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A Why don't bowed musical instruments deaden their sound?

  1. Sep 30, 2016 #1
    Horsehair is a string of tiny bead-shaped growths -- from what I have read. Even that slides over strings until rosin allows the "beads" to grab temporarily. But if one bead pulls and releases the string, wouldn't the other strings in the horsehair "hank" dampen that sound? It obviously doesn't but I don't get why. TIA.
     
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  3. Oct 1, 2016 #2

    Fervent Freyja

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    The vibrations are traveling along the string of the instrument to produce sounds in the bridge and body, not in the strings of the bow. If the hairs are too tight/loose or the bow has an excess of hairs, then sound quality will ultimately be affected (by preventing it from catching the string).
     
  4. Oct 1, 2016 #3
    Let us analyse the action of bowing in detail:

    As the bow drags across the string, the string is pulled slightly to the side, because static friction is greater than string tension.

    At the dragged point where the horizontal component of string tension becomes greater than static friction, the string returns to its original position and moves further the other way, because the string tension creates a harmonic motion;

    The bow slides across (sliding friction is smaller than tension)

    But instead of the harmonic motion dying out, at some point the horizontal component of tension will get small enough due to the decreasing amplitude of the harmonic motion and thus the sliding friction becomes greater; the string stops on the bow, and static friction takes over.


    The above cycle, repeated per bow movement, produces a complex musical wave pattern. And the bow (horsehairs with resin) does not deaden the sound produced.

    Moreover the player always varies the pressure of bow on the string such that the frictional forces are adjusted.

    for detail pictures pl.see
    <http://www.erhuphysics.net78.net/bowing.htm> [Broken]
     
    Last edited by a moderator: May 8, 2017
  5. Oct 1, 2016 #4
    i think the sound waves are produced in the strings which are being bowed
    and the box and the bridges do not 'originally' are producers of vibrations
    The bridges are used to vary the length of the string and Box is used as resonators for the sound being produced..
     
  6. Oct 1, 2016 #5

    Fervent Freyja

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    You don't say!
     
  7. Oct 1, 2016 #6

    olivermsun

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    The rosin also plays a big part in the stick/slip behavior described above. Under sliding friction the rosin melts and reduces friction. When the sliding stops the rosin "freezes" and sticks the hair and string together even more strongly. The pressure on the bow actually affects the torsion mode of the string and keeps the stick/slip phase locked with the traveling wave mode.
     
  8. Oct 1, 2016 #7
    I went to a violin shop today and the salesman demonstrated this with a "clean" bow over a violin string -- very little sound. Then, the same with rosin applied to the bow -- very rich sound. The string was vibrating in its complete 1st harmonic; that is, the bow was only contributing to vibrating the violin string and was not dampening the length of the string. The salesman bowed near the bridge, at mid-point, and over the fingerboard: same results. So I guess the answer that mentions one force in the horsehair being temporarily stronger that other forces in the horsehair makes sense (I think). Thanks to all. BTW, this question and the answers are in a tough concept to describe without diagrams.
     
  9. Oct 1, 2016 #8
    Last edited by a moderator: May 8, 2017
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