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B How to record the frequency of a string using a phone

  1. Apr 27, 2016 #1
    I am currently conducting an experiment where I attach a string to a fixed end and run the other end over a pulley (assuming zero friction). A weight is tied to the end to create tension. We currently have length, mass per unit -length and tension, the only issue is measuring the frequency of the string. Is there any way to use a phone or other simple means to record or measure this?
  2. jcsd
  3. Apr 27, 2016 #2
  4. Apr 27, 2016 #3
    The only issue is that there is nothing for the sound to resonate against meaning the string does not create an audible frequency.
  5. Apr 27, 2016 #4


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    Well the strings energy is going somewhere. In a loud backstage area, too loud to tune an unplugged electric guitar by ear, you can bite down on a guitar headstock and hear enough to tune up. Vibrations are transferred directly to your ear drums. The modern equivalent is to touch your cell phone to your guitar and use a tuner app (or use a contact tuner). If that doesn't work a contact transducer can be used, sandwich it wherever vibrations are transmitted, coin piezo's are just a few cents each.
  6. Apr 27, 2016 #5
    Something must be vibrating. Buy a cheap suction cup microphone and attach it.
  7. Apr 28, 2016 #6
    Use guitar strings and a guitar pick up attached to a CRO.
  8. Apr 28, 2016 #7


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    Regular electric guitar pick up affect the pitch of the string, it's inherent to their operation, the string must be in the magnetic field and so it's tension is increased. Not a problem for music as it's normally below the human pitch perception threshold (or is swamped by other factors) but may be a problem for a science experiment.
  9. Apr 28, 2016 #8
  10. Apr 28, 2016 #9

    Andy Resnick

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    Does the string vibrate within the audio range (say 100 Hz - 10 kHz)?
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