Strings and Frets
www.musiciansfriend.com
There are six strings
on the standard acoustic guitar, each of which is tuned to a specific frequency,
or note. How the guitar produces the frequencies and tones discussed on
the previous page will be discussed on this one. A guitar takes advantage
of the fact that a string under tension will vibrate at a regular frequency.
The frequency of the string is dependent on four basic conditions: the
mass of the string, the tension of the string, the length of the
string, and the mode of vibration.
The effect of
the mode of vibration on the frequency is a complicated process, and will
not be discussed in detail here. In short, it deals with the harmonics used
by the guitar, which were discussed on the earlier page which dealt with
the production of sound. To learn more on this specific, further information
may be found on some of the sites listed in my bibliography.
Anyone looking
at a guitar is likely to notice that each of the strings has a different mass.
The first string is the thinnest, and the rest of the strings progressively
get thicker. The thicker strings vibrate more slowly, thus creating a lower
frequency. Since all of the strings use the same wavelength, the only way
for the strings to vary in frequency is by varying their masses or their tensions.
The amount the tensions can be varied is quite limited. In general, one
wants the strings to all be at about the same tension since, if a string
is not very tight, it becomes much more difficult to play. Because of this,
the importance of variable massed strings becomes obvious.
The tension of
the strings is controlled by the tuning pegs on the head of the guitar.
The tighter the strings are, the higher the frequency. When one tunes a
guitar, he/she is adjusting the tensions on the strings. It is very important
to get the tensions right, or the guitar will not produce harmonious sounds.
The length of
the strings is really what allows the guitar to be such a versatile instrument.
The other factors controlling frequency cannot be changed easily enough to
get the variance in sound needed for the guitar to create it's unique sound.
The length of a string that is free to vibrate can be easily changed by
holding the string against the fret board at the different fret positions.
The frequency is higher when the length of the string is shortened. The spacing
of the frets is by no means random. Each fret is placed so that the desired
frequency is produced when a string is pressed against it. The constant
used to figure fret spacing is 17.817. The length from the nut to the saddle
on most guitars is 24 to 26 inches. This is the distance over which the
strings are allowed to vibrate. Assuming that this distance is 26 inches,
it would be divided by 17.817 to find the distance from the nut to the first
fret(1.46 in.). Then the remaining distance from the first fret to the saddle
would again be divided by 17.817 in order to find the distance to the second
fret. The process is repeated all the way down the fret board. The photo
at the top of the page shows the spacing of the frets.
