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Thread: Muzzle Blast

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    Default Muzzle Blast

    Talkin bout shootin, here on the Shootin Forum,

    and knowing there are some Scientific Minded folks, and at least one who is Chemically Minded, I seek an answer, (IF THERE IS ONE.)

    Why do we always speak of, and measure Sound, the sound produced or redirected by a Muzzle Brake, or short barrel in terms of Decibels? To the exclusion of other things?

    Are the other things, really significant, or not? I hope this is not too convoluted. There are Two other things I'm asking.

    FIRST, Wouldn't redirecting sound effectively make it closer to the ears? Which would increase its effect to the ears. We know that close sound is more damaging than sound further away. (I rejected the purchase of a SS Rifle, because the barrel was only 20" long. If the rifle had been a BA the barrel would be maybe 4" farther away from the ears, and acceptable to me.) If the SS action was 4" shorter, the barrel would sound more like a 16" barrel to the shooter. ) I hope you can follow that. Let me know if I'm thinkin wrong.

    (Does a Muzzle Brake move the sound closer to one's ears. ) I think Yes, on this one.

    The SECOND question is about frequency, or is it Pitch? It seems to me, that some guns sound more Irritating, on firing than others. I think short barrels sound worse, but is it just because the sound is closer, or is it a different pitch that bothers me?

    Is there no easy way go measure the frequency of the sound produced on firing.

    Thanks, if you can offer me any insight.

    Smitty of the North
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    There's a lot going on here Smitty- I'll try my best.

    First thing to remember is that sound travels in waves, not unlike waves in water. So when those waves are generated further away, the atmosphere attenuates them somewhat. A 150dB blast in close proximity is deafening, a 150dB blast from a mile away is not. The other thing to think about is the angle the waves connect- that's more likely what's happening in a shorter barrel. Shorter barrels burn less powder and powder detonating outside the barrel directs waves more directly back at the shooter. In a longer barrel, the waves generated travel out from the muzzle and can be reflected back at the shooter. That's why firing a rifle on the open tundra is "quieter" than shooting on a crowded range or in dense woods- fewer waves are reflected back at the shooter. That's also why firing a high power rifle inside a building can be astonishingly loud- the sound waves bounce around repeatedly and can effect the ear directly.

    Barrels with brakes direct more gas (and more waves) in more directions and more of those waves come back at the shooter at more direct angles.

    Regarding pitch and frequency- there's a lot of variables there. Some cartridges are more irritating to me than others and have a sharper report than others. My .308 bothers me very little and my .300WSM doesn't either- both achieve nearly 100% powder burn in their barrels. My .270 has a really sharp crack, and likely has the highest MV of anything I own. It's more irritating for sure.

    Once upon a time a buddy have a .338WM chopped to 20" and muzzle braked.... it was awful. Loud as the crack of doom and it threw a ball of flame out the muzzle that would dazzle you in direct sunlight. Not only was it loud- it was the most disturbing rifle I've ever fired. Lots of powder burning outside the barrel and the pressure wave would knock your hat off.
    "I do not deal in hypotheticals. The world, as it is, is vexing enough..." Col. Stonehill, True Grit

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    OK, hodge:

    That sheds some light.

    Come to think of it, I never minded my 30-30s with 20"barrels, even one cut down to 16.5", BUT a 6mm Rem, a higher pressure, higher velocity, cartridge.with 18.5" barrel was murder to my ears.

    I never usta mind shooting my ML without ear protection. Of course, I don't do that now, that my ears have gotten tenderer.

    OK, sounds like the Sharper/Higher Velocity noise, is the kind I'd like to avoid.

    A year or so ago, I encountered 3 young guys with M1As they fired side by side at the same time, and ONE was SOCOM, or whatever you call it, anyway it had a short barrel and porting, I think. Flame from the barrel, was, like you say, "dazzling".

    When I got around to talking with them, he said, yeah it did. I dunno if it affected his shooting, but surely, the other two would be more pleasant to shoot.

    Smitty of the North
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    Not versed in the topic at hand, but is interesting. Some insight can be pulled from this article... might promote additional thoughts.

    Measuring Recreational Firearm Noise...

    http://www.sandv.com/downloads/0908rasm.pdf

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    Quote Originally Posted by bobmikk View Post
    Not versed in the topic at hand, but is interesting. Some insight can be pulled from this article... might promote additional thoughts.

    Measuring Recreational Firearm Noise...

    http://www.sandv.com/downloads/0908rasm.pdf
    Thanks bobmikk:

    That's DEEP. Kinda over my ha'yud, but maybe I can dig something outta there. .

    SOTN
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    I didn't stay at a Holiday Inn last night, and I'm not an acoustic expert. I've seen pictures of the sound pattern from a rifle shot, but can't find one on the web at the moment. If you google search for muzzle blast images, you'll see sort of a heart shaped flame pattern - two lobes centered on the muzzle and a "point" or spear shape going forward from the muzzle center. This is also the shape of the sound pattern. The sound is loudest forward of the muzzle and nearly as loud to the sides of the muzzle. If you've ever had a buddy shoot his shot gun in the duck blind next to your head you've experienced this.

    A tank, but the same shape as a rifle.
    http://en.wikipedia.org/wiki/Muzzle_...zzle_Flash.jpg

    Found this. Shows the gas redirection quite well:
    http://www.ebaumsworld.com/pictures/view/82636870/

    From my understanding, the majority of the sound is caused by the shockwave created by the expanding gasses exiting the muzzle. What the muzzle brake does is redirect those gasses which mitigates recoil. But when the gas envelope is redirected - to the sides - the noise generated by gas expansion is directed back towards the shooter and therefore the noise pattern is substantially redirected towards the shooter and those to the side of the shooter. When guys set up next to me at the range with a big gun and a muzzle brake, I leave. Being to the side I get hit even worse than the shooter with noise and concussion (gas expansion).

    Short barrels tend to "sound" worse because of the increased blast, i.e. powder burning outside the barrel because it is shorter than "normal" - therefore a larger gas expansion plume.

    Another aspect is the "crack" of the bullet (going supersonic). It causes hearing loss as well, but is chump change compared to the muzzle blast.

    The only real affect a short vs long barrel has on noise is that a longer barrel has a higher likelihood of completely burning the gas from the cartridge before the bullet exits the muzzle. With powder burning outside the muzzle on a very short barrel you're basically setting off an additional firecracker with the shot.

    FWIW

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    Quote Originally Posted by Smitty of the North View Post
    Talkin bout shootin, here on the Shootin Forum,

    and knowing there are some Scientific Minded folks, and at least one who is Chemically Minded, I seek an answer, (IF THERE IS ONE.)

    Why do we always speak of, and measure Sound, the sound produced or redirected by a Muzzle Brake, or short barrel in terms of Decibels? To the exclusion of other things?

    Are the other things, really significant, or not? I hope this is not too convoluted. There are Two other things I'm asking.

    FIRST, Wouldn't redirecting sound effectively make it closer to the ears? Which would increase its effect to the ears. We know that close sound is more damaging than sound further away. (I rejected the purchase of a SS Rifle, because the barrel was only 20" long. If the rifle had been a BA the barrel would be maybe 4" farther away from the ears, and acceptable to me.) If the SS action was 4" shorter, the barrel would sound more like a 16" barrel to the shooter. ) I hope you can follow that. Let me know if I'm thinkin wrong.

    (Does a Muzzle Brake move the sound closer to one's ears. ) I think Yes, on this one.

    The SECOND question is about frequency, or is it Pitch? It seems to me, that some guns sound more Irritating, on firing than others. I think short barrels sound worse, but is it just because the sound is closer, or is it a different pitch that bothers me?

    Is there no easy way go measure the frequency of the sound produced on firing.

    Thanks, if you can offer me any insight.

    Smitty of the North
    With regard to measurement, sound is measured in dB because it is a logarithmic unit, which is how your brain processes sounds. It is very sensitive to low sound level and less sensitive to high sound levels, a method of self preservation. dBs basically tell you how loud something is compared to a known reference value, on a logarithmic scale.

    You must keep in mind that sound is simply a wave like any other wave and it is subject to attenuation. In the case of sound waves when shooting the primary attenuator is air, albeit not a very good one. Your ear plugs and ear muffs are much better examples of attenuators. A previous post used water as an example and it is a very good one. If you throw a rock in the water the waves start out big and get smaller the further from impact point, sound works exactly the same way. So the further your standing away from a rifle barrel the more opportunity air has to attenuate that sound. Waves also have directional intensity, which changes with frequency, which is why porting changes the effect on the shooter and those around him.

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    Quote Originally Posted by Smitty of the North View Post
    I never usta mind shooting my ML without ear protection. Of course, I don't do that now, that my ears have gotten tenderer.
    A few years back I woke up in the middle of the night with sudden hearing loss in my right ear. When I went to the doctor he asked me if I had been exposed to any loud sounds recently. I said I had an air hose bust right next to me, but that I didn't think it was even as loud as a 22. He said that was probably what caused it. He also asked what was my history. I told him that in my younger years I used to hardly ever wear ear protection when shooting, was in the construction biz, and also used to play in a rock and roll band as a kid. He told me that a lot of hearing loss doesn't necessarily come from one traumatic event, but can come from years of abuse, and even though something may not sound that significant, all it takes is one more fairly loud noise to push it over the edge. Even though the hose blowing off next to me was a few days earlier, sudden hearing loss can take place some time later. I've regained a bit of my hearing back over the years but no way near all of it. I also ended up with tinnitus in both ears as well.
    Sheep hunting...... the pain goes away, but the stupidity remains...!!!

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    Quote Originally Posted by GD Yankee View Post
    Another aspect is the "crack" of the bullet (going supersonic). It causes hearing loss as well, but is chump change compared to the muzzle blast.
    That interesting because that's not what I've heard. I actually was told that the supersonic bullet accounts for quite a bit of the noise we hear. Even though most lightning bolts look huge, most of them are about the size of a finger, it's the intensity of the light that makes them look so big. So when something that small can cause thunder like it does it stands to reason that a bullet parting the air can make a pretty substantial noise as well.
    Sheep hunting...... the pain goes away, but the stupidity remains...!!!

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    Gentlemen...and Ladies:

    Guns make loud noises.I've fired over 100,000 rounds of center fire ammo...and will (good Lord willin) shoot more.

    Any loud noise...or anything above 90 decibels (think 22 LR) has the potential to cause hearing loss.To some extent, just like losing strength as you age.For those of us at or approaching 70, we can't open some of the jars we used to just twist and hand to our "Missus"..."here ya go".

    No matter what your ear protection program is, if you shoot guns, you will suffer hearing degradation.

    But even if you never fired anything beyond a Red Rider BB gun, old age will also degradate your hearing.

    That is life...and the after effects of a long life.

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    Huh? Speak up, gosh darn it. Can't here a word you're saying!

    At a SHOT show back in the early 1970's or so I could hear shouting all the way across the arena. Figured there was a good argument going on, so drifted over that way. Turned out to be Elmer Keith and Jack Oconnor sitting side by side "talking" and laughing. They were shouting, because sitting right next to each other they still had trouble hearing.

    Funny part was, they thought they were having a "quiet" conversation! The topic of conversation was even more interesting than the two sets of shooting ears. They were talking about how they'd both made a living off the "controversy" of big caliber/slow bullet versus small caliber/fast bullet. Whole lot of laughter, and the rest of us who "happened" to hear their "quiet" conversation were laughing, too.

    After more than 50 years of hunting without ear protection, I can sure relate to their quiet conversation now. What's that you say? Gosh darn it, quityer mummbling and speak like a man!

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    Wikipedia has a very good definition of decibel.

    Shorter barrels are perceived to be louder because the pressure released by the exiting projectile is higher, ergo, the intensity of the blast is higher than that of a longer barrel, and yes, it is closer to the shooter. This can be measured with an instrument placed at the same distance perpendicular to the muzzle.

    What has been stated regarding muzzle brakes is essentially correct, in that, the redirection of the muzzle blast instead of away from the shooter, being perpendicular to the exiting bullet, or with really efficient brakes, back towards the shooter, increases the intensity (pressure), at the ear or instrument.
    Great spirits have always found violent opposition from mediocre minds. The latter cannot understand it when a man does not thoughtlessly submit to hereditary prejudices but honestly and courageously uses his intelligence. Albert Einstein

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    Quote Originally Posted by 4merguide View Post
    A few years back I woke up in the middle of the night with sudden hearing loss in my right ear. When I went to the doctor he asked me if I had been exposed to any loud sounds recently. I said I had an air hose bust right next to me, but that I didn't think it was even as loud as a 22. He said that was probably what caused it. He also asked what was my history. I told him that in my younger years I used to hardly ever wear ear protection when shooting, was in the construction biz, and also used to play in a rock and roll band as a kid. He told me that a lot of hearing loss doesn't necessarily come from one traumatic event, but can come from years of abuse, and even though something may not sound that significant, all it takes is one more fairly loud noise to push it over the edge. Even though the hose blowing off next to me was a few days earlier, sudden hearing loss can take place some time later. I've regained a bit of my hearing back over the years but no way near all of it. I also ended up with tinnitus in both ears as well.
    I had heard hearing loss was accumulative, but I didn't know THAT. The "Details".

    Important stuff to know, that. It explains a lot.

    Thanks
    Smitty of the North
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    Quote Originally Posted by limon32 View Post
    With regard to measurement, sound is measured in dB because it is a logarithmic unit, which is how your brain processes sounds. It is very sensitive to low sound level and less sensitive to high sound levels, a method of self preservation. dBs basically tell you how loud something is compared to a known reference value, on a logarithmic scale.
    OK

    Quote Originally Posted by limon32 View Post
    You must keep in mind that sound is simply a wave like any other wave and it is subject to attenuation. In the case of sound waves when shooting the primary attenuator is air, albeit not a very good one. Your ear plugs and ear muffs are much better examples of attenuators. A previous post used water as an example and it is a very good one. If you throw a rock in the water the waves start out big and get smaller the further from impact point, sound works exactly the same way. So the further your standing away from a rifle barrel the more opportunity air has to attenuate that sound. (Waves also have directional intensity, which changes with frequency,) which is why porting changes the effect on the shooter and those around him.
    Are you saying that,,,, Sound Waves, of a given frequency go will go in a different direction than those of another frequency? Or, am I misunderstanding?

    Thanks
    SOTN
    Walk Slow, and Drink a Lotta Water.
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    Quote Originally Posted by GD Yankee View Post
    I didn't stay at a Holiday Inn last night, and I'm not an acoustic expert. I've seen pictures of the sound pattern from a rifle shot, but can't find one on the web at the moment. If you google search for muzzle blast images, you'll see sort of a heart shaped flame pattern - two lobes centered on the muzzle and a "point" or spear shape going forward from the muzzle center. This is also the shape of the sound pattern. The sound is loudest forward of the muzzle and nearly as loud to the sides of the muzzle. If you've ever had a buddy shoot his shot gun in the duck blind next to your head you've experienced this.

    A tank, but the same shape as a rifle.
    http://en.wikipedia.org/wiki/Muzzle_...zzle_Flash.jpg

    Found this. Shows the gas redirection quite well:
    http://www.ebaumsworld.com/pictures/view/82636870/

    From my understanding, the majority of the sound is caused by the shockwave created by the expanding gasses exiting the muzzle. What the muzzle brake does is redirect those gasses which mitigates recoil. But when the gas envelope is redirected - to the sides - the noise generated by gas expansion is directed back towards the shooter and therefore the noise pattern is substantially redirected towards the shooter and those to the side of the shooter. When guys set up next to me at the range with a big gun and a muzzle brake, I leave. Being to the side I get hit even worse than the shooter with noise and concussion (gas expansion).

    Short barrels tend to "sound" worse because of the increased blast, i.e. powder burning outside the barrel because it is shorter than "normal" - therefore a larger gas expansion plume.

    Another aspect is the "crack" of the bullet (going supersonic). It causes hearing loss as well, but is chump change compared to the muzzle blast.

    The only real affect a short vs long barrel has on noise is that a longer barrel has a higher likelihood of completely burning the gas from the cartridge before the bullet exits the muzzle. With powder burning outside the muzzle on a very short barrel you're basically setting off an additional firecracker with the shot.

    FWIW
    It makes me wonder of what value a Flash Suppressor is.

    Smitty of the North
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    Quote Originally Posted by Smitty of the North View Post
    OK



    Are you saying that,,,, Sound Waves, of a given frequency go will go in a different direction than those of another frequency? Or, am I misunderstanding?

    Thanks
    SOTN
    With regard to frequency, low frequency sound retains volume off axis much better than high frequency sound does. That's why subwoofer placement in sound systems is much less important than tweeter placement, relatively speaking.

    All else being equal, I would expect a break to increase sound level in a rifle with a higher frequency report more than the same break would in a rifle with a lower frequency report.


    Sent from my iPhone using Tapatalk

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    Quote Originally Posted by 7STW View Post
    Gentlemen...and Ladies:

    Guns make loud noises.I've fired over 100,000 rounds of center fire ammo...and will (good Lord willin) shoot more.

    Any loud noise...or anything above 90 decibels (think 22 LR) has the potential to cause hearing loss.To some extent, just like losing strength as you age.For those of us at or approaching 70, we can't open some of the jars we used to just twist and hand to our "Missus"..."here ya go".

    No matter what your ear protection program is, if you shoot guns, you will suffer hearing degradation.

    But even if you never fired anything beyond a Red Rider BB gun, old age will also degradate your hearing.

    That is life...and the after effects of a long life.
    I'll grant you that Old Age will degrade hearing, and perhaps some of that is heredity??

    However, I think you're making TOO LIGHT of the matter.

    I mean, we got people RUINING their hearing, shooting rifles with very short barrels, and 357 revolvers with snub nose barrels, WHICH surely is a LOT worse for the earballs than anything Old Age can do. (Of course, OA will eventually kill you, but that's gonna happen anyway.)

    I wish I knew way back then, what I know now. I'm quite POSITIVE, I'd be better off.

    SOTN
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    Quote Originally Posted by limon32 View Post
    With regard to frequency, low frequency sound retains volume off axis much better than high frequency sound does. That's why subwoofer placement in sound systems is much less important than tweeter placement, relatively speaking.

    All else being equal, I would expect a break to increase sound level in a rifle with a higher frequency report more than the same break would in a rifle with a lower frequency report.


    Sent from my iPhone using Tapatalk
    So, assuming a 300 WM has a higher frequency report, than a 45-70.

    Who bothers with a Muzzle Brake for a 45-70?

    SOTN
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    Quote Originally Posted by BrownBear View Post

    What's that you say? Gosh darn it, quityer mummbling and speak like a man!
    It's certainly true enough, that people who are hard of hearing, talk louder.

    That sounds like something I say to my wife.

    SOTN
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    Quote Originally Posted by 4merguide View Post
    A few years back I woke up in the middle of the night with sudden hearing loss in my right ear. When I went to the doctor he asked me if I had been exposed to any loud sounds recently. I said I had an air hose bust right next to me, but that I didn't think it was even as loud as a 22. He said that was probably what caused it. He also asked what was my history. I told him that in my younger years I used to hardly ever wear ear protection when shooting, was in the construction biz, and also used to play in a rock and roll band as a kid. He told me that a lot of hearing loss doesn't necessarily come from one traumatic event, but can come from years of abuse, and even though something may not sound that significant, all it takes is one more fairly loud noise to push it over the edge. Even though the hose blowing off next to me was a few days earlier, sudden hearing loss can ta I also ended up with tinnitus in both ears as well.
    Those locust singing 24/7 are agrivating aren't they. I am so pitch deaf that I can't hear half the farts I let.

    Smitty , I like short barrels. It helps if you load with a rather fast burning powder. My old 270 had a lot less muzzle blast with IMR 4895 than it did with H4831. I reckon there was a lot less powder being burned outside the barrel with the 4895.

    The loudest rifle I was ever exposed to was a 20 inch 7mm mag. While I am in favor of short barrels with some cartridges a 20 incher on a 7mag would have to be counter productive.

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