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I Sound: How pleasing to the ear

  1. Jul 17, 2017 #1
    In spite of the prefex I'm not a student, just a very curious person with more than 9 lives to waste :)
    I have a Golden Retriever but she's never been used as a gun dog. She is terified of loud noises like thunder and fireworks, even a distant firecracker will have her shaking for hours. We have a gun range about 2 miles away and while the sound is a little quieter than the firecracker last night she doesn't seem to pay any attention to it. Though I'm not certain, I went to the range about a year ago to renew my range permit and I think there was some shooting then but I just can't be sure. It would be unusual if there weren't.
    Last night I was thinking about why one sound would bother and another would not. My only thought is in the pitch. I've noticed with my own ears that fireworks and thunder sounds more like a boom where gun shots (smaller bore vs shotgun) make more of a snap. I'm assuming because it contains more high frequence sound. So my questions (and there are a few) all related to gunshots not lightning or fireworks:
    • How much of the sound is from the explosion and how much from the projectile exceeding 1100 ft/sec.?
      • If it's primarily the explosion than does the barrel act as a high pass filter?
        • If so than is the barrel length to diamater acting as the z?
        • If you lengthen the barrel (assuming the same mussel velocity, I know it can't) will you raise the frequence cut off, ie is the length to diamater ratio determing the cutoff frequence?
     
  2. jcsd
  3. Jul 17, 2017 #2

    Andrew Mason

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    The shock wave from the bullet will only reach the ears if they are close to the bullet path. So, if the ears are behind the shooter, the shock wave will not register. The sound is from the muzzle blast - the sudden ejection of high speed gases behind the bullet spilling out into the ambient air when the bullet leaves. The exhaust from an internal combustion engine without a muffler provides a similar effect.

      • There is some sound generated within the gun barrel but it is greatly overwhelmed by the muzzle blast.
        • Not sure what you mean by "the z". The barrel length will likely have only a small effect on the sound of the muzzle blast. In order to reduce the intensity of the sound of the muzzle blast, one has to slow the barrel gases before they hit the ambient air.
     
  4. Jul 17, 2017 #3

    scottdave

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    There have to be a lot of factors. This looks like it would be a good basis for a SmarterEveryDay video on YouTube.
     
  5. Jul 17, 2017 #4
    Hi Andrew and Scottdave,

    Andrew: I come from an electronic design background. z in the electronic field represents impedence e.g. an inductor or capacitor as opposed to a resistor which is strictly resistance.

    ScottDave (I assume Dave)
    Yeah I would think so. Somehow the difference in tone has to have a lot more going on. If it's just the gases expanding I would think it would sound closer to a firecracker unless the tone difference is just my imagine.
     
  6. Jul 17, 2017 #5

    davenn

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    I wouldn't entirely agree with that ... yes, it would be suitable for some gunfire, but not all

    but take a small calibre/high velocity example like a .22 calibre rifle the only sound you hear is the "sharp crack" as the bullet breaks the sound barrier as it exits the barrel ( Note, it has already done so within the barrel but we don't hear that breaking of the barrier till it interacts with the air OUTSIDE the barrel)

    from what I have gleaned on a few sites is that the duller BANG that can also be heard ( and will be all that is heard on lower velocity, subsonic, munitions) is the explosion of the "powder" and it will often be travelling at hypersonic velocities and will actually overtake the projectile

    Dave
     
  7. Jul 18, 2017 #6
    Hi Dave.

    That is my experience as well. Definately a higher frequance from the crack. I will have to see if I can set up an experiment. I think taking a single shot .22 pistol (single shot because the only place for the sound to escape is the mussel) and a .22 single shot rifel, and record them both to digital media (to eleminate added artifacts from analog equipment) and examining them with a spectrum analyser. Then repeate the experiment with something larger like a .32 or .38 if I can find pistol and rifel of the same caliber, if I can find such a pair, and repeat it (same conditions). Might be interesting if for no other reason that satisfy my cruiosity.

    Thank you
    Bruce
    P.S.: I like eating cookies in the dark :)
     
  8. Jul 18, 2017 #7

    Andrew Mason

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    So a normal .22 rifle or a handgun that fires subsonic bullets makes no sound?
     
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