• Question: How does a violin work? Is it to do with friction?

    Asked by #nerdyweirdo to Chris, Josh, Rebecca, Rob, Susan on 18 Jun 2015.
    • Photo: Rebecca Dewey

      Rebecca Dewey answered on 18 Jun 2015:

      A little bit. It’s also a lot to do with vibrations and harmonics.

      The bow of the violin is used to rub a string, and the friction between the two causes the string to vibrate. Once the bow has been removed from the string, it will carry on vibrating. The vibration will spread throughout the entire length of that one string, from one end to the other, and the note produced will depend on the length of the string. This vibrating causes the air molecules surrounding the string to vibrate as well, and this is the source of the sound. This sound would usually dissipate quite quickly away from the violin string if there is nothing to keep the air molecules in place to build up more concentrated vibrations, so the hollow wooden body collects some of the vibrating air and allows it to resonate, making the sound loud enough to be audible several metres away.

    • Photo: Susan Cartwright

      Susan Cartwright answered on 18 Jun 2015:

      Yes, but more to do with waves and vibrations.

      Sound is a wave that travels in the air – it’s alternating higher and lower densities. The violin causes the sound wave by vibrating, pushing the air molecules rhythmically to produce the sound wave. The vibration is caused by the violin strings, but amplified by the violin’s hollow body (electric violins, which use electronics to amplify the sound, are often little more than a support for the strings). The thickness of and tension in the strings affect the frequency at which they vibrate, which is why each string of the violin gives out a different note.

      Friction comes into play when you consider the bow. You set the strings of the violin vibrating by drawing the bow across them, and it’s the friction between the bow and the strings that makes that happen: essentially, the string sticks to the bow a little bit, and is therefore pulled sideways – when the stretching gets too much, it pulls off the bow and springs backward, but overshoots – this gets it vibrating. If the bow were frictionless, the string would not stick to it, and there would be no sound. (This is why you put rosin on the bow, to enhance the friction.)

      Other stringed instruments induce the vibration of the strings in different ways. In a guitar, you pluck the strings; in a piano, you hit them with a hammer.

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