From the October 2017 issue of Acoustic Guitar | BY MAMIE MINCH
Q: I have a newish Gibson Hummingbird, which overall I think is a great guitar. I haven’t had much issue with it. I take it in for setups once a year or so, but a few months ago, I started getting a loud, rattly buzz when I strum. It came and went for a while, but now it’s steady. What do you think is the most likely cause?
—George, Chattanooga, Tennessee
A: Ah, the buzz. Whenever I encounter the problem of the dreaded mystery buzz, I have a list of possible causes I run through. As with everything, a buzz is always in the last place you look, so I try to start with the simplest answer. I always bear in mind that the sound of a buzz can travel far from its origin, so sometimes you can’t trust your ears to tell you where the noise is originating.
How is my client’s fretting technique? Does their fingertip sit between the two frets, and are they giving firm pressure downward on the fingerboard, enough that the string doesn’t fish around on top of the next fret up? This common issue calls for some real tact in conversation with the player.
Low Nut Slot
Is one nut slot too low, causing the string to buzz along the top of that pesky first fret? If you press down the string at the first fret and the buzz is gone, you’ll know it was coming from the nut. Alternately, your low nut slot might give you a “back buzz”—this usually happens on the low E string, and can feel pernicious. It works like this: You get a metallic buzz when fretting or using a capo up the neck, but it’s quieted when you touch the string between the nut and where it’s fretted.
Poorly Cut Nut Slot
A nut slot should give the string a clear take-off point at the edge of the bone that meets the fingerboard. If the slot is cut so that the highest point is in the middle, or on the wrong edge, the string can buzz through the slot like a sitar. It’s the same idea with a saddle of any material—if the take-off point isn’t on the edge toward the soundhole, the string can buzz across its top.
Too Low an Action/Strung Too Light
While not the root cause of a buzz, trying for a very low action or using too light a gauge of strings can put a magnifying glass on little problems that you might otherwise never hear from. Things like . . .
Hitting a Fret
The sound of a string hitting the top of a fret is a pretty distinctive metallic buzz. If we think we hear that buzz, we want to know why. Is there a high fret, a low fret, or a fret that has bounced back up after we thought we’d seated it properly? Is the fingerboard warped, or ski-sloping at the fingerboard extension? Or do we have a . . .
Neck Without Enough Relief
If a neck is too straight or back-bowed, strings are bound to hit the tops of the frets as we play. If a taut string is a straight line and we create a sine wave when we agitate it, you can picture why we need at least a little relief in a neck. Your tech can help you figure out the right amount of relief for your style and instrument.
This is a kind of buzz that often migrates; it can make you feel really silly when you figure out that the annoying rattle that seemed to come from the body of your guitar was just a loose screw on the strap button or a tuner strip. Electric guitars can have loose pickup hardware.
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(Pro tip: Lots of older flattop Gibsons have bridges with two bolts fixing them to the top. The 1/4-inch nuts threaded up against the bridge plate can come a bit loose and rattle. If you didn’t know they were there, you’d be driven absolutely nuts looking for the explanation!)
Loose Brace or Glue Joint
While these tend to have a different quality of sound, wooden rather than metallic, they are still noisy and irritating. It’s especially audible in the case of a loose top brace in an acoustic guitar.
Your tech will test for this by thwacking a finger or thumb around the guitar’s top and back and listening for the sound of wood-knocking-into-wood.
Mamie Minch is the co-owner of Brooklyn Lutherie and an active blues player. She is the former head of repair at Retrofret Guitars.