TODO!
white noise, pink noise, spectrum, probability density, ...
http://en.wikipedia.org/wiki/Colors_of_noise
choo choo effect: https://www.mail-archive.com/music-dsp@music.columbia.edu/msg03199.html
PortAudio ocean shore example: http://portaudio.com/docs/v19-doxydocs/paex__ocean__shore_8c.html
http://www.firstpr.com.au/dsp/pink-noise/
A New Shade of Pink:
http://stenzel.waldorfmusic.de/post/pink/
https://github.com/Stenzel/newshadeofpink
http://home.earthlink.net/~ltrammell/tech/pinkalg.htm
http://www.dsprelated.com/showarticle/908.php, Jupyter notebook
https://github.com/PaulStoffregen/Audio/blob/master/synth_pinknoise.h
https://github.com/PaulStoffregen/Audio/blob/master/synth_pinknoise.cpp
http://music.columbia.edu/pipermail/music-dsp/2002-May/049056.html
https://github.com/supercollider/supercollider/commit/7bc21edf596b2b3c8324880fbbbacdb342b85272
https://ccrma.stanford.edu/~jos/sasp/Example_Synthesis_1_F_Noise.html
http://www.noisemachine.com/talk1/
http://webstaff.itn.liu.se/~stegu/simplexnoise/simplexnoise.pdf
Python library: https://github.com/caseman/noise