Test correlation

[Tphil]

Correlating test charts with visual observations can challenge my faculties at times so I put this together which doesn’t take much time and gives me an at-glance reference to some of the things going on in the instrument.
Not being a dyed-in-the-wool left brainer, it still takes some time to glean all that’s to be got from spectra but this gives me something to ponder and wonder why about.
The instrument is a Tenor uke – Toona all round. The spectrum was produce by tapping the bridge and the centre of the back lower bout. My tealeaves needed more excitation than my obviously puny setup provided but still gave me something to think about.
Any thoughts about what’s going on with the spectrum at 613 and 709 are welcome.

Trevor

[woodrat]

...Nice work Trevor....a great visual way of showing this...

Welcome to the Forum too..

John

[kiwigeo]

Any thoughts about what’s going on with the spectrum at 613 and 709 are welcome.

My first thought is that you've not correctly matched the Chaldni patterns to the spectrum analysis. Are you sure the patterns don't correspond to nearby peaks?

As an aside, something I've noticed on my classicals is that the Chaldni patterns are more strongly influenced by the bracing pattern at higher frequencies.

[Tphil]

My first thought is that you've not correctly matched the Chaldni patterns to the spectrum analysis. Are you sure the patterns don't correspond to nearby peaks?

I haven't really matched patterns to peaks, just marked for clarity where the frequencies noted on the pattern shots lie on the scale. The lower ones seem logical enough but the upper two remain a bit of a mystery.

[charangohabsburg]

When I do Chladni pattern tests I drive the top at exactly those frequency peaks of the FFT curve to see what I have there. I don't bother about the Chladni patterns between the prominent peaks - at least not yet.

[Tphil]

I took a more "I'll take what I can get" approach and swept the entire range looking for signs of disturbance. I did dwell longer on those major peak areas, sometimes not getting the expected result. My setup's a bit primitive - a handheld 60W 8" speaker with the box resting on Gladwrap stretched over a frame - no focusing tube. I stopped dialling in more power when the speaker started to stink.

[kiwigeo]

When I do Chladni pattern tests I drive the top at exactly those frequency peaks of the FFT curve to see what I have there. I don't bother about the Chladni patterns between the prominent peaks - at least not yet.

This is what I do.