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Homework Help: Confused about string instruments and standing waves

  1. Mar 26, 2014 #1
    So I made a banjo for my project and now I need to do the calculations.
    Well since its a string instrument I have to find the frequencies of the first four harmonics, I already have the fundamental frequency.
    Is it fine to use:
    fn = nf1

    Not sure because I thought that was for open end air columns?
  2. jcsd
  3. Mar 26, 2014 #2

    Simon Bridge

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    Science Advisor
    Homework Helper

    Welcome to PF;
    Do not go by equations you find in a book - go by the physics.
    You know that the fundamental and all harmonics must form sine waves - you should be able to sketch a sine wave.

    Your banjo has strings - is the string attached at both ends or just one?
    The attached ends of the string must remain still - so the amplitude there is zero: they are nodes.
    You get an antinode (max amplitude) between every two nodes.
    Each harmonic up adds a node.

    So sketch out the possible sine wave for 2 nodes, then for three nodes, and so on until you see a pattern.
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