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Open/closed air columns experiment

  1. May 30, 2007 #1
    my group was designing an experiment for class where we have to find a length of a column, we started with open, to match a frequency we wanted. we started out with straws, and extended straws, to using the straw as a reed and blowing into a pvc pipe. nothing has worked, our frequency arent what we expect when we use the v=(wavelength)(frequency). we assume that our reed isnt effective, we even tried a recorder mouthpiece, but even the slightest blowing change will mess up the whole frequency. we did get better results with the mouthpiece than the straw. so, is there any suggestions for a reed or a better experiment. we are getting desperate and tomorrow we are going to try an empty wine bottle and do measurements for a closed air column and blow air across instead and hope we get the results we want. we did try playing around with a long closed glass tube and putting a funnel on the open part and blowing across but we were getting high frequencies even though the glass was pretty long. any suggestions to get more accurate frequency readings would be very helpful. thanks
     
  2. jcsd
  3. May 30, 2007 #2

    andrevdh

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    If you hold your ear up against an open pipe in a noisy environment the pipe will "pick" its natural frequency out from among the noise. By holding your ear up against it it changes to a closed pipe though!

    http://en.wikipedia.org/wiki/Pan_pipes

    You can "tune" the length of a pipe by immersing its open bottom end in a container of water. By raising or lowering the pipe in the water its inner length can be adjusted until you obtain the required frequency.
     
    Last edited: May 30, 2007
  4. May 30, 2007 #3
    our teacher did the pipe in the water and adjusted it how far he dipped it in to get the loudest resonance with a tunning fork. I just didn't want to copy that too much
     
  5. May 31, 2007 #4

    andrevdh

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    What may you use as the source of sound? Just blowing over it is rather tricky. Did you look at the link in my previous post?

    You can use a bicycle pump to adjust the length of the column (remove the front end).
     
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