Tuesday, February 9, 2010

Synthesis Made Simple: Part 4 - Bring the Noise - Noise Generators

Oscillators are fantastic for emulating (or inventing) pitched instrument sounds, but as you are well aware, many sounds don’t have a distinctive pitch. Whether you’re talking about the crack of a snare drum, the chiff of a flute note, the sound of a pick against a guitar string, or even the sound of the wind outside, noise is an essential ingredient in any self-respecting synth programmer's arsenal.

So what is noise?
Scientifically speaking, noise is a signal with a dense concentration of constantly changing, random frequencies of equal power. If that makes your eyes glaze over, just know that noise generally sounds like a steady hissing. To be a bit more accurate, what I described above is technically WHITE NOISE. This is the most commonly found noise generator, and generally speaking, usually when you’re talking about a noise generator, you’re probably talking about a white noise generator. Here's what white noise sounds like:

On some older or more advanced synths, however, you may have several types of noise available to you with PINK NOISE being the most common variant. These different types of noise have emphasis on different frequency ranges. The color-naming scheme refers to the spectral densities in different colors of light which is analogous to the spectral density of different audio frequencies present in the noise. In contrast to white noise, pink noise is a bit ‘bassier’ sounding, with BROWN or RED noise having still more emphasis on lower frequencies, and so on. These different types of noise can be helpful for emulating different types of sounds, but you’ll find that most of the time, WHITE NOISE does the trick just fine, which is why it’s the only type of noise you’ll find on the majority of synths.

And remember what I said about it being good for non-pitched sounds? You can actually give a pitch to noise through the use of the next item we’ll be discussing – filters.

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