| All my reference books are at the office, so I'm straining my brain here.
But as I recall, pink noise is defined as equal power at every frequency
(or in each band), whereas white noise would be random - all frequencies
have equal occurence. This is what rand would generate.
So you would have to filter the output of rand by 1/freq. This would be
equivelent to halving the power for each doubling of frequency, or a low
pass filter having a slope of 3 dB/octave. Someone with better DSP chops
than mine would have to figure out how to do that. In fact, it might be
useful to have a random generator that outputs pink noise.
As a practical solution, you might set up an algorithm to adjust the gain
of the output of each Butterworth filter. Use a multiplying factor against
some reference band using the 1/freq ratio. What the multiplier is would
depend not only on the frequency ratio of the current band to the
reference, but also the bandwidth.
Hope this helps. Perhaps someone can tell us how a 3 dB/oct low pass filter
could be implemented.
-David.
At 02:58 PM 12/27/98 -0500, Brandon Nelson wrote:
>Can anyone tell me how to create pink noise? I've designed an instrument
>that uses Butterworth filtered noise to create a pipe-like sound, and it
>took me forever to realize why the low notes had no energy.
>
>--
>brandon_nelson@bigfoot.com
>ICQ: 11617296
>
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