Baffeled about buzzing

[stormin1155]

A friend of mine has a 12-string that was fretting out at the 12th fret. I offered to take a look at it. The 14th fret was high, so I leveled and recrowned it and dressed the surrounding frets and had it playing just fine. When I took it back to him he was trying it out and said, "the buzzing is still there." I told him I didn't hear it. He insisted it was still buzzing, only he was getting it at the 10th and 11th fret. I finally said I'd take it back home and take another look at it.

 

I pulled it out today and at first it seemed to play fine. When listenening very closely however, I could hear a slight harshness on the 2nd string, 11th fret. It didn't really sound like fret buzz. I wondered if it was perhaps just a natural frequency peak of the guitar that is emphasized by the two strings being not being perfectly in tune. I tuned it down a step, and the harshness dropped a couple frets, tuned it back up and I didn't notice it.

 

Any thoughts as to what is causing this? I know my friend's ears are much more sensitive to high frequencies than mine are. Have any of you had any experience with "wolf tones" or harmonics from 12 strings?

[bjorn-fjord]

Most guitars have a note that matches the resonant frequency of some component of the instrument. Often a single note will be markedly louder or quieter depending on whether the resonant frequency is matching the note or cancelling it. Usually it's a note on the high E string for some reason.

 

Often it is the neck itself that causes this conflict. What's happening is that the neck (for example) is vibrating at the same frequency as the note that is being played. Depending on whether or not this note is in exact phase with the component of the guitar that is vibrating, the note on the guitar string will lose or gain energy from the sympathetic vitbration. In the worst cases this note matches the resonant frequency of the the truss rod. This can cause a loud rattling sound inside the neck.

 

In any case, there's really not much that can be done to fix it. If the problem doesn't seem to relate to a particular mechanical issue such as a high fret I would explain to your friend that this is just a quirk with this guitar. Every guitar has its quirks.

[Gary Palmer]

Bjorn's advice is solid. Still on the topic of frequencies, it's also possible that;

 

1. Another string may be ringing in sympathy to the one being played.

2. The buzz could be coming from a poorly cut nut slot.

3. Check for a loose/poorly fitted fret.

4. Potential truss rod buzz.

5. Check for splinters of wood/debris where pin holes have been drilled through the bridge plate. Stray splinters can sometimes lead to odd buzzing effects.

6. Check tuners are tightened into place.

7. Capo at the 11th fret and check clearances between frets and strings.

 

This kind of buzzing tends to be the worst to try and source and a little like hearing a rattling noise from somewhere inside a car, but being unable to locate it's origin. You try everything, before realising it's simply a seat-belt slipping back into place, or your wife's lip-stick rolling around in the glove box.

 

We had a guitar come into the shop once with an odd sounding buzz that seemed to eminate from the neck and it finally turned out to be a loosely fitted end-pin. It would have stumped Sherlock Holmes and had all of us baffled - after trying and checking everything - until my nephew popped into the shop on one of his visits and fiddled with the newly replaced end-pin.