Body
The function
of the strings discussed on the previous page is very important in the production
of sound by the guitar. By themselves, however, the strings make very little
sound. Because the strings are thin, they cut through the air without displacing
the air molecules much at all. It is the vibration of the body that creates
the distinctive sound of the guitar.
As mentioned
on the page discussing guitar parts, the bridge is attached to the sounding
board. The bridge acts as an anchor for the strings, which rest on the saddle.
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The vibrations from the strings travel through the saddle to the bridge,
and then to the sounding board. This causes the entire sounding board to
vibrate. The hollow body then amplifies the vibrations, causing disturbances
in the air. The sound produced then comes out of the sound hole allowing
the listener to hear the frequencies produced by the strings.
The purpose of
the body is to change the vibrations transmitted to it from the strings
into vibrations in the surrounding air molecules. The sounding board is
critical to this process. The back is not as important, acoustically at
most frequencies, in part because it is generally held snug to the body
of the person playing the guitar, thus damping its vibrations. The
sounding board is about 2.5 mm thick, and is usually made of a fine grained
wood, such as spruce, which allows it to vibrate fairly easily. The underside
of the sounding board has bracing on it. These braces serve different purposes.
Bracing patterns can be the difference between a good guitar, and a great
guitar.
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The most obvious reason for the bracing is to strengthen
the sounding board. Another reason for the bracing is to control the vibration
of the sounding board. As the vibrations are transferred into the body, resonance
waves are created. The result is resonance patterns in the sounding board.
The bracing patterns are designed in an attempt to control the pattern of
these resonance waves in order to cut down on interference, thus creating
a richer sound.
