acoustical illusion?

[edeltorus]

Few minutes ago I was listening to single notes. Fully focused, concentrated and with closed eyes. (notes on the g-string didn't ring out properly, and I wanted to know what it is...)

 

While I listend to the notes I noticed a high pitched sound. It was very aparent, but disapeared as soon as the note was stopped (at least I thought so).

 

I was absolutely sure that the high pitched sound was harmonically related to the note I played. Lots of octaves above, but related. A fifth or forth maybe.

 

So I recorded the note, did a frequency analysis and found out that it was just the pal tv row frequency (somewhere at 15Khz). Turning off the TV got rid of the high pitched sound (no surprise).

 

 

But now I ask myself:

 

Is it normal / an acoustical illusion that such high frequencies sound like a natural harmonic of a much lower note?

[Poparad]

When the fundamental note vibrates (any open or fretted note) all the overtones ring also at the same time (the harmonics). The volume of the fundamental is usually loud enough that you don't notice the overtones, but they're there. Sometimes, due to fretbuzz or an odd nut or bridge, the fundamental is dampened a bit, and you can hear the overtones much stronger.

[Poparad]

Originally posted by jdwinger I doubt that's the phenomenon here b/c turning off the teleivision killed the 'harmonic'

 

 

 

I did misread the original post, but that is still the same thing. I mentioned the fundamental being dampened, but here, the harmonic is being excited by another source. The frequency at which the TV hums happens to be an overtone of one of his strings.

 

 

It's similar to an experiment you can do with a paino: hold down a key on the piano without sounding it, and then play a note a fifth above or an octave above (the lower harmonics), and those notes will continue to ring after you release them, while still holding down that first key. That's similar to what's happening here; a note is exciting a certain harmonic on that string, albeit a very high one, but still one existing on that string.

 

 

 

Although, now that I think about it, was an electric guitar or an acoustic guitar? It could have been that the TV's magnetic waves were being picked up by either the guitar pickups or the amp. I know with my amp, if I place it on the floor where there's a power line running underneath it, I will get a loud hum picked up from the magnetic feild. As such, I have to keep my amp on a chair to keep it quiet.

[Factor]

Just a little something something:

http://www.exploratorium.edu/exhibits/highest_note/ex.about.fr.html