makes your guitar or bass sound they way YOU like it?
You would probably agree that there
are countless things that effect tone. At the very core of any
guitar or bass is the string set. Without strings, there would
be no sound. The string set is where it all begins.
WARNING: This section of Professor String
covers the science of guitar string tone and frequency.
Many of you out there may find science to be a boring topic full
of brain twister jargon and mathematics. In some respects, this
is true. Consider this:
It's boring when compared to playing a killer tune on
your ax and having the audience eat up every bit of it.
when compared to playing some cool riffs on a rare vintage
when compared to sitting in a jam session with a well known
when compared to.......well, you get the idea. So, why bother
check'n out this section??? If you skip this information, then
YOU will be missing out on something most other musicians do not
At the heart of every sound is a
vibration. Whether it is a speaker, a drum, or a string, the vibration of these
objects are the origins of sound. Sometimes the contents of an object will
vibrate to make sound. An example would be blowing into a jug to make sound. The
air within the jug will oscillate in a vibratory manner giving off a sound.
Within each vibration is a frequency, or rate of speed that the vibration
occurs. Each object has it's own speed at which it will vibrate when it is
struck or strummed. This is known as and objects Natural Frequency. Not all
vibrations can be heard. In order to become audible by the human ear, the
vibration needs to be great enough to create oscillations of pressure. We know
the oscillations of pressure to be commonly called "sound waves." Sound waves
are produced by vibrations with higher amplitudes.
The Origin of Tone
Most everything has a natural frequency associated with
it, including a musical instrument string. However, not everything has a "good"
sounding natural frequency. There are many frequency complexities that makes
something sound clear versus something that sounds like noise. Dropping a piece
of scrap metal on the floor produces a complex noise sound. Blowing through a
piccolo also produces a pure tone sound. The two are completely different in
their quality of sound. This quality is often referred to as the timbre of
sound. Much of the sound timbre has to do with the object having a single
frequency in it's sound. Things that produce a cleaner frequency without odd
frequency components being introduced, are said to have a pure tone, and can be
musical. Objects that have a set of frequencies that produce a whole number
mathematical relationship can produce a thick and very rich sound like the low B
string on a 5-string bass. Yet, other things can vibrate, with and odd number of
multiple frequencies, and sound like noise. These multiple frequencies are often
mathematically unrelated and do not establish a whole number mathematical
relationship. Again, the resulting vibration sounds like noise in this scenario.
much everything that has a repetitive, cyclical motion, will produce a
frequency. If you were to flap your arms up and down, there would be a frequency
associated with your motion. When you wave your hand back and forth to wave
hello, there is a frequency associated with your motion. A fan blade spinning
has a frequency associated with it. A vibrating guitar string has a frequency
associated with it. In each one of these cases, there is a frequency that can,
or cannot be heard. The basic relationship is this:
frequency = speed/wavelength
the speed of motion or size of the wave pattern changes, there will be a change
in frequency. In this case, it is natural frequency we are talking about. There
are many variables that can effect the natural frequency of a guitar string. As
a guitarist, you are able to change the natural frequency of string anytime you
press down on a fret. This shortens the vibrating portion of a string. The
shorter portion produces a smaller sized wavelength that vibrates at a higher
speed. If you look back at our frequency equation, this means the higher speed
divided by a smaller wavelength yields a higher frequency. So, each time you
progress up the frets on the fretboard, the frequency goes up. There are other
variables that effect the frequency of the string, as stated earlier. On a
guitar we have strings that have different tensions and mass densities. The
heavier strings vibrate more slowly due to the increased mass and less tension.
Higher tensions create shorter, and faster cycles of movement. Thin strings have
less mass, and tend to have less inertia in their movement. This allows them to
produce a faster vibration speed with a quicker decay. You will notice that a
high E string fingered on the 20th fret decays much quicker than a low E string
played open. In short, tension has a profound effect on the wavelength and speed
of vibration. The density of the string's material will also have an effect on
it's ability to carry a wave at a particular speed. Strings that are dirty and
have corrosion are also effecting the natural frequency of the string. The dirt
and corrosion are adding mass to a string. The added mass (dirt) makes the
string vibrate slower and can act as a dampener in it's ability to carry a wave.
Again, this effects speed and wavelength. Thus effecting the frequency
components of a string.
from Natural Frequency
frequency of a guitar string can be more difficult to hear
without an adjoining structure to resonate with it. As a string
is plucked, kinetic energy, in the form of vibration, is
transferred to the string. Yet, the string itself does not have
the surface area to make the vibrations highly audible. It needs
to rely on other particles to vibrate and generate sound waves.
In essence, a transfer and dissipation of the kinetic energy
needs to occur to other objects like an acoustic guitar's
soundbox. The guitar's soundbox will accept the kinetic energy
from the string and start the air particle inside to vibrate.
The transferred vibration will be in the same frequency of the
string's natural frequency. This transferring of vibration is
known as forced vibration. There will also be a pressure build
up within the soundbox as the moving air particles are needing
to release energy and sound waves. The pressure, in the form of
sound waves, will come through the soundbox's sound hole(s).
Acoustic guitars with solid tops (versus laminated) have an
advantage of transferring more forced vibrational energy due to
the uniformity of a solid piece of wood versus layered laminated
tops. Solid body guitars do not rely upon forced vibration energy
to transfer sound in the same manner as an acoustic guitar. The
string's vibrational energy and natural frequency are captured
with a magnetic transducer or pressure transducer.
situations you may notice a string starting to vibrate by itself
when other soundwaves, of similar frequency, are present in the
room. The string will start to vibrate without being plucked or
strummed. The only thing connecting the string with the other
soundwaves is purely air. When the particles that make up air
begin to vibrate at the same at the same natural frequency as
the string, they set the string into motion at it's natural
frequency. This phenomenon is know as resonance. Resonance is
one of the building blocks that makes up audio feedback in a
system. In a setup with an acoustic guitar and a PA system, the
speaker vibrates at the same natural frequency of a string on
the guitar and forces it into vibrational motion. The overall
effect of this system resonance creates feedback between the
acoustic guitar and the PA system.
string plays at its natural frequency, there is an associated
reflected wave pattern that occurs within the string itself. A
reflection occurs at the end of the string and travels back
towards it's origin. As it travels back towards its origin, it
will interfere with incident waves from the source in such a
manner that specific points along the medium appear to be
standing still. The reflected wave is continuously repeated and
is often called a standing wave. Standing waves can be heard at
various vibrational nodes on a guitar string. These standing
wave patterns are only created along various points of the
string and occur at certain frequencies. These frequencies are
known as harmonic frequencies. Most guitarist refer to the
harmonic frequencies as harmonics. The harmonic frequency
generated by a string has a distinctive tone that sounds
distinctive and "bell like" in its tone.