Most people have probably heard the term "white noise" before, but apparently there are other colourful designations for different types of noise. Joining white, but less commonly known, are pink, brown/red, blue, violet and grey. The noise is classified by how the power changes as the frequency of the noise changes.
White noise, like white light, has a flat frequency spectrum. So it has equal power at each frequency. It can be used to mask background noise or even as a random number generator.
Pink noise falls logarithmically with frequency. So the amount of energy between 10 and 20 Hz is the same as between 1000 and 2000 Hz. This is the same as how humans hear so it's often used to test speakers and other audio equipment.
Brown noise falls off more quickly and is the kind of noise produced by Brownian motion. Blue and violet noise both increase in energy with increasing frequency. Grey noise has more energy at the top and bottom parts of the spectrum. The human ear hears each frequency equally loud so grey noise can be used to study hearing loss.
Not to be left out, black, green and orange noise are other unofficial colours. Check out wikipedia to listen to samples of the different types of noise and read more about them.
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