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McBruce
05-17-2011, 06:35 AM
I was wondering if anyone worried much about the resonant frequency of their Ukulele? There's a lot of data supporting head tension and resonant cavity affecting overall tone in Banjos, but I haven't seen much in the Ukulele world. Just for fun, I checked and my Luna Concert resonates at a near perfect E. The easy way to check this is to sing a low note in the sound hole with a tuner attached and then ramp up the frequency until it starts to really resonate. For me, it would be interesting to compare the resonance of 2 identical Ukuleles that had exceptional and average tone.
It would be interesting to see what the resonant frequency is of other Ukuleles to see if it makes a difference in tone or volume. For me, it would be interesting to compare the resonance of 2 identical Ukuleles that had exceptional and average tone. I had considered putting something in the cavity to try to change the frequency to see if that had an effect, but haven't made the time to do so.
Anyway, just wondering if anyone else had any data on this.
Thanks,
Bruce

Doc_J
05-17-2011, 07:22 AM
In simple vibration theory if we assume the string is the "forced" input, at a resonant frequency of the soundboard, the forced component of the output (displacement of the sound board) should be of larger magnitude. Larger vibrations of the sound board should produce larger sound volume, at and near the resonant frequency. But soundboards are not simple oscillators with only 1 natural frequency. Plus there are a whole lot of other issues (damping, phase, beating, etc.). Not too long ago I modeled a simple soprano soundboard, and found a natural frequency near the A-string frequency (440 Hz). This was a second or third mode, above the first natural frequency. It helped me understand why I thought the A- string sounded different, after the sound board was severely sanded on the A-string side.

Just my 2 cents.

Bradford
05-17-2011, 07:26 AM
I use Strobosoft tap tuning capability to check the body resonance of my ukes. I use my finger to tap the bridge, the software averages three taps and displays the results. What I have seen, not surprisingly, is over the years as my ukes have improved, this tone has dropped. My sopranos started out at C#4 -30 cents, they are now running B3 -15 cents. With this drop in body resonance, they are louder, richer with more sustain.

Brad

mzuch
05-17-2011, 09:24 AM
What I have seen, not surprisingly, is over the years as my ukes have improved, this tone has dropped.

Brad: What, if I may ask, were the practical steps you took to achieve lower body resonance and the associated improvement in volume, tone and sustain? Thinner plates? Larger sound chamber? Different soundhole size? Also, are you referring to flattop or archtop ukes?

Bradford
05-17-2011, 12:07 PM
I was referring to my flattop ukes. I attribute most of this to building lighter and stronger. Adding a radius to the top and backs allows you thin them a bit more, and make the braces smaller, over time you develope a feel for how light you can go. For the most part I use an intuitive approach to building, tapping and flexing the wood as I work it until it seems right to me. By measuring the body resonance, I get a least one piece of hard data.

Brad