7.
Complex Sounds.
a. Harmonics. Most
of the sound used in telephony
is not as simple as that
illustrated in figure 3. The
type of sound we hear or use in
telephony is called complex
sounds.
Complex sounds
consist of two or more simple
sounds each having its own
frequency and amplitude. Any
complex sound may be
separated rated into its
component simple sounds and
their frequencies as shown in
figure 4. The lowest frequency
contained in this complex
sound is called the fundamental
frequency sometimes referred
to as simply the fundamental.
All others are called harmonic
frequency
or
overtones.
Harmonic frequencies are
whole-number multiples of the
fundamental. For example, if
the fundamental frequency of a
sound is 400 cycles the fourth
harmonic would be four times
(4x) the fundamental or 1600
FIGURE 4. Analysis of Complex Waveform
cycles, or the fifth harmonic =
5 x 400 or 2,000 cycles. With
this definition then we could
say the fundamental is the first
harmonic of a frequency of
sound.
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