Crack and Bang

Discussion in 'Other Accessories' started by Kellen, Oct 26, 2020.

  1. Kellen

    Kellen G&G Evangelist

    A while back I had to manage a long-term project that involved monitoring of noise levels. That’s when I learned about decibels, and there sure was a lot more to it than I realized. For gun folk, the word usually comes up in the context of muzzle brakes and suppressors. If any of you find the following info helpful then I’ve done my good deed for the day…

    “Deci” is a prefix meaning one-tenth of something, and decibel is one-tenth of a Bel. A Bel is a unit of measure named in honor of Alexander Graham Bell. Since decibel is derived from a proper name the abbreviation for decibel has a capital “B”, as in “dB.”

    Decibels are measured on a logarithmic scale which usually extends from 0 to 140 (it can go higher). The scale’s zero point is the threshold of what a human can barely hear, or barely not hear. As a logarithmic scale, each increase of 10 is ten-times more powerful. So 70 dB is ten-times more intense than 60 dB, 80 dB ten-times more than 70 dB, etc. In human terms, that 70 dB sound will seem about ten-times louder than 60 dB, and 80 dB will seem ten-times louder than 70 dB.

    Most people think a decibel is limited to measuring acoustics, but it is also used as a unit of measure for perception, telephony, electronics, optics, videography, radar, antennae, bandwidth, amplitude/clipping, noise temperature, etc.

    When a gun fires, three basic actions occur. Primer compound explosion, conversion of powder from a solid to gas, and resulting propulsion of a bullet through the barrel. All three of those actions make noise, and to use plain speak I’ll say there is both a “bang” and a “crack” noise.

    The “bang” initially comes from ignition of primer compound (a small amount of high explosive chemicals), but more so from the sudden release of gas pressure out of the cartridge. Similar to a bottle of champagne making a low-level bang when uncorked, the sudden release of gas pressure from a cartridge can make a very loud bang. Suppressors are good at dampening the “bang” from gas pressure.

    The “crack” occurs from the shock wave a bullet makes when it breaks the sound barrier. Usually that is around 1,125 feet per second (depending on atmospheric conditions). Most bullets travel at least that fast at the muzzle; even a 40-grain 22LR typically travels at 1,250 fps. This means even the diminutive 22LR bullet can “crack” as it breaks the sound barrier.

    Since the “bang” and the “crack” happen so fast from the perspective of the shooter, they essentially combine to make a very loud noise – loud enough that ear damage could result. Even a single shot could result in some permanent hearing loss without ear protection.

    “Quiet ammo” (aka subsonic ammo) achieves lower sound levels by both reducing the amount of gas pressure and keeping the bullet below 1,250 fps to prevent sound barrier “crack.” For example, 22LR ammo marketed as quiet might leave the muzzle at just 710 fps. In a semi-auto, quiet ammo may have pressure so low that it can’t sufficiently cycle the action. And importantly, best not to confuse “quiet” with silent. It is usually recommended that you still wear ear protection with quiet ammo (though others will argue that point, depending on the cartridge).

    It’s the more typical loud firing noise that makes us interested in things like muzzle brakes, suppressors, and hearing protection. That is where decibels come in. (When it comes to muzzle brakes, we also need to differentiate between sound pressure and concussive blast, but that’s too much of a side track to go into here).

    As a general point of reference, the little 22LR will produce around 134 dB. The 308 around 156 dB. The 45 ACP comes in at 157 dB. 30-06 around 159 dB. A 357 or 44 magnum around 164 dB. And a 12-gauge hits 165 to 170 dB. The shorter the firearm’s barrel, the higher the dB. To put those sound levels into perspective, a crowded restaurant is usually around 70 dB, a lawn mower is 90 dB, a chain saw is 100 dB, an emergency siren typically runs at 115 to 120 dB, and an aircraft carrier deck is around 140 dB. (See comparisons at

    Audiologists consider human hearing damage to begin at 85 dB. Studies by the American Speech-Language-Hearing Association (ASHA) have shown that people like us, firearm users, are more likely to experience hearing loss, usually at higher frequencies. You’ll notice that happening when you start losing the ability to distinguish sounds like “s,” “th,” or “v.” Right-handed shooters suffer more damage to their left ear, which is more in line with the muzzle, than their right ear. Shooters may also develop tinnitus, or permanent ringing in their ears.

    When we’re at the range we’re all smart enough to wear hearing protection, right? Ear muffs will reduce noise between 15 to 33 dB. Look for the NRR number (noise reduction rating); higher is better. But consider, if you’re firing a magnum rifle or handgun around 160 dB or more, and your ear muffs reduce it down to 130 dB, that’s still hazardous to your ears. I recommend you wear earplugs in addition to muffs. And on top of that, a suppressor would help. The federal government should eliminate regulation of suppressors as a safety measure in order to allow more shooters to better protect their hearing.

    However, what about when we’re hunting? If you’re like me you don’t wear hearing protection when hunting; I want to hear Mr. Bear when he’s in my neighborhood. Even if we’re not the person firing the gun, our hearing can be damaged by someone next to us who fires at game. Again, it takes only one shot to cause damage. I guess that’s just part of the price of hunting.

    Audiologists are more interested in ear damage than just sound pressure, so they use “dBA” which is “A-weighted decibels.” dBA is intended to focus not only on what the human ear can actually hear, but also on how sound can damage the human ear. Consequently, many regulatory noise limits are specified in dBA. When we read about noise impacts from firearms, dB is not as helpful as dBA, but unfortunately there is very little (if any) data regarding firearms and dBA.

    I’d be really interested to hear perspectives from an audiologist if we have one who is a GNG member.

    (Note: The original post had an error, sort of, indicating 22 LR produced 152 dB. That is the correct dB level for a 22 LR pistol, but a 22 LR rifle is the better reference, and that is 134 dB. That dB level has been corrected above and the online reference source added for clarification.)
    Last edited: Oct 26, 2020
  2. Ten Man

    Ten Man G&G Evangelist

    Crack and Bang

    The title made me think of the recent exposure of the Hunter Biden scandal with his accessories.
    jedwil, Junction15, neophyte and 5 others like this.

  3. I am confused. If (as you day) the scale goes from 0 to 140, how can a .22 LR produce 152 dB?
  4. Brandhard

    Brandhard G&G Evangelist

    Same here. I assumed this was going to be a political thread.
    neophyte, BigEd63 and Ten Man like this.
  5. Ten Man

    Ten Man G&G Evangelist

    Careful reading would have avoided the confusion.
    AK Hunter, chesterwin and TXplt like this.
  6. TXplt

    TXplt Gun Toting Boeing Driver Forum Contributor

    The above.

    And I don't think that's correct.

    Perhaps when measured from a very short barrel revolver.

    I'd say my MP-15/22 is closer to the 130 range at the muzzle. Other than the supersonic crack from the bullet, my M4s suppressed are really close to a .22LR.

    A typical suppressor gives you around 30db of reduction but it does vary.

    And alot depends on which way the sound is going; it's not omnidirectional (brakes are a good example of this). Nonreflected outdoor sound pressure at muzzle away from ears is significantly better than shooting indoors close to dividers in a concrete building.

    We'd refer to the 3 db point as the half power points when I was in electrical engineering looking at signals. A drop of 3db was close to half the original power.
    chesterwin and Ten Man like this.
  7. The deck of an aircraft carrier is at 140 dB
    A .22 is 152 dB.
    A .22 is TEN TIMES louder than the deck of an aircraft carrier.
    A .22 is FIFTY TIMES louder than a chain saw (100 dB).

    That's what we are supposed to believe. Seriously?
  8. Ten Man

    Ten Man G&G Evangelist

  9. chesterwin

    chesterwin G&G Evangelist

    I don't know the db. levels of chainsaws, rifles, shotguns, handguns, weedwhackers, jet planes, speedboats and etc. I do know that after over half century of exposure, without hearing protection mostly, I've got one heck of a case of tinnitus and probably a small amount of actual hearing loss. My hearing is still fairly acute despite the tinnitus, a little selective these days though.
    Ten Man likes this.
  10. neophyte

    neophyte Wonderment :) Forum Contributor

    information: Sound defines

    Comparing Sound Power and Sound Pressure
    Sound power is the acoustical power, sometimes expressed in watts, generated by a source of sound such as a hydraulic pump. Two sound sources (pumps) could be compared by their relative acoustical wattage outputs, but can be more conveniently compared by assigning decibel ratings on the dB power scale.

    Sound pressure is the strength of the traveling soundwave, in PSI or other pressure units, at a specified distance from the source of the sound. Discomfort or damage to a listener's ears is from sound pressure, not from sound power at the source. Although two sound waves could be compared by their PSI as read on a sound level meter, it is more convenient to compare them on the dB pressure scale. This is a different scale than the dB power scale on which acoustical wattage is rated.

    The dB scales for expressing and comparing sound power and sound pressure were arbitrarily selected so as to be convenient to use. The two scales are different but were carefully defined so their relationship to each other would be such that a change of (so many) dB on the power level at the source would result in the same dB change in pressure reading at any distance from the source. Instead of a linear scale, dB ratings were placed on a logarithmic scale to compress the upper end into a more usable and practical range.
    EtherialOne likes this.
  11. Thanks for the Info, Having a good bit of hearing loss and Tinnitus this Rings Very True (pun intended).

    A couple of thoughts from the my perspective working 20 years in Aviation Maintenance (military) with 16 years of Aircraft Engine Testing.

    Tinnitus and Hearing Loss S*cks! ... And for those working around Operating Gas Turbines especially Aviation it is Impossible to not have hearing Loss. I can tell you that I always wore both ear plugs and muffs or what we called "Crainials" (what you see folks on the flight decks of carriers wear) when working with Operating engines so yea, about 40 dB worth of "Protection" but the truth is you will still suffer hearing loss.

    When I was onboard a Carrier I had a Medic who was the ships NAVOSH (Navy Osha) program manager do a survey of my work center Test Cell. He wanted to get readings for an Engine being tested which happened to be a TF-30 P414a the Engine that all but the last variants of the F-14 Tomcat used. His meter went to 140 dB. We Started up, did our Idle leak checks and as soon as we accelerated to 80% N2 Compressor Speed (Idle was 70%) He flagged us and said he was done... His meter was Pegged. He Left and Never came back! Now this was on the Fantail of the Carrier, so Inlet noise from the compressor was reflected off the Ships structure with the tail of the engine literally hanging over the edge of the fantail so Exhaust noise had nothing to reflect off of. The truth is that at higher power settings you cannot protect yourself because the sound pressure is damaging your hearing right through your Skull. Even when working on the Ramp on Shore an F-14 at Idle 75 yards away has a cone of Noise coming from the inlets that's damaging with hearing protection on at certain angles. So just be aware that depending on your occupation Sometimes the Only thing you can do is to limit the damage by minimizing exposure time as much as possible, which we all did, even though we weren't as informed as we should have been.

    Also I probably don't need to mention it, considering the Audience but if you spend a lot of time at the range and shoot rifles with muzzle attachments choose your add on carefully. Brakes generally port gas out the sides to mitigate recoil while compensators tend to be designed more to help prevent muzzle rise and port out the top and Flash Hiders to do just that ... minimize muzzle flash, at least in their purest form. You'll often see the terms used interchangeably on sales web sites, and the truth is that many muzzle devices are designed to do two or more of these so generally I tend to look at the design to get an Idea of what it's going to do. If you do a lot of outdoor range shooting it's not a bad Idea to get a Compensator that vents forward vs. to the side's or up which don't do anything for Muzzle rise or Recoil, but they do help to direct sound downrange and away from you which is a good thing since you get less direct noise exposure and more reflected noise softened by distance and trees etc. Obviously if you are at an Indoor range this effect is negligable.
    Ten Man and neophyte like this.
  12. Ten Man

    Ten Man G&G Evangelist

    For the years I was flying jets, I never suffered tinnitus, nor had any hearing loss, because I always had ear plugs in under my helmet or ear muffs. Same when flying civilian aircraft, but I did not always have ear plugs in. When I started shooting a lot, the high pressure sound exposure went way up. It was even worse than jet noise. I tried to protect my ears as much as possible, but there were unintentional exposures to very loud, high pressure gun shot noises. It just comes with the territory when working at the range.

    In the last 5 years, with less shooting, and no flying, I have developed tinnitus. It is a combination of 3 high pitched tones, in both ears, 24/7. Loud or sharp noises aggravates it. So far, there's no discernable hearing loss, but I'm sure it's coming. The adverse hearing effects are an accumulation of exposure incidents, much like radiation exposure.

    Getting old is a mixed bag, but it beats the alternative, so far.
    EtherialOne likes this.