We have implemented three different types of audio noise in Ghost Radio:

Brown / Red (supported in all versions)
Brown noise is named after botanist Robert Brown, who discovered Brownian motion (random particle motion) in the 1800s.
The change in sound signal from one moment to the next is random. Brown noise has a lot more energy at lower frequencies than it does at higher frequencies. Brown noise is sometimes referred to as red noise because it's somewhat analogous to red light, which has a low frequency.

White noise (supported in some versions)
Gets its name from white light. White light is a combination of all color frequencies, and white noise is similar since it’s a combination of all the different frequencies of sound humans can hear. The noise is the signal (frequency), created when all the different frequencies of audible sound that the human ear and brain can perceive are put together at a similar level. The sound of white noise we hear as humans therefore is the sound of all the frequencies between 20 and 20,000 Hertz

Pink
(supported in some versions)
As with white noise, pink noise contain all the frequencies that are audible to humans, but the way their signal power is distributed among those frequencies is different. White noise has equal power throughout all frequencies, while the power in pink noise decreases as the frequency increases. The pattern of pink noise occurs in a number of natural systems, including your daily heartbeat rhythms, quasar luminosity and traffic flow.

There are many more types of noise, but the above three are the most commonly used in the Paranormal community, especially White noise.

For more information, there is a good article on Wikipedia regarding this subject:
https://en.wikipedia.org/wiki/Colors_of_noise

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