An Audio Synthesis Textbook For Musicians, Digital Artists and Programmers by Mike Krzyzaniak

3 Envelopes

Explanation of the Concepts

All of the signals studied in the previous chapter were periodic, which is to say that the basic shape of the waveform was repeated over and over ad infinitum. An envelope is a non-periodic signal, whose shape is executed only once. For this reason, envelopes cannot generally be used create sound, but are used to control some aspect of the sound. The most common use of envelopes is to control the amplitude of a sound over time. Thus, sounds can be given sharp, percussive attacks, long gradual decays and so forth. This is the use that will be focused upon here, but once the envelope has been calculated, it can easily be applied to other variable aspects of the sound, such as pitch, pulse-width, panning, or other aspects to be discussed in subsequent chapters.