This figure demonstrates the principle of superposition. At the top,
two sinusoids, A and B, are represented on the unit circle. Sinusoid
B has twice the frequency of sinusoid A, and so makes two rotations
about the circle in the time it takes sinusoid A to make one. The resulting time
waveform is the arithmetic sum of the projections of A and B on the vertical axis.
For example, in the
first time instant the projection of B on the vertical axis is 1, while
that of A is 0. The arithmetic sum of these projections is 1.
The superposition of many sinusoids results in a complex sound like that corresponding to speech or music.