|<-- Back to Previous Page||TOC||Next Section -->|
Chapter 4: The Synthesis of Sound by Computer
Section 4.8: Granular Synthesis
When we discussed additive
synthesis, we learned that complex sounds can be created by adding together
a number of simpler ones, usually sets of sine waves. Granular synthesis
uses a similar idea, except that instead of a set of sine waves whose
frequencies and amplitudes change over time, we use many thousands of
very short (usually less than 100 milliseconds) overlapping sound
bursts or grains. The waveforms of these grains are often
sinusoidal, although any waveform can be used. (One alternative to sinusoidal
waveforms is to use grains of sampled sounds, either pre-recorded or captured
live.) By manipulating the temporal placement of large numbers of grains
and their frequencies, amplitude envelopes, and waveshapes, very complex
and time-variant sounds can be created.
Clouds of Sound
Granular synthesis is often used to create what can be thought of as "sound clouds"shifting regions of sound energy that seem to move around a sonic space. A number of composers, like Iannis Xenakis and Barry Truax, thought of granular synthesis as a way of shaping large masses of sound by using granulation techniques. These two composers are both considered pioneers of this technique (Truax wrote some of the first special-purpose software for granular synthesis). Sometimes, cloud terminology is even used to talk about ways of arranging grains into different sorts of configurations.
|<-- Back to Previous Page||Next Section -->|
©Burk/Polansky/Repetto/Roberts/Rockmore. All rights reserved.