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Electrostatic/electromagnetic noise and conductive area

  1. Feb 8, 2017 #1
    I play electric guitar, and electromagnetic noise is a big concern for us.

    There are two types of noise, those that arrive as magnetic fields and those that arrive as electrical fields. This web page is a resource from which I've derived this understanding http://members.ozemail.com.au/~tabbler/GndRule/GndM02.html and it says that the source of noise and the circuit of subject (the electric guitar) can be thought of as two plates in a huge capacitor. The guitar and the source of the noise are on the same electrical circuit, so they guitar, and the wiring in the house capacitively couple, so the noise source capacitively inflicts a voltage upon the guitar, thus creating audible noise.

    My first question is, is the above interpretation correct?

    My second question is... guitarists know, and rely upon, the fact that touching the guitar strings and becoming a part of the "ground" side of the circuit greatly reduces noise. Is the reason that touching the string, and becoming part of the "ground" conductive area, reduces the noise because you are essentially making your side of this capacitor much larger, and by making that "capacitive plate" very large, you give the source of noise something to capacitively couple with other than the guitar's wiring on the "hot" side of the circuit?

    The inverse seems to be true also: if you somehow touch the positive side of the guitar's wiring (like when you're fiddling with the electronics) , the noise suddenly becomes louder. It seems to me that once again you are making the capacitive plate that is you and the guitar, much larger, but now you are imposing the additional voltage on the "hot" or un-shielded side of the circuit, thereby making it louder.

    Am I understanding what is happening correctly?
  2. jcsd
  3. Feb 8, 2017 #2


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    Science Advisor

    As a beginner you are on the right path. But it is a generalisation of an over simplified system.

    All energy travels as electromagnetic waves, that is, as an intimately coupled electric and magnetic field. For a simple analysis you can ignore one of them. The mode of analysis you select can be electric or magnetic, you will probably decide which to use based on the type of “pick-up” or “antenna” that is being influenced.
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