I saw an episode of Discovery channel's show Time Warp where they filmed someone pulling the bow across two open strings-it was a quick stroke, only about 2 seconds, but they captured it with a super highspeed camera. The result was a super slow motion video clip that allows you to examine what happens when in those two seconds are stretched over a minute. Here's the link to the video. Unfortunately, I haven't found a clip of it in real-time so you can hear and see the original.
The slow motion allows us to actually see the physics of the classical ratio of a perfect fifth. If you count the vibration cycles of the two strings, you'll notice that in the time it takes for the D string to vibrate twice, the A string vibrates three times. To do this, I set the video at the 0:20 mark and counted the "grab and release" cycles of the D string until I counted 10 cycles - the video was now at 0:27. Next, I counted the cycles of the A string from 0:20 to 0:27 = 15 cycles. This indicates that the violin was in tune as the 3:2 ratio in the movement of the strings vibration reflects the ratio a perfect fifth (A = 440 Hz D = 294 Hz, 440 / 294 = 1.5).
While doing this, I noticed that the "grab and release" action of the bow hair on the strings was not perfectly consistent. Sometimes there wasn't a steady pulse in the vibration of the D or A strings. I'm thinking that perhaps the bow was not equally on the two strings. Also, I'm wondering if this video illustrates what happens when the bow pressure and speed and distance from the bridge are not in the optimum balance (i.e., the sound point). Even though the elapsed time is only a couple seconds, a number of things happen that introduces inconsistency and I'm thinking that these abberations create noise that detracts from the purity of the tone. My theory is that when a violinist plays a note with good tone - the sound point is achieved, that the physics of the string motion under the bow would be perfectly consistent (or nearly so). Some of the inconsistencies I noticed in the video were:
I'm wondering what others notice from this clip. Do you think there is any merit to the theory that the noise/abberations we see are a hinderance to producing a pure tone?
From what I remember from watching the original episode several months ago, the real-time duration of this clip is about 2 seconds and the woman playing the violin casually pulled the bow across the strings (i.e., there was no apparent attempt to produce a high quality sound). It would be very interesting if this clip were duplicated wtih a violinist who could instantly hit the sound point.
FYI: HowStuffWorks wrote up a description of this video that outlined some of the basic physics involved.
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