Does temperature affect pitch?

  1. This may seem like a fairly simple question, but I want to know if the temperature of the air affects the pitch of a note produced by say an instrument or by someones voice? I play guitar and I know that if I leave my guitar in the cold for too long (or the heat) the tuning gets all messed up. I also know that air temperature affects the frequency of a note but I'm not sure if frequency and pitch are the same thing. Clarification would be much appreciated, Thank You.
     
  2. jcsd
  3. DaveC426913

    DaveC426913 16,374
    Gold Member

    Yes.

    And yes, frequency and pitch are effectively the same thing. (Frequency is a physical measurement of the cycles of a sounds wave; pitch is a subjective percerption of that frequency.)
     
  4. Danger

    Danger 9,878
    Gold Member

    Also, the temperature will affect the physical properties of the instrument itself, such as string tension and reverberation.
     
  5. I would bet that thermal expansion (or contraction in this case) of the various materials in your instrument has a much more pronounced effect than the density of air. Secondarily, you may, in some cases, have material stiffen and/or embrittle as well, and that would also have an effect.

    If you really wanted to test this, I would say leave your instrument outside, then bring it into a warm room to play while cold. That should be pretty instructive.
     
  6. K^2

    K^2 2,470
    Science Advisor

    In wind instruments, the pitch depends on speed of sound, which depends on temperature of the air. In string instruments, on tension in the string, which can also depend on temperature if the thermal expansion/contraction coefficients aren't matched by these of the frame. For voice, the main factor is tension in the vocal chords. Gas properties do affect the pitch of voice, but the temperature changes won't make a big enough change that the person wouldn't correct for it with vocal chords.
     
  7. I knew that when i leave my guitar in like my car and then try to bring it inside to play it the tuning gets all screwy...

    So what things effect tension in your vocal chords...i know that like eating and drinking do, but is that it?
     
  8. DaveC426913

    DaveC426913 16,374
    Gold Member

    You know what happens when you inhale helium. Ever seen what happens with you inhale sulphur hexfluoride?
     
  9. Danger

    Danger 9,878
    Gold Member

    Unfortunately, I have been deprived of that opportunity. I ordered a balloon at Ducks last night, but the buggers were sold out. Maybe next week...
     
  10. I wouldn't suggest that. Rapid changes in humidity and temperature are generally not good for your instrument. But yes, the change in temp is what is causing your guitar to detune.
     
  11. DaveC426913

    DaveC426913 16,374
    Gold Member

    They had SF6 balloons at ducks?
     
  12. Vanadium 50

    Vanadium 50 18,050
    Staff Emeritus
    Science Advisor
    Education Advisor

    A lot of people think this, but it's not true. (Well, Danger's is true, but it's not the most important factor). The speed of sound in air changes by of order 10-3 per degree. The coefficient of thermal expansion is of order 10-5 per degree.
     
  13. Borek

    Staff: Mentor

    Hexafluoride.

    Note that while inhaling helium is safe - it is light so it will leave the lungs very fast - this is not the case with SF6. It is inert and not toxic, but it is heavy and tends to stay in the bottom of the lungs, blocking access of a fresh air.
     
    Last edited: Dec 6, 2010
  14. Rather than thermal expansion of the strings themselves (or a change in elasticity), what about thermal expansion of the tuning knobs? If the de-tuning of the guitar is permanent it has to be these, presumably if they contract even a little, with a good few cm of string wrapped around them it could lead to a noticeable alteration in pitch.

    If you have the guitar in the cold for a long time, then bring it to room temperature and play after an hour, and it's still not in tune, then I'd have a guess that it's the tuning knobs rather than any effect on the strings directly.
     
  15. ok thanks for the info.
     
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