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Different subsidiary notes with varying amplitudes

  1. Jun 5, 2007 #1
    1. The problem statement, all variables and given/known data

    1. Two identical guitars are played by two persons to give notes of the same pitch. Will they differ in quality? Give a reason.

    2. How do you account for the fact that 2 string instruments can be used to give notes of the same pitch and loudness but different quality?



    3. The attempt at a solution

    I thin the answer for both questions is that they have different subsidiary notes with varying amplitudes. They have different wave forms. Isnt it?
     
  2. jcsd
  3. Jun 5, 2007 #2

    Andrew Mason

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    What factor determines the quality of the sound produced by the vibrating string?

    What is it about plucking a guitar string that determines which of these frequencies are exited and in what proportion? Think of the shape of the string just before it is released and think of fourier analysis of that shape.

    AM
     
  4. Jun 6, 2007 #3
    I have already trold that in my answer.
    I dont think much detail is there in our course about it. Will youlease help me with a simpler answer?
     
  5. Jun 7, 2007 #4

    Andrew Mason

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    I am not sure what you mean by subsidiary tones. Quality is determined by harmonics (or overtones, or harmonic frequencies). The quality of the sound depends on the number and respective amplitudes of the higher harmonic frequencies.

    The difference in plucking of the string - the difference in the shape of the string just before letting it go - leads to different harmonics (quality). If the string is plucked near the middle of the string, it will excite different frequencies than if plucked nearer one end. Also, if it is plucked with a soft finger, it sounds different than if plucked with a pick - because the different plucking techniques create different shapes (hence different harmonics). This is easy to show using Fourier analysis.

    AM
     
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