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When the same note, say
middle C, is played on
different instruments,
the musical notes
produced sound
different.
This is because that as
well as producing the
FUNDAMENTAL FREQUENCY of
middle C they also
produce multiples of
this frequency called
HARMONICS.
The fundamental is a
pure sine wave.
The number and amplitude
of the harmonics
determines the
characteristic sound of
the instrument.
The harmonic which is
twice the fundamental
frequency, as in the
diagram, is called the
2nd harmonic.
The frequency which is
three times the
fundamental is the 3rd
harmonic.
The 3rd, 5th, 7th etc
are called ODD
harmonics.
The 2nd, 4th, 6th, 8th
etc are called EVEN
harmonics.
A square wave is made up
from a fundamental
frequency sine wave and
an infinite number of
odd harmonics.
A sawtooth wave form
consists of a
fundamental plus an
infinite number of even
harmonics.
If a sine wave is
injected into an
amplifier the output
wave form may be
distorted.
This may be due to
harmonics being
generated by the
amplifier.
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