Audio Question: distance of gun shots

Discussion in 'XDTalk Chatter Box' started by the yetty, Jul 5, 2006.

  1. the yetty

    the yetty XDTalk 100 Member

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    I saw some posts here that explained different noise levels of different guns/bullet calibers. I have also seen the chart.

    My question is.....

    How much does the noise drop per foot / yard (or whatever measureing distance). My questions arose because I was at the range the other day (outdoor range). I was in the back area, about 50-60 yards away from a pistol shooter who was at the front end of the bay. I was not wearing hearing protection when he begain to fire, and although it was loud, it was not painfull or nearly as loud as being right next to a gun. Soon after that he backed up more and started to unload his ar-15 about 15-20 yards away. This was substantially louder and I quickly put on my ears.

    This leads me to the question of how far away is an average distance that is safe to not wear hearding protection?

    Next question, how much does the terrain effect the distance the sound of a shot travels? For instance, I would assume that in a desert the sound of a shot would travel further then in a hilly wooded area where there is more of a dampening effect.

    I know there are several members here that have experiance and knowledge in the audio arena. Thanks in advance to anyone that responses.

     
  2. TomSwift

    TomSwift XDTalk 1K Member

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    Technically it's a 6db drop everytime you double the distance (in feet) from the source, but a little further reading lead me to find that you start the measurement 50 feet from the source. Experience told me that you couldn't get a 6 db drop two feet from the muzzle if you started the measurement at 1 foot.. So, if you measured the muzzle blast at 50 feet and got, say, 96 db, then at 100 feet you would drop to 90 db. 3 db is the minimum change the most people can detect. I know some mastering engineers here in Nashville that can detect 1 db changes but they are the exception (and yes I have done a double blind test with one of them and yes he can detect a 1 db change). There are other factors that could effect the results, such as, berms, trees, hills, wind, etc.
     
  3. the yetty

    the yetty XDTalk 100 Member

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    Thank you for your reply,

    I have been wondering about this for some time.

    I have not done any measuring of gun shot noise level at any distances, but I think the average level of a gun shot at the muzzle or close to it is around 140db

    If I understand it right, noise levels above 82, you need hearing protection if its prolonged. And you shouldn't be exposed to noise levels over 115 without hearing protection.

    So if I took your example, I am assuming that a realitiving safe distance for no hearing protection would probably be 100 yards. And that would be if its not a prolonged exposure.

    Would this be a safe assumption???
     
  4. CyberOtaku

    CyberOtaku XDTalk 100 Member

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    Sound (as well as other signals) weaken by the inverse square. Wher S2 is the sound at the source and r is the distance from the source.
    S2 = S1/r^2
    For instance if the distance (r) is tripled the noise level drops to 1/9 (1/3^2). Of course, if you are somewhere where the sound will bounce off of objects or the sound is focused in one direction the noise drop will be different.


     

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