9. Sine Waves
Almost all sounds are made up of a number of frequencies that occur simultaneously. For example, a sound may contain frequencies of 100, 200, and 300 Hz at various amplitudes.
Waveforms that are made up of multiple frequencies are called complex waveforms.
When, however, a waveform consists of only one frequency that waveform is called a sine wave. The sine wave is the most fundamental of all waveforms because all other sounds are composed of sine waves that occur simultaneously at multiple frequencies, various amplitudes and phases.
Example 9-1: Sine waves consist of only one frequency. The sine wave is the most fundamental of all waveforms.
A musician synthesizing sound by combining frequencies of various amplitudes and phases is working with a process called additive synthesis.