The note of your guitar

[ljguitar]

Hi all

Some of you are mixing up sympathetic vibration (sing and A into the sound hole and the A string sympathetically vibrates) with Helmholtz Resonance or the natural resonance pitch/frequency the body of an acoustic guitar produces.

For sympathetic notes to manifest, the strings must be free to vibrate. And then when you match the pitch (even when it's tuned improperly) the string will vibrate sympathetically at that pitch.

A Helmholz Resonance will manifest with all the strings muted. It's often around a low G (G2 on the 6th string tuned to E), and it is far louder than sympathetic vibrations. The entire body will sound quite loudly when the pitch producer matches the actual frequency.

It's related to the sound one produces blowing across an empty bottle (or one with liquid in it).

It's pretty hard for women to produce it by singing, because it's in the low baritone or bass range for men.

Tested it using Airyware Tuner with iPhone laying on the top of each guitar adjacent to the sound hole while I held the guitar in my hands, muted the strings, and sang gently into the sound hole…I slowly dropped my voice in pitch till I arrived at the Helmholz note (singing an open AHH). I had my Airyware tune tuner app running, and pulled 6 or 8 samples and averaged results/readings (all within 2 cents of each other).

Olson Dreadnought - 93.68Hz - (Gb2 +4 cents)
Kronbauer Mini Jumbo - 104.5Hz (Ab2 +11 cents) - this guitar has a side port added after the guitar was built.
Bashkin OM - 98.76Hz - (G2 +4 cents)

These were quick and dirty measurements.

Again, this has nothing to do with strings.
It is the natural resonant frequency of the box (the lowest one I believe). Since I cannot sing a fifth or octave lower I have no way to prove that absolutely, but the readings line up with discussions Alan Curruth - luthier and member here - has posted on the topic.

It'd be good if Alan wades into the discussion and sets me straight. It's not in the same category as sound-hole-sniffing.

[Peter Z]

Thank you mc1 and Ijguitar.

1) dampen the strings, they shouldn't vibrate —- edit: sorry, I meant ‚mute‘ the strings!!!
2) hum a low frequency sweep from E to maybe A into the soundhole and listen to what comes back

You will immediatly know why some people hum into their guitar. I never put my nose into my guitars and sniff. But knowing the helmholtz frequency isn't a bad thing.

[musicman1951]

You are all avoiding the real question: what kind of construction/destruction do I do to my instruments to change the note to one I like better?

[redir]

Originally Posted by musicman1951

You are all avoiding the real question: what kind of construction/destruction do I do to my instruments to change the note to one I like better?

The easiest thing to do would be to add or subtract mass from the top. A wolf note is the note that equals the body resonant frequency and cause's a problem. So for example if your body freq is right exactly on A then when you play an A on a very resonant guitar it will act in a less then desirable way. Since it is the same as the body freq then the energy of the string will be used to amplify the body and as such it will be an extra loud note for a very short duration.

To treat wolf notes you can take some blue tack putty and stick to the guitar in various places usually around or on the bridge. Once you kill the wolf you weigh the blue tack then cut a piece of spruce the same gram weight and glue it to the top on the inside.

Another way to change the resonant freq is to change the size of the sound hole, add mass to the sides, and in some cases shave down some back braces.

[ljguitar]

Originally Posted by musicman1951

You are all avoiding the real question: what kind of construction/destruction do I do to my instruments to change the note to one I like better?

Hey m-man

Increase/decrease size of soundhole.

I never tested the Kronbauer's frequency before I had the side port added, but I think that affected the frequency a tiny bit.

[Peter Z]

Larry is right again. The Helmholtz frequency is depending on the size of the (sound)hole and on the size of the body.

But you have to consider there is not just the Helmholtz frequency, there are also resonances of the top, back, sides and neck of the guitar. And of course the strings. All those frequencies depend on the shape and the mass of the parts and add up in a quite complicate way.

Thus, a wolf note is not only depending on just one thing.

[Alan Carruth]

There's another thread about this, 'Top Frequency', and I just responded to MartinGibsonFan's objection in that thread.

[ljguitar]

Originally Posted by Alan Carruth

There's another thread about this, 'Top Frequency', and I just responded to MartinGibsonFan's objection in that thread.

Hi Alan
I read your responses (thorough and clear as usual) in the other thread. Thanks for taking time to post info like this.

I wish people were not so dismissive about topics, and would try to discern what people are asking instead of just making light and non-related remarks.

Enough complaining…thanks again for posting those answers in the 'Top Frequency' thread.

[KarenB]

Perhaps humming to the soundhole will help guitars break-in faster. And since I can't sing live with people right now, doing singing to and with my guitar might be a good substitute. The guitar could be the drone and I'd hum wherever inspiration takes me.

[MartinGibsonFan]

Originally Posted by ljguitar

Hi Alan
I read your responses (thorough and clear as usual) in the other thread. Thanks for taking time to post info like this.

I wish people were not so dismissive about topics, and would try to discern what people are asking instead of just making light and non-related remarks.

Enough complaining…thanks again for posting those answers in the 'Top Frequency' thread.

After discerning, I noticed different notes coming out of the box, depending on the input, so I guess I can be admonished.

It's an interesting observation, but that's pretty much it.

J

[mercy]

Thanks to all who participated

[nickv6]

Had the OP said "hum with the strings muted" I might well have been able to discern a bit more.....
I must try adding random words to posts to see what else I can discern that isn't said.
Nick

[Rixtoy]

OMG - my wife already is most curious/suspicious about what goes on behind the closed doors of my music room.

If she walked in and found me with my mouth on the sound hole humming into the guitar, I just don't know what the ramifications might be . . .

Jus' sayin' . . .

[nickv6]

Originally Posted by Rixtoy

OMG - my wife already is most curious/suspicious about what goes on behind the closed doors of my music room.

If she walked in and found me with my mouth on the sound hole humming into the guitar, I just don't know what the ramifications might be . . .

Jus' sayin' . . .

Better your mouth than.......

[Peter Z]

Better your mouth on the sound hole than ...