Quote:
Originally Posted by Otterhound
A result of playing my recent 12 Fret 0 build , I noticed that there is a nodal/harmonic dead on the middle of the sound hole .
This seems to have created the effect of exciting unfretted strings to produce sympathetic harmonic resonances/tones .
I find this to be a pleasing chime during play .
Am I correct in my assessment of this phenomenon ?
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Hmmm...
Firstly, the node in the middle of the soundhole is probably the 4th harmonic, as rick says, seeing as the centre of the soundhole is (in most acoustics) roughly half-way between bridge and 12th fret. The 4th harmonic node is at 1/4 string length, and produces 2 octaves above the open string. (Compare it with the 5th fret harmonic.)
Secondly, I don't understand what you mean by "created the effect of exciting unfretted strings to produce sympathetic harmonic resonances/tones". Harmonic nodes don't "create" such things (regardless of position). Unless perhaps you actually
play the harmonic, maybe...
What makes unfretted strings vibrate in sympathy is fretted notes (or harmonics) that either have the same frequency as the unfretted strings, or share lower harmonics.
E.g., if you were to play that soundhole harmonic on your 6th string (if it is the 4th harmonic), then the first string would vibrate in sympathy, because it's the same pitch. You might also get sympathetic resonance from the A string, because its 3rd harmonic is the same pitch (near enough). You'd get the same effect from the 5th fret harmonic (on 6th string).
"Pleasing chimes" while you play may be due to all kinds of sympathetic resonances (from unfretted strings) depending on what notes you're playing, and is nothing to do with the position of a node relative to the soundhole or any other position. Harmonics are all about string fractions, as rick says. The nodes for fretted strings are of course in different positions from those for open strings.