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Thread: Muzzle flash photos and sound tests. PWS FFC556 compared.

  1. #31
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    Quote Originally Posted by ToddG View Post
    I have no idea whether a flash hider makes XM193 sound quieter or not.

    But some simple physics: sound is vibration, not pressure, technically speaking. However, sound pressure (the amplitude of the sound wave, which is the difference between the maximum pressure of the wave and the "silent" air) is part of what determines the "loudness" of a sound as we perceive it. In humans, frequency also affects loudness because we perceive different frequencies to greater or lesser extents.

    It's easy to demonstrate that pressure alone is not the same as sound. Jump in the ocean and dive down to about 30 feet. There is a lot of pressure on your ears (more than you'd notice standing in front of a loudspeaker at a rock concert) but not really much sound.

    So a device which is measuring the pressure of a wave might not be giving a perfectly accurate description of the "loudness" being recorded.
    Sound Pressure

  2. #32
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    Quote Originally Posted by ToddG View Post

    It's easy to demonstrate that pressure alone is not the same as sound. Jump in the ocean and dive down to about 30 feet. There is a lot of pressure on your ears (more than you'd notice standing in front of a loudspeaker at a rock concert) but not really much sound.

    So a device which is measuring the pressure of a wave might not be giving a perfectly accurate description of the "loudness" being recorded.
    The human ear is sensitive to pressure changes that occur in the range of approximately 20 to 20,000 cycles per second. My sound meter has a weighting filter which approximates the response of the human ear. If my sound meter indicates that it is louder, then it probably is.

    "Loudness" is a term having to do with human perception and is subjective. Any loudness meter is supposed to correspond to what we (meaning the average person) can hear.

  3. #33
    ToddG Guest
    Quote Originally Posted by Trim2L View Post
    Loudness

    edited to add: This corresponds to what rsilvers is saying about a sound meter that corrects for frequency.

  4. #34
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    This is a good reference:

    http://hyperphysics.phy-astr.gsu.edu...d/loud.html#c1

    dBs are a logarithmic measure of SPL (sound pressure level) and are units used for loudness.

    Linear sound pressure is measured in Pascals. You can do conversions here:

    http://www.sengpielaudio.com/calculator-soundlevel.htm

  5. #35
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    Quote Originally Posted by ToddG View Post
    Loudness

    edited to add: This corresponds to what rsilvers is saying about a sound meter that corrects for frequency.
    Sure, but sound is measured by its pressure. DB is a measurement of weight.

    Quote Originally Posted by ToddG View Post
    But some simple physics: sound is vibration, not pressure, technically speaking.
    Sound is the interpretation of pressure by the human ear.

  6. #36
    ToddG Guest
    Quote Originally Posted by Trim2L View Post
    Sure, but sound is measured by its pressure. DB is a measurement of weight.
    Sound is measured by many different things. Pressure is one of them.

    Sound is the interpretation of pressure by the human ear.
    Loudness is the interpretation of pressure and frequency by the human ear. Sound itself is vibration, which is different than pressure, and exists whether or not there is a human ear around to hear it.

  7. #37
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    This all related back to flash. I am thinking I can hear the flash combustion.

  8. #38
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    Quote Originally Posted by rsilvers View Post
    This all related back to flash. I am thinking I can hear the flash combustion.
    There is only one way to know for sure, I'll hold the rifle while you put your ear right next to the muzzle.

  9. #39
    ToddG Guest
    Quote Originally Posted by Trim2L View Post
    There is only one way to know for sure, I'll hold the rifle while you put your ear right next to the muzzle.
    That's such a Spicoli thing to say!

  10. #40
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    Quote Originally Posted by ToddG View Post
    That's such a Spicoli thing to say!
    My dad is a TV repairman and he has an awesome set of tools!

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