:: GussetBLOG ::

:: Thursday, December 10, 2009 ::

Colo[u]rs of Noise

I came across the term “green noise” recently. White, Pink and Brown(ian) noise have strict mathematical definitions that I am well aware of, but there's a whole spectrum of other definitions out there, some more flexible than others. The wikipedia page is worth a read.

For example:

• Blue noise seems to be a term used in graphics dithering,
  
• A-weighted pink noise becomes Grey noise.
  
• Bands of zero energy are centered about the frequencies of musical notes in whatever scale is of interest. Since all in-tune musical notes are eliminated, the remaining spectrum could be said to consist of sour, citrus, or "Orange" notes.
  
• "Green noise is supposedly the background noise of the world. A really long term power spectrum averaged over several outdoor sites. Rather like pink noise with a hump added around 500 Hz."

I want to hear me some orange noise.
This green noise definition is interesting. I would have expected it to more closely resemble traffic noise (see fig below), but maybe that's because I live in a city. I’m going to look into this more as I survey noise levels all over the place anyway.


Normalized road traffic noise spectrum figure, from BS8233:1999

Labels: Acoustics, Maths

:: Dan 10.12.09 [Arc] [0 comments] [links to this post] ::
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