http://whatis.techtarget.com/definition/0,,sid9_gci213526,00.html
White noise is a sound that contains every frequency within the range of human hearing (generally from 20 hertz to 20 kHz) in equal amounts. Most people perceive this sound as having more high-frequency content than low, but this is not the case. This perception occurs because each successive octave has twice as many frequencies as the one preceding it. For example, from 100 Hz to 200 Hz, there are one hundred discrete frequencies. In the next octave (from 200 Hz to 400 Hz), there are two hundred frequencies.
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Pink noise is a variant of white noise. Pink noise is white noise that has been filtered to reduce the volume at each octave. This is done to compensate for the increase in the number of frequencies per octave. Each octave is reduced by 6 decibels, resulting in a noise sound wave that has equal energy at every octave.
http://www.epanorama.net/documents/audio/noisetypes.html
White noise
White noise has equal power density across the entire spectrum (per Hz basis). White Noise has constant energy at all frequencies.
"white noise" was named such because it has an equal amount of power per Hz (or whatever your unit frequency) just like white light. true white noise (with infinite bandwidth) cannot exist since it has infinite power.
White noise is noise in which the intensity of the power spectral density is constant and independent of frequency. It is equivalent to saying that the signal power for a constant bandwidth centred at frequency fo, does not change if fo is varied.
Pink noise
Pink noise has uniform power density for a relative bandwidth (octave, decade, you-name-it). Pink noise has constant energy per constant percentage bandwidth. This equates to a -3dB/octave frequency response.
It's easy to turn white noise into pink noise by running it through a 3 dB/octave filter.
For example, an octave filter centered at 1kHz has half the bandwidth of an octave filter centered at 2kHz. If pink noise is driven into each filter with the same level, the output of each filter would be the same.
http://www.firstpr.com.au/dsp/pink-noise/
A stream of random numbers constitutes "white" noise Ð if listened to as an audio signal.Ê The "white" refers to the even distribution of wavelengths in white light, with a particular meaning in the audio or DSP sense:Ê that the power of the noise is distributed evenly over all frequencies, between 0 and some maximum frequency which is typically half the sampling rate.Ê For instance, white noise at a sampling rate of 44,100 Hz will have as much power between 100 and 600 Hz as between 20,000 and 20,500 Hz.Ê To our ears, this seems very bright and harsh.
A 1996 treatise by Joseph S. Wisniewski on the "Colors of Noise", including white, pink, orange, green . . . is at:Ê http://www.msaxon.com/colors.htm .Ê (Also at this site, Martin Saxon's description of the various weighting schemes for measuring noise:Ê http://www.msaxon.com/noise.htm .)
In the natural world, there are many physical processes which produce noise with what is known as a "pink" distribution of power.Ê "Pink" noise has an even distribution of power if the frequency is mapped in a logarithmic scale.Ê A straightforward example would be that there is as much noise power in the octave 200 to 400 Hz as there is in the octave 2,000 to 4,000 Hz.ÊÊ Consequently, it seems, our ears tell us that this is a "natural" even noise.