I play guitar, and know a little bit about the physics of how it works. I know that the frequency of the note produced increases as the string tension gets higher, as the string diameter gets thinner, and as the string length gets shorter. Is it possible to make a string that is thin enough, tight enough, and short enough to produce a note that is above the range of human hearing?
In theory yes. But the highest note on a guitar with the usual tuning is around 1100 hz I think. That makes the guitar range about 4 octaves, about 70-1100 hz. Human hearing is often said to be 20-20000hz (another four octaves higher), although I’ve lost most of the top of that–give me a few years and I won’t be able to hear some notes on this guitar.
http://www.radioyur.com/les10.html
http://hypertextbook.com/facts/2003/DanielleDaly.shtml
Well, the highest note on a standard piano is C7, which is about 4 kHz. And that’s a tiny string (actually three strings).
Depends. Could God himself make a guitar note so high that he himself could not hear it?
It is possible to hit a “harmonic” on a guitar. All you do is put your finger over some place on the string where you will hit a standing wave and pluck the string. An easy one is the halfway point of the string, but you can find them all the way up and down the string (for example, 1/4 the length of the string, 1/8th, etc). They get a little harder to hit the further you go up the string, but not impossible. Theoretically you could hit one that is above the human range of hearing, but I don’t know how you would know if you successfully hit it or not unless you had the guitar hooked up to an oscilloscope or something.
An easier way is to press the string down in the 12th fret, and play it. 