Spectral color

What’s your favorite noise color: white, pink, brown, blue, purple, gray or black?

You’re probably familiar with white noise generators, which insomniacs often find useful as a sleep aid. White noise is a mixture of random frequencies with a flat spectrum – any frequency band has the same power as another. I find white noise to be crisp and harsh.

Here is an example of white noise (be careful, it’s noisy!)

Most white noise generators don’t emit white noise, they emit more soothing “colored noise”. Color noises have a mix of random frequencies, but some frequencies play louder than other frequencies. This gives the noise a distinctive “color” or tone. Here are examples of some common colored sounds:

  • pink noise differs from white noise – each octave contains the same amount of energy, rather than each frequency band as in white noise. It’s not as crisp as white noise. It’s richer, deeper. It looks like a rushing river.
  • brown noiseThe power decreases as the frequency increases. It looks like pink noise in the distance. It’s lush and chocolaty. I find it to be the most pleasant of all colored noises.
  • blue noiseSignal strength increases with higher frequencies. It looks like air escaping from an inflated tire. It is surprising rather than soothing.
  • purple noise is like blue noise but the power increases more strongly as the frequency increases. It sounds like a finer version of blue noise.
  • Gray noise is designed to accommodate a psychoacoustic equal volume curve “giving the listener the perception that they are equally loud at all frequencies”. I could probably fall asleep to gray noise, but it’s not as smooth as brown noise.
  • Black noise is silence. Here are 10 hours.

Wikipedia has a good article on noise colors with examples for each.

This originally appeared in my newsletter, The magnet.