1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: How to determine harmonic number

  1. Apr 6, 2013 #1
    1. The problem statement, all variables and given/known data

    I have 8 pipes for a school project taped together to make a pan flute, they are 7, 9, 11, 13, 15, 17, 19, 21 inches... 1 inch diameter each one. I have to find the frequency of each one, but I'm not sure what the Harmonic numbers are. It is an open-ended instrument. I plan to use as a percussion instrument, using my hand, hitting the ends of the pipe to create sound.

    2. Relevant equations

    F = Hn * V/2L
    F: frequency
    Hn: Harmonic number
    V: speed of sound traveling through pipe assume 343 m/s
    L: length of pipe sound is traveling through

    3. The attempt at a solution

    I'm not sure how, as I do not know how to find the harmonic number, my teacher just gave us a project to make a pvc pipe instrument and a formula for Open-ended, stringed, and closed instruments. The teacher does not expect questions on anything....

    Not sure how to attempt without harmonic numbers...
  2. jcsd
  3. Apr 6, 2013 #2
    I am not sure about what you are trying to do, but looking at that formula, I do not see a problem in just plugging integers to compute the frequencies for each pipe. Hn=1,2,3...
  4. Apr 6, 2013 #3
    I just don't know what Harmonic numbers are. I didn't know whether to make the smallest pipe 1 or the longest pipe 1.. I need to use that to figure out the frequency of each pipe so that I can then determine the note.

    Sorry I can't really provide much information, but all I was looking for was a good explanation as to what harmonic numbers are. We don't have a textbook or anything in notes and such to explain harmonic numbers.

    But I think I get it. longest pipe should be lowest number and smallest pipe longest number. Since the smaller it is, the higher the frequency I believe..... (I don't know anything about notes, waves, harmonics, etc.)
    Last edited: Apr 6, 2013
  5. Apr 6, 2013 #4
    The harmonic numbers are 1,2,3.... for all pipes they are not determined in any way on the length of the pipe. So you can compute the fundamental frequency i.e Hn=1 for each of the pipes just by using f=v/(2L). If you need the other harmonics just plug Hn=2,3,.... For each pipe you get 1 fundamental and a series of harmonics.
  6. Apr 6, 2013 #5


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    From each pipe you can get a fundamental note and, potentially, higher harmonics. From the OP, it seems to me that all you care about are the fundamentals, which you can compute from the formula you have, setting Hn=1. The length of each pipe dictates its fundamental and higher harmonics independently of the other pipes.
    If you want to learn more about harmonics anyway, try http://www.physicsclassroom.com/Class/sound/u11l5c.cfm.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted