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View Full Version : Helmholtz resonance values for ukes?



ichadwick
02-24-2009, 06:33 AM
Any luthiers here know the range of frequencies for the Helmholtz resonance in various uke sizes?

Does anyone here actually use the Helmholtz values when building a uke?

Pete Howlett
02-24-2009, 06:54 AM
No - there's no point. It applies to bowed instruments which work differently from others.

ichadwick
02-26-2009, 07:30 AM
No - there's no point. It applies to bowed instruments which work differently from others.

Well, it actually applies to any instrument that has an enclosed body cavity. There's quite a body of work on the building of and physics of guitars in relation to the Helmholtz resonance factor. It's quite noticeable in a guitar - simply slide a piece of paper over the sound hole whole playing the low notes and you'll hear the difference. I can hear it on my ukes, albeit considerably less so than on my guitar.

Stackabones
02-26-2009, 07:31 AM
Interesting! I don't have an answer, but I stay tuned in.

koalohapaul
02-26-2009, 06:15 PM
The actual frequency differs between body size and sound hole position, geometry, and size. Most ukulele are somewhere between F and G.

Moore Bettah Ukuleles
02-27-2009, 07:06 AM
Helmholtz resonance can be demonstrated by blowing air across the mouth of a bottle to create a tone. Same thing can be done with an air compressor blowing a stream of air across the sound hole of an uke. (I discovered this by accident while blowing debris out of the sound box.) My tenors tend to resonate at G.
You're welcome for this useless tidbit of information!

Stackabones
02-27-2009, 07:08 AM
My tenors tend to resonate at G.


Does that mean that your tenors sound better in the key of G? Or in songs that have a G chord (key of C or F or etc) or a G note in them?

Moore Bettah Ukuleles
02-27-2009, 07:31 AM
Helmholtz resonance is affected primarily by the volume of the sounbox and the size of the sound hole. My tenor design has remained the same for many years and I have not experimenting with these variables.

koalohapaul
02-27-2009, 07:36 PM
Ha ha! Chuck, your comment about the air compressor made me chuckle. Sometimes we do the same thing across the shop, but not to check the Hemholtz resonance. Basically, we're just screwing around and start making calls to each other using the air gun and uke bodies.

Bradford
03-04-2009, 05:29 PM
I just picked up the Peterson Strobosoft software a couple of weeks ago. The body resonance of a mahogany soprano just being finished is D4, -19 cents. To answer a question in the thread, if the resonance of an instrument lands exactly on a note, that note or chord is going to sound much louder than others. It is my understanding that you want to be somewhat sharp or flat from any semitone.

Brad