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Temperature and Pitch question

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  1. Apr 12, 2015 #1
    So I've been researching into this a lot lately as I want to learn just exactly what pitch is coming from my speakers but I'm getting confused. If pitch changes with temperature/speed of sound and 1hz is always the speed of sound. Then when using a midi instrument or electronical instrument.. how do you really know what frequency is coming from the speakers? Would tuning to say.. 256 hertz actually give you a 256hz tone from the speaker it comes out of? I want to know the exact frequency of the pitch coming from the speaker.. I just can't seem to find any info I can make sense of! I found a useful converter for working out the change in pitch depending on temperature but my problem now is.. where does it start? I mean how would I know what pitch to convert from.
     
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  3. Apr 12, 2015 #2

    Vanadium 50

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    The pitch coming from your speakers is independent of the speed of sound. It's whatever pitch was recorded.
     
  4. Apr 12, 2015 #3
    The speed changes in different media (like about 340 m/s in air IIRC) but frequency does not. So 256 Hz gives 256 Hz.
     
  5. Apr 12, 2015 #4
    Pitch won't change with temperature/speed of sound. The wavelength changes, but the frequency, which gives you the pitch, should not change. Analogue instruments are sensitive to temperature, but digital systems like midi instruments should not be, because they run on internal clock which has low temperature sensitivity.

    You can check the tuning using a digital tuner, like one guitar players use. But it should be spot on for a midi instrument.
     
  6. Apr 12, 2015 #5
    Thanks everyone. I think I'm getting confused by assuming the same rules apply as air columns. That has cleared up a lot for me.. I do have 1 more question if thats ok. Would I still use temperature for calculating wavelength? The actual sound travelling through the room. Would the wavelength coming from computer instruments be calculated by using the frequency from the instrument and room temperature? Sorry if this is really simple.. I'm basically learning this by reading it up online.
     
  7. Apr 12, 2015 #6
  8. Apr 12, 2015 #7
    I have been using a wavelength calculator and I think I do get the speed of sound part.. from that I figured that 1hz is always the speed of sound?
    I want to program reverbs to the exact properties of the note they are used on so that the reverb matches up with the wavespeed and wavelength, and also time them to the speed of sound.. a little musical experiment I have going on.
    So to do this would I just take the frequency of the note and the temperature of the room and use that formula? or a wavelength calculator?
    Just want to make sure I'm understanding. Thanks for helping me out here!
     
  9. Apr 12, 2015 #8
    I think that calculator was set to 1 kHz for default. Do the first one you said.
     
  10. Apr 12, 2015 #9

    SteamKing

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    hertz (Hz) is the unit of frequency. 1 Hz = 1 cycle per second. It's not a measure of the speed of the signal. That must be determined by other means.

    http://en.wikipedia.org/wiki/Hertz
     
  11. Apr 12, 2015 #10
    Thanks for replying but I do realise that hertz is the number of cycles and not the speed, what I really didn't grasp is how 1hz can have a wavelength of the speed of sound even if the temperature changes as I'd read that frequency changes with temperature but that seems to only apply to air columns. And also how the pitch of could still be 256hz from computer to ear after going through air. I could have asked the question a little better I guess. After reading through the replies and thinking on it a little.. I think I understand.. its that the wavelength changes but the pitch is constant so the wavelength of a 1hz tone is different depending on temperature. So the wavelength of a 1hz tone travels the 343m at 20 degrees every second? And will always travel at the speed of sound meaning the distance in a second.
    So If I were to time a 256 hertz tone to the speed of sound that would be 120bpm right? and to do it with say.. 260 hertz id just do 260/256 x 120?

    So if I want to time a reverb effect with relation to the speed of sound for say a perfect fifth I could use 256 x 3/2 and then use the wavespeed/wavelength by using a wavelength calculator and the temperature of the room for 384hz for settings on the reverb.. hopefully this is not crazy talk!
    Please correct me if I'm still wrong or if I'm missing something still aha. really appreciate the replies here.. ive been trying to fully grasp this for a while now.
     
    Last edited: Apr 12, 2015
  12. Apr 12, 2015 #11

    SteamKing

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    You're getting wave concepts muddled together.

    Read this article which discusses the relationship between wave speed, frequency, cycles, etc.:

    http://hyperphysics.phy-astr.gsu.edu/hbase/wavrel.html#c1

    For a given wave speed, there may be one cycle or many cycles which occur each second. How many cycles which occur each second determines the wavelength, given the speed of the wave. Thus, a 1 Hz sound wave has a very long wavelength, while in a 256 Hz sound wave, the wavelengths are only 1/256 as long.

    A "beat" has a specific meaning in wave physics; it's the phenomenon we perceive when two or more sound waves of different frequencies arrive simultaneously at our ears. The periodic interference of the waves with one another produces an effect in which the volume of the sound increases and diminishes:

    http://en.wikipedia.org/wiki/Beat_(acoustics)
     
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