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Sound Travel in a Vacuum (not the obvious question)

  1. Jun 12, 2008 #1
    Hi, I'm new here. I got referred here when someone else couldn't answer my question. Hopefully, someone can answer the question. Thanks in advance for taking the time.

    I have a vacuum thermos. Somehow, a bottle cap wound up in there. I was walking with it, but I could still hear it jingling around just fine- plenty loud.

    I thought sound can't travel through a vacuum

    Is this what's happening? The sound energy has to go somewhere so it all leaves- just through a different path?
    Below is a cross section of the thermos (green= cap, black = walls, red = vacuum).

    So it's just as loud, just taking a different path? In theory, if middle container was "floating" (didn't have to be attached to the outside walls), you wouldn't hear anything, right? Since there is a solid path (or at least a path not broken up by vacuum), does the vacuum provide any (significant) "r-value" (if it was analogized to heat transfer)?

  2. jcsd
  3. Jun 12, 2008 #2


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    The sound is being transmitted via mechanical vibrations in the steel inner vessel transmitted via the seals to the outer shell. Also there is the air in the thermos itself which can transmit sound.
  4. Feb 19, 2009 #3
    hi sound itself will not travel within the vacuum, the noise itself is purely down to the mechanics of the compont touching the edge of the container http://www.absolute-vacuum.com/resources.php [Broken]
    Last edited by a moderator: May 4, 2017
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