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The Buzz on the Buzz
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.
By Paul McGill