RidgeRat
2006-03-26 22:48:21 UTC
Hi group. I'm a recently signed newbie. After some advice from Douglas,
the friendly list admin, I have posted information about a possibly new
algorithm for direct digital synthesis of pink noise. (Otherwise, you
can tell me about my re-discovery.) You can find the full exposition at
http://home.earthlink.net/~ltrammell/tech/pinkalg.htm
A little background: When searching the web for a pink noise generator
method suitable for semi-automated loudspeaker or microphone testing, I
found the "Pink Noise page" at
http://www.firstpr.com.au/dsp/pink-noise/
My initial joy at learning about the Voss-McCartney algorithm there was
quickly damped when I found that I did not get good quality results from
it. This is illustrated in the web page. Further study led to some
insights, and from there variations that I believe are improvements,
which is why I am here, where the experts lurk.
To summarize the page briefly --
Abstract. The Voss-McCartney direct digital synthesis algorithm
generates a noise process approximating pink noise, from an
equally-weighted combination of random white noise sources, on a rigid
updating schedule. It is conjectured that the rigid periodicity of the
updating explains spectral artifacts that prevent the method from
converging uniformly to a good approximation of the desired 1/f power
spectral density curve. Generalizing the method to an unbalanced
weighting of correlated random sources yields an algorithm that
produces relatively accurate approximations to the 1/f power spectrum
characteristic with fewer terms. There is roughly 0.15 dB approximation
error over a 7 octave range using six uniform pseudo-random variates per
output value. Useful results are obtained from as few as four uniform
variates per output.
If this sounds interesting, check out the page and feel free to comment
here. I'm especially interested in whether you observe the same results.
the friendly list admin, I have posted information about a possibly new
algorithm for direct digital synthesis of pink noise. (Otherwise, you
can tell me about my re-discovery.) You can find the full exposition at
http://home.earthlink.net/~ltrammell/tech/pinkalg.htm
A little background: When searching the web for a pink noise generator
method suitable for semi-automated loudspeaker or microphone testing, I
found the "Pink Noise page" at
http://www.firstpr.com.au/dsp/pink-noise/
My initial joy at learning about the Voss-McCartney algorithm there was
quickly damped when I found that I did not get good quality results from
it. This is illustrated in the web page. Further study led to some
insights, and from there variations that I believe are improvements,
which is why I am here, where the experts lurk.
To summarize the page briefly --
Abstract. The Voss-McCartney direct digital synthesis algorithm
generates a noise process approximating pink noise, from an
equally-weighted combination of random white noise sources, on a rigid
updating schedule. It is conjectured that the rigid periodicity of the
updating explains spectral artifacts that prevent the method from
converging uniformly to a good approximation of the desired 1/f power
spectral density curve. Generalizing the method to an unbalanced
weighting of correlated random sources yields an algorithm that
produces relatively accurate approximations to the 1/f power spectrum
characteristic with fewer terms. There is roughly 0.15 dB approximation
error over a 7 octave range using six uniform pseudo-random variates per
output value. Useful results are obtained from as few as four uniform
variates per output.
If this sounds interesting, check out the page and feel free to comment
here. I'm especially interested in whether you observe the same results.