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December 7, 2005
Think Pink
Pink Noise is a signal with even power distribution on a logarithmic frequency scale, pink noise masks background noise to help you concentrate.
Robin Whittle has a short paper on pink noise at "DSP generation of Pink (1/f) Noise", http://www.firstpr.com.au/dsp/pink-noise/
A stream of random numbers [generates] "white" noise – if listened to as an audio signal. The "white" refers to the even distribution of wavelengths in white light, with a particular meaning in the audio or DSP sense: 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. 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. 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 .... [can be found at] at: http://www.msaxon.com/colors.htm . (Also at this site, Martin Saxon's description of the various weighting schemes for measuring noise: 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. "Pink" noise has an even distribution of power if the frequency is mapped in a logarithmic scale. 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. Consequently, it seems, our ears tell us that this is a "natural" even noise.
Posted by sjc at December 7, 2005 9:49 AM
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