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The Buzz on the Buzz
By Paul McGill

I think every guitarist at one time or another has a problem with the unwanted phenomenon of instrument vibration. The buzz what is it? Let's describe it as noise made when a vibrating part of the guitar comes into contact with another part of the guitar, which may or may not be also vibrating. The resulting sound can have its own frequency or can become a cacophony of noises not in the control of the player.

What are the most common causes? A list would include: string contact with the fret wire on the fingerboard; flatness of the saddle over which the strings rest, causing the strings to vibrate; poorly fitting nut slots, which cause the strings to vibrate against or inside the slot; loose strings or bridge pins; loose truss rod nut; loose or broken top or back brace; loose truss rod; loose top joint at sides; loose end pin jack nut; vibrating or loose tuning machine parts. Wow, I think I got most of the potential problems!

How can you determine what the buzz is and where it is being generated? First, does the problem only happen when you play a certain note, or does the problem happen no matter where you play on the fret board? Most loose parts make noises that are frequency related. Most fret noises or string buzzes are related to the geometry of the instrument's action setup. The most common buzzes are caused by action problems. Second, you want it to play how low? There are limits to what can be expected of the action height. However, a well set up instrument can be played with reasonable comfort depending on the demands of the player.

Let's go through a rundown of a number of indicators for action problems and their solutions, and then I will move on to the noises made by different body parts.

If a guitar buzzes at the first fret on an open string, the problem is the nut height. Many players want the nut height set very low. The height of the strings at the nut is usually higher than the fret heights. On electric guitars the nut height has to be low as possible for intonation purposes. However, if the nut height is set low on an acoustic guitar, there can be problems even if the strings clear the first fret. I call this problem back buzzing, where a string being depressed higher up the fret board picks up sympathetic vibration and buzzes between the frets and the strings between the fretted position of the hand and the nut. Say you are playing a B chord 7th position and the low E string starts rattling behind your hand. If this problem occurs on an electric guitar, it has no effect because the pick-up can't transmit the noise given its position at the bridge end of the strings. In both cases, either a buzz on an open string or a back buzz on a depressed string, the cure is to raise the nut. You can make a new nut, you can use bone dust or baking soda with super glue to build up the string height in the nut slot, or you can shim the nut from below. The most elegant cure is a new nut.

Another common problem is fret misalignment. The frets should be placed in a generally consistent plane, If one fret is to high the misalignment can cause the string to come into contact with that fret when playing the note one half step below. Fret noise is a funny thing. I have seen guitars where the frets were perfectly aligned, and still there was noise as if the frets where out of alignment from one end of the board to the other. Because the problem of string height over a fret is directly related to the diameter of the string's oscillation, the height of the strings required for noise-free playing can change, given the guitar's scale length and its top stiffness. I had a classical guitar made by a notable maker in my shop once that would not stop buzzing. The frets were accurately aligned, and still it buzzed. This guitar was very lively and had great oscillation of its strings. After much time spent studying the problem it became clear that the noise disappeared if the note was played with the finger depressing the string right on top of the fret. If the finger was moved back even an 1/8th of an inch, the buzz reappeared. The strings had so much amplitude that the strings would accelerate right off the fret, causing a buzz even though everything was properly aligned. I raised the action, the buzz got worse. The owner said he liked bass wire on his guitars, so I installed huge bass wire in an attempt to eliminate the problem. I was skeptical, but after installing the larger wire, the noise was greatly reduced. It was still there if the player wasn't careful, but it was manageable.

Getting back to geometry, if the strings buzz the entire length of the board the problem is either low action or a saddle buzz. Of course, that is if the beforementioned acceleration buzzing is not present. If the saddle is flat on its contact surface with the string, then the squared-off hind edge of the saddle will hold the string's down pressure on the saddle. The close proximity of the rest of the string's length across the saddle to the opposing edge of the saddle will provide an area where the oscillating string can buzz against the flat saddle surface. The cure is to reshape the saddle, if too flat, or raise the saddle height, if the action is too low.

The geometry of the action can be greatly altered by whether or not the neck is straight , convex, or concave along the distance of the fret board. When the neck is concave or bowed forward in its alignment, the action at the bridge must be lowered so that the strings are not too stiff under the player's fingers. As the strings are lowered the geometry of the action brings the strings into much closer proximity with the frets further up the fret board. This proximity will cause extra fret noise due to the action being too low in that area. When the neck is convex or back bowed, the action must be raised to keep the string's proximity acceptable in the central part of the fret board. This misalignment can make the action height higher up the finger board unplayably high.

Potential action problems are myriad, but I've covered the most common, so I will move on to body noise and loose parts. Most of these sounds can be located externally by using your hand to dampen a loose part. You should always check the simplest potential problems first, like a loose tuning machine screw, or even a string end vibrating against the guitar. I have seen guitars buzz in some strange places and have personally been stumped by a few which succeeded in hiding from me for hours while I poked and prodded through the joints of the instrument until I finally located an ever-so-slight joint failure between a top and a piece of lining. Truss rods can make interesting buzzing noises also. Fortunately, a syringe injection of glue puts a quick end to the raucous tones.

The internal joint failures are more directly diagnosed. You simply use your knuckles or fingers and tap the top and back plates listening for vibrations or rattles. Braces attached cross grain to a back or top are the must likely to come loose. This is because the lateral expansion and contraction of these surfaces cause great stress on the glue joints between the back or top and the brace. The action of the back or top attempting to slide back and forth against the brace is not unlike bending a piece of metal back and forth until it breaks. Once located, the loose parts must be reglued from inside the sound box by reaching through the sound hole. These repairs can become very interesting on a mandolin or an arch top guitar where you only have F holes to work through. These repairs can require very creative cures at times and are better left to those experienced in working inside the body where sometimes hands must be used as eyes to manipulate the problem areas.

The many causes of unwanted noise on your guitar can sometimes be rather pesky to locate or repair. Sometimes they are hard to diagnose because of environmental reasons, like the guy who told me about his custom made guitar that would buzz in his recording studio. He sent it back to the factory, but they couldn't locate the problem and returned it. It still buzzed. So this time he recorded the sound of the buzzing guitar and sent a tape of the guitar along with it back to the factory. They sent him a new guitar, which he didn't like as well and sold. The problem was most likely a loose joint in the guitar which would buzz when the humidity was such that it created less friction between the two parts.

I believe that there is not a buzz which can't be fixed. If one person can't find it for you, he may be lacking the insight to locate the problem. Hang in there, and eventually these things can come to light. [an error occurred while processing this directive]