many. Although, one doesn't need an algorithm to understand LOUD after standing next to the muzzle of an AR.

    I'm pondering suppressors for subsonic munitions these days.
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    Good information. The dB scale is not what it seems, unless you have an understanding of logarithmic scales.

    As someone who can attest to the hearing damage caused by one exposure to a .357 magnum at 160+ dB, I recommend wearing some protection even with a suppressor.

    Some people still shoot handguns or rifles without any protection when outdoors, which is quite foolhardy, in my opinion.
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    Quote Originally Posted by WHEC724 View Post
    Good write-up, Tangle. The logarithmic effect of the DB scale is overlooked by many. Although, one doesn't need an algorithm to understand LOUD after standing next to the muzzle of an AR.

    I'm pondering suppressors for subsonic munitions these days.
    Don't know if this would be of interest to you or not, but JIC...

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    For me, the main use of suppressors is with teams, so it's easier to identify who is shooting.

    For me, my 11.5" gun is short because that's what I prefer for vehicle and structure use. Since hearing protection is needed indoors with most barrel lengths, I don't gain much with a suppressor not working with a team. If I were to ever put one on that gun, and I'm not ruling it out, it'll be a Surefire 5.56 SOCOM mini.

    I may switch my 9" 300 blackout over to a work rifle at some point. I've been thinking hard about picking up a Surefire 7.62 Mini. My main reason for this would be hunting, nothing more. As of now, I'd run it without the suppressor for work.

    Don't get me wrong, I'm a huge fan of suppressors. I just think many people misunderstand their intended use and what roles they fill best.
    Proven combat techniques may not be flashy and may require a bit more physical effort on the part of the shooter. Further, they may not win competition matches, but they will help ensure your survival in a shooting or gunfight on the street. ~Paul Howe

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    I couldn't follow the math--the ringing in my ears is too loud. My hearing loss is from 20 years of jet engines as well as a healthy contribution of gunfire. Ear plugs and/or ear muffs just will not protect from some noise. And the damage is accumulative--a little today and a little tomorrow adds up until one day you have to ask, "What did you say?" Twice...
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    Quote Originally Posted by jonconsiglio View Post
    ...Since hearing protection is needed indoors with most barrel lengths, I don't gain much with a suppressor not working with a team.
    Exactly how I see it.

    Quote Originally Posted by jonconsiglio View Post
    ...I may switch my 9" 300 blackout over to a work rifle at some point. I've been thinking hard about picking up a Surefire 7.62 Mini. My main reason for this would be hunting, nothing more. As of now, I'd run it without the suppressor for work.
    Sub-sonic BO would be an interesting platform for sure and hunting and suppressors seem to be a really good fit.

    Quote Originally Posted by jonconsiglio View Post
    ...I just think many people misunderstand their intended use and what roles they fill best.
    Yeah, I the marginal suppression level (ear-wise) is part of that. A suppressor on an AR just doesn't quite do enough to eliminate the need for some kind of ear muff/plug.

    I bought the full length suppressor because that extra 3 dB suppression is more significant to me than compactness. That extra 3 dB of suppression gives 41% more reduction in SPL.

    I'm going to go shoot my G17 now
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    Quote Originally Posted by OldVet View Post
    I couldn't follow the math--the ringing in my ears is too loud. My hearing loss is from 20 years of jet engines as well as a healthy contribution of gunfire. Ear plugs and/or ear muffs just will not protect from some noise. And the damage is accumulative--a little today and a little tomorrow adds up until one day you have to ask, "What did you say?" Twice...
    I know exactly what you mean!!!

    I didn't have the exposure to the jet engines, but I understand the accumulative effect.
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    Quote Originally Posted by OldVet View Post
    I couldn't follow the math--the ringing in my ears is too loud. My hearing loss is from 20 years of jet engines as well as a healthy contribution of gunfire. Ear plugs and/or ear muffs just will not protect from some noise. And the damage is accumulative--a little today and a little tomorrow adds up until one day you have to ask, "What did you say?" Twice...
    Same here OV same here. I fully intended to read OPs post in it's entirety till I got to the trigonometry part and I just couldn't. Sorry. I only watched half of the video but all I was interested in was seeing/hearing what effect the full suppressor would have with that rifle. I was shocked nay flabbergasted this was a 308 rifle!!! Unbelievable!!! Sounded like a 22 short out of my High Standard Sentinel w/5 1/2" barrel or an air rifle.

    I 'll say this for that scent hider. That stuff works like gangbusters!!! I couldn't believe how close the shooter got to those feral hogs. I've read about feral hogs a few times in my life and until now I wouldn't get within what looked liked under 50 yards of one with a BA rifle let alone 4 of those 4 legged monsters!!

    The only other question I have is does feral hog taste about the same as farm raised pork or bacon? Pass the BBQ sauce please!

    edit to add: I finished watching the video and am glad I did. I got a charge out of the answer the hunter gave the woman from back east, Maryland was it? His answer the 2A protects all of the other amendments. The 2A is NOT about hunting it's about protection from evil men. Whether you're talking about gang bangers or Schumer evil men/women are all around us.

    I would LOVE to have my 22 carbines suppressed. When the ATF gets out of the suppressor business I'll go get one. As long as I have to fill out an ATF form and wait 12-18 months+ pay a $200 tax just to have one suppressor I'm just NOT interested.
    Firing a suppressed is on my Bucket List.

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    Greetings from another hearing impaired oldster. How I wish we knew 50 years ago what we know now. Untold numbers of rabbits, potguts, deer, pheasants, grouse, and about any other critter are now celebrating for the sacrifices of their ancestors to make me hard of hearing. Revenge is a plate best served cold. The only way it could get worse is if God turns out to be a spider or an ant. Then I'm toast forever.

    Oh, now I wear sport ears nearly all the time. On and off the range. I still carry an extra set of ear protection in the car for those lonely parts of the highway that just scream, "Pull off the road a ways and shoot something".
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    Spiders? Ants? Don't you mean earwigs Farsidefan? What in Sam Hill is a 'potgut'??
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    Firing a suppressed is on my Bucket List.

    I'm just a spoke in the wheel but not a big deal.

    America...a Constitutional Republic. NOT a democracy as the liberals would have us believe.

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    Suppressors; those sneaky dBs; and your hearing...

    NONAME62, you should hear a suppressed 300 blackout. You can hear the action perfectly. It's just a solid, quiet thud. I have no use for them really, but it is fun at first.

    I don't currently own a 308 suppressor, but hope to at some point. The Surefire SOCOM 762 mini is the same size as the standard SOCOM 556, and it works just as well on 5.56 rifles as the SOCOM 556 does, so that MIGHT be my next suppressor. If I buy another 5.56 suppressor, it'll probably be the SOCOM Mini. Since an 11.5" with standard SOCOM 556 is not hearing safe anyway, I might as well opt for the shorter of the two.
    Proven combat techniques may not be flashy and may require a bit more physical effort on the part of the shooter. Further, they may not win competition matches, but they will help ensure your survival in a shooting or gunfight on the street. ~Paul Howe

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    It only takes on shot. A friend had complete hearing loss in his right ear after 1 round from a .357 Bain & Davis. Custom molded plugs for the skeet field, plugs and muffs for rifle and pistol. I cant afford to lose any more hearing. Grand Funk Railroad and Deep Purple concerts messed up my hearing long ago. No mathematics was required, just the physical science on the proper use of rolling papers.
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    Quote Originally Posted by NONAME762 View Post
    ...I fully intended to read OPs post in it's entirety till I got to the trigonometry part and I just couldn't. Sorry.
    There's a lot more mathless info - you could just skip the math stuff.

    Quote Originally Posted by NONAME762 View Post
    ...I only watched half of the video but all I was interested in was seeing/hearing what effect the full suppressor would have with that rifle. I was shocked nay flabbergasted this was a 308 rifle!!! Unbelievable!!! Sounded like a 22 short out of my High Standard Sentinel w/5 1/2" barrel or an air rifle.
    Just to be sure, you realize he was shooting sub-sonic ammo? That means a .308 bullet at about 1/3 it's normal velocity.
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    I often hunt without ear pro, which I know is a bad idea... But at 100 degrees, electronic muffs are bothersome and plugs don't allow me to hear the others I'm with or the animals in wooded areas nearly as well.

    Shooting with the muzzle out the window of the truck, it's not that bad. Recently I got out and found one of the hogs still moving. So instead of finishing it with my 14.5" 5.56, I shot it with my Glock 17.

    I had worse ringing in my ears from that 17 than my 5.56. I fired one shot from the Glock and usually fire a string from the 5.56 since we often drive up on big groups of hogs.

    Indoors, the 5.56 is always louder, but something about the area we were hunting mDe the 9mm really sharp. If we didn't hunt in tight, hard to maneuver wooded areas or from the trucks, I'd be more likely to use a short suppressor. Even the one ranch I hunt with large open fields, there are still right wooded areas and we're still out driving. Every time I've gone out with a suppressor, I've wanted to remove it after half of the first day.
    Proven combat techniques may not be flashy and may require a bit more physical effort on the part of the shooter. Further, they may not win competition matches, but they will help ensure your survival in a shooting or gunfight on the street. ~Paul Howe

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