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Old 19th March 2006, 11:23 AM   #1
Lyra is offline Lyra  Norway
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Question Digital Pink Noise generator...?

I've posted this (yesterday): Pink Noise generator under the Analog section.
I was told that I'll get more predictable results if I had implemented a digitally design.
But....I have never seen a decent digitally designed pink noise generator, or more actually a good design behind it...
If I was to to this, I haven't got a clue where to start.

Anybody in this section know how to do this ?

Any ideas would be appreciated

Lyra
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Old 19th March 2006, 11:51 AM   #2
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Get a National MM5837 noise source chip. 8 pin mini DIP. It is a digitally derived noise source. A National databook will have application notes for implementation, as does also their 1976 Audio Handbook where it appears on page 2-56.
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Old 19th March 2006, 01:16 PM   #3
Lyra is offline Lyra  Norway
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Can't seem to find this part (MM5837) anywhere. Seems like an obsolete chip !?

Searched the www, and came over this : http://www.edn.com/contents/images/80703di.pdf
A sollution using PIC12C508. Would this be a decent way generate the noise ?
(I've got a burner somewhere(?) that can burn theese chips too... )

I also found this one: http://www.discovercircuits.com/PDF-FILES/noisegen.pdf but I don't know what circuit would be the "best"

Lyra
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Old 19th March 2006, 04:36 PM   #4
gmarsh is offline gmarsh  Canada
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A quick hop on google reveals:

http://sound.westhost.com/project11.htm

Which looks like an acceptable project.

As for digital generation, I've written pink noise generation code for DSP - basically you use a random number generator feeding an appropriate FIR pink weighting filter. This requires quite a bit of DSP power, which a PIC12x simply can't do... but a dsPIC or another 'real' DSP should manage.
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Old 19th March 2006, 04:55 PM   #5
Lyra is offline Lyra  Norway
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gmarsh:
Hi.
Yes the project 11 on westhost was the basis (?) for my a "little different" inplementation posted under the analog section ( Pink Noise generator) , but the only reply I've got so far was to rather go for a digital solution.
How succeptible would such an analog noise-generator be when it comes to GSM noise in the nearby surrondings for instance ?

Lyra
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Old 20th March 2006, 01:37 PM   #6
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Quote:
Originally posted by gmarsh
As for digital generation, I've written pink noise generation code for DSP - basically you use a random number generator feeding an appropriate FIR pink weighting filter. This requires quite a bit of DSP power, which a PIC12x simply can't do... but a dsPIC or another 'real' DSP should manage.
Before you try pushing random numbers through a FIR filter, look at the Voss-McCartney method for generating pink noise. The programming is trivial.
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Old 20th March 2006, 03:29 PM   #7
gmarsh is offline gmarsh  Canada
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Quote:
Originally posted by Ulas
Before you try pushing random numbers through a FIR filter, look at the Voss-McCartney method for generating pink noise. The programming is trivial.
Voss-McCartney is a simple algorithm to look at.. but iIve found that when you're going for a given spectrum error, a VM algorithm actually requires more DSP power than a white generator + pinking filter.

VM requires generating many random numbers per sample - depending on the generator you use and the capabilities of the DSP, this can take several instructions per number. But DSPs can scream through a FIR/IIR.
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Old 20th March 2006, 04:47 PM   #8
moamps is offline moamps  Croatia
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In the picture below there is a decent pink noise generator from an old Elektor issue.

Regards,
Milan
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File Type: jpg pink_noise.jpg (62.3 KB, 210 views)
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Old 21st March 2006, 08:02 AM   #9
andrei is offline andrei  Canada
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The easiest way to do it is to just burn a computer-generated pink noise sample on a CD (or a Audio DVD). No hardware required .
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Old 21st March 2006, 09:50 AM   #10
Lyra is offline Lyra  Norway
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Quote:
Originally posted by andrei
The easiest way to do it is to just burn a computer-generated pink noise sample on a CD (or a Audio DVD). No hardware required .
Yes...I know, but this one have! to be portable, and preferable powered by "professional" phantom-power (48V)
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