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Decibel & voltage formula

  1. May 12, 2008 #1
    Hey im writing an experiment which has a speaker connected to a power supply playing a continuous note. a decibel reader reads the volume from 0v to 12v. i know that as the voltage goes up so does the decibels but what theorem can i use to compare this with the results that will be recieved? thanks:smile:
  2. jcsd
  3. May 12, 2008 #2
    To convert voltage into decibels:
    [tex]G_{\mathrm{dB}}=20\log V[/tex]

    Where [tex]G_{\mathrm{dB}}[/tex] is the value in decibels and V is the voltage measured in volts.

    Thats log base 10 by the way :tongue:
  4. May 12, 2008 #3
    How would i use this? i am really confused atm lol :confused:

    does it depend on the speaker size or not.
  5. May 12, 2008 #4
    Ok, start slowly.

    What are you trying to measure?

    My understanding is that you are playing a pure tone from a signal generator into a speaker. Then what?

    I thought that the 0v to 12v was a voltage out across the speaker terminals that you wanted to convert to decibels.
  6. May 12, 2008 #5
    A db to watt per speaker might be better.
  7. May 12, 2008 #6
    then by a decibel reader i read the decibels from the speaker and and turn the voltage up and record the decibels again.
  8. May 12, 2008 #7
    Ok, so the decibels are from the sound and you want to find out the amplitude of the sound as a function of the amplitude of the voltage put into the speaker.

    Is that right?

    If it is:
    [tex]A=10^{\frac{G_{dB}}{20}}[/tex] will give you the amplitude of the sound. The amplitude of the voltage is a known quantity then since you are putting that into your speaker.
    Last edited: May 12, 2008
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