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B Quality of Sound

  1. Apr 5, 2016 #1
    For the quality, or timbre, of sound, multiple harmonics are present. How is that possible for a string or a tube? Are there any good pictures of how a wave on a string has multiple harmonics present at the same time? Thanks.
     
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  3. Apr 5, 2016 #2

    DrClaude

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    The number of harmonics present will depend on how the sound is generated. If you pluck a string, it is very difficult to do it in such a way that only the fundamental is vibrating.
     
  4. Apr 5, 2016 #3

    collinsmark

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    Not only is it possible, sometimes, on some instruments, the higher harmonics are dominant.

    Here is a song, Roundabout, by Yes. In the introduction the guitarists isolates various harmonics on the strings by placing a finger of his fretting hand at certain "nodes," thus isolating the desired harmonics (That's not done for the entire introduction, but it is done about 5 times or so, sometimes with multiple strings at once.) He's not actually fretting the strings, he is merely strumming open strings open while briefly touching the strings at certain locations to isolate the particular harmonics. These harmonics would normally be there anyway, but what he's effectively done is removed all or most of the other harmonics, including the fundamental of each string.



    Here is a video that plays various sounds and lets you "see" the waveform using an oscilloscope.

     
  5. Apr 5, 2016 #4

    sophiecentaur

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    For many musical instruments, the 'harmonics' you refer to are far from harmonically related to the fundamental note. Strings are pretty well behaved because they are well clamped at each end but many wind instruments are far from perfect. The high components of notes are referred to as Overtones and these overtones strongly define the timbre of an instrument. Early synthesisers were based on mixtures of harmonics and had their own characteristic sounds. Interesting and pleasant sounds but nothing like the 'Instrument' labels that were on the tabs. The synthesisers which use samples will sound more 'real' but they mostly vary the pitch by altering the replay speed of a single note. This, again, is not realistic because the different registers of most instruments have a different timbre.
    So the geometrical shapes that appear in the movies (above) would not appear on the waveforms from real instruments. Even the waveforms from a guitar string do not have regular patterns and the higher spectral components (approximate harmonics) run through the trace, never producing a well behaved and long lasting wave shape.
     
  6. Apr 5, 2016 #5
    What does quality sound mean?

    Sounds subjective?
     
  7. Apr 5, 2016 #6

    sophiecentaur

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    When you hear it, it is subjective.
    I interpreted the word "quality" as "characteristics" - which are measurable.
     
  8. Apr 5, 2016 #7
    Assuming pure tones are high quality??
     
  9. Apr 5, 2016 #8

    sophiecentaur

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    That wouldn't be a 'musical' high quality. It could indicate a reasonable 'quality' of amplifier or recording, with a sine wave input.
    A good violin will produce a very 'impure' spectrum and so will a rubbish violin.
     
  10. Apr 5, 2016 #9
    So then what exactly are we discussing??
     
  11. Apr 5, 2016 #10

    sophiecentaur

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    Timbre? That's only got one meaning and it's in the OP.
     
  12. Apr 5, 2016 #11

    DrClaude

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  13. Apr 5, 2016 #12
    K, I have not read up on the musical aspects of sound so not familiar with this term, what's the difference between good quality/timbre and bad quality/timbre and what units is it measured in.
     
  14. Apr 5, 2016 #13

    DrClaude

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    It is not "good" or "bad." It is what allows you to differentiate between a guitar, a piano, and a human voice playing the same note.
     
  15. Apr 5, 2016 #14
    Well quality is kind of a misleading word. Its really a spectrogram?
     
  16. Apr 5, 2016 #15

    sophiecentaur

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    No units - except £ and $, afaik. It's in the same street as art and taste - there is usually some agreement between experts about really good and really bad but it's too subjective to quantify.
    But the OP is asking a much more basic question and that is about the frequency analysis of sounds from strings. I would have expected anyone who wanted pictures of that would try googling first and find something to suit their particular level of enquiry. I could suggest A google search with key words like: Frequency spectrum of string vibrations.
     
  17. Apr 6, 2016 #16

    Svein

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  18. Apr 6, 2016 #17

    jtbell

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    So are a lot of "common words" when used in certain specific fields. Consider "color" and quarks, for example. o0)
     
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