Brand new Gibson Hummingbird with Wolf tones

[Mark Funk/ funk guitars usa]

It bothers me Gibson would even let that happen considering the money they charge for thier guitars!

[Michael Minton]

Hmmm.

F2 is actually 87.31 Hz, so you wouldn’t be finding that on the A or D strings (unless it was somehow producing a half harmonic).

Maybe you meant F3? But F3 is 174.61 Hz. Closer to the main body resonance would be E3 at 164.81. But if the E isn’t a wolf note, F being a wolf note isn’t making sense to me based on the resonance, because the resonance is a full tone away from F.

[Neil Miller]

Thanks for the correction. My recollection is that the tone came at F3, but you’re right, that’s a half step away from the top resonance. All the other evidence fit so well that I misread my frequency chart.

Can you think of any other explanation for why an atypical buzz would occur at the same frequency on 2 strings, and go away completely when the top plate is damped??

If I still had the guitar, I would want to recheck my frequency analysis…

[Paul M]

that peak looks a little “wolfy” in how it breaks.

I don’t think any manufacturer warranties against wolf tones, that would be kinda nuts.

You could try putting a small amount of fun tack (or a large amount) somewhere near the bridge area and see if that moves the wolf between two pitches (make sure the guitar is at 440 before you do). If that works, you could weigh the fun tack and make an equivalent weight piece of wood and glue it inside the guitar at the same location.

You could also tune the guitar to a slightly lower pitch (maybe 438) and see if the wolf disappears or moves.

Not sure. You could ask Guiliano….

[Scott Liebers]

Any chance you have a recording of the buzz, or wolf note? I don’t have any insight to offer. I’m curious what you and your customer are hearing. I recently worked on a guitar with reported fret buzz on only a few notes on the high E string. It wasn’t a typical fret buzz sound however, I would describe it as an extra resonance. Further investigation revealed a worn saddle where the string had cut into the bone slightly and made an uneven ramp. There were only about 4 notes spread along the string length that produced this noise.

[Michael Minton]

I am getting way above my pay grade here, but if you accept that

(1) a wolf tone occurs when the impedance mismatch between string and soundboard is minimized and a resonance is created (allowing vibration at that frequency to be rapidly and efficiently admitted to the soundboard); and

(2) by introducing a “pinch” or other aberration in a nut or saddle that alters the break point (or effectively adds another break point) you could change the pattern of reflection of wave energy in the string, change the mechanical impedance of the string, and create another set of standing waves

then potentially you could create another resonant frequency in the guitar top that could produce a wolf note

I’ll send a note off to Trevor Gore to see what he thinks of this conjecture.

[Neil Miller]

Not sure I follow your point #2. Can you elaborate?

The problem does seem to be accentuated when the player uses a capo.

If/when I get the guitar back I’ll try to share some recordings.

Neil

[Michael Minton]

It is pretty much a guess on my part. That’s why I have emailed Trevor, to see what he thinks about it. The hypothesis would be that if you actually have 2 different break points on the saddle (the “true” break point, and the “pinch” point), you have changed the system, and potentially the mechanical impedance, the distribution of string energy, and possibly created a different set of standing waves (as the string vibrates, some of the energy is admitted to the soundboard through the saddle/bridge, and some is reflected back into the string. The energy that is reflected back can produce standing waves.).

Might be complete BS.

[Giuliano Nicoletti]

Hello Neil,

What you describe looks like a classic wolf note, caused by the interaction between the soundboard’s primary resonance (the monopole, around 164 Hz) and the fretted note, E3, at 164.8 Hz. And yes, when the mobility of the soundboard is high at that frequency, you can hear a buzzing noise, and it can be quite nasty.

However, this type of problem is not typically covered by a warranty, so the reply from Gibson is understandable.

Fortunately, reducing the wolf note is feasible. You could try reducing stiffness by scalloping the bracing (specifically, the two lower V-braces). Alternatively, you could increase mass by switching from plastic to bone pins or by gluing a small weight of 3–5 grams under the bridge. (In the latter case, you can easily test this by temporarily taping the weight to the outside of the bridge to avoid damaging the finish.)

Keep in mind that both of these methods will also slightly lower the frequency of the soundboard’s first mode.

If you want to explore the relationship between these primary modes, there’s software available for free download here: https://www.iuliusguitars.com/my-research/

I would also suggest using REW (Room EQ Wizard) to take frequency response measurements. Investigating wolf notes requires precision, and REW is an excellent and free tool for the job.

Cheers,

Giuliano

iuliusguitars.com

My research | Iulius Guitars

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