Dr Bryan McEleney

Green Noise

Green Noise, like the extreme point known as silence, is an extreme edge in the musical space. It is characterised only by its frequency spectrum ( colour ), and the rest is random noise.

Examples of green noise occur wherever many sources of sound are mixed together - hundreds of wheels on tarmac, thousands of leaves blown by wind, waves of water crashing.

Here are some simulations of green noise, obtained by mixing two identical copies of a sound recording, with one copy randomly offset by a few seconds. By "folding" the recording many times, information is quickly smoothed away leaving green noise. The noise retains the frequency spectrum of the source recording.

This one was originally a music recording by Tom Waits

This one was originally an interview on the radio with two male voices

Technical Details

I used a small "C" program to read a file in Sun "au" format and write to an output file also in "au" format. This format is a simple 16 bit encoding of amplitude sampled at 44kHz. I have lost the original code, but here is a "C" program that generates a tone and outputs it to an au file. This code can be resued for basic manipulation of sound files.


If you have a specific frequency spectrum ( colour ) in mind, you can twiddle some knobs here to generate the corresponding noise.