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[sdiy] Various colors of noise.

[sdiy] Various colors of noise.

2026-03-02 by Thomas Hudson

I have an analog module that can generate blue, white, pink, and red (brownian) noise. I’m interested in how I might create a random walk using perhaps a sample/hold and smoothing function to produce a sort of wandering control voltage from each of these noise sources.

I also was recently introduced to green noise. From Wikipedia:

  • The mid-frequency component of white noise, used in halftonedithering[19]
  • Bounded Brownian noise
  • Vocal spectrum noise used for testing audio circuits[20]
  • Joseph S. Wisniewski writes that "green noise" is marketed by producers of ambient sound effects recordings as "the background noise of the world". It simulates the spectra of natural settings, without human-made noise. It is similar to pink noise, but has more energy in the area of 500 Hz.

Wondering how I might generate this other than using something like a bandpass filter tuned to 500 Hz using pink noise. I want to generate it in the analog realm.

TIA,
Thomas


Re: [sdiy] Various colors of noise.

2026-03-03 by Emily Straight

is there any statistical difference between different colors of noise after going through a sample-and-hold? i'd figured on longer timescales every possible voltage is equally likely anyway, so you wouldn't be able to tell the difference.
Show quoted textHide quoted text
On Mon, Mar 2, 2026, 3:26 PM Thomas Hudson via Synth-diy <synth-diy@synth-diy.org> wrote:
I have an analog module that can generate blue, white, pink, and red (brownian) noise. I’m interested in how I might create a random walk using perhaps a sample/hold and smoothing function to produce a sort of wandering control voltage from each of these noise sources.

I also was recently introduced to green noise. From Wikipedia:

  • The mid-frequency component of white noise, used in halftonedithering[19]
  • Bounded Brownian noise
  • Vocal spectrum noise used for testing audio circuits[20]
  • Joseph S. Wisniewski writes that "green noise" is marketed by producers of ambient sound effects recordings as "the background noise of the world". It simulates the spectra of natural settings, without human-made noise. It is similar to pink noise, but has more energy in the area of 500 Hz.

Wondering how I might generate this other than using something like a bandpass filter tuned to 500 Hz using pink noise. I want to generate it in the analog realm.

TIA,
Thomas


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Re: [sdiy] Various colors of noise.

2026-03-03 by Thomas Hudson

Yes very much different. There’s an old article in Scientific American by Marvin Gardner, that shows that music statically follows 1/f  or pink noise.

Note selection by red or brown noise is very boring. Imagine you have a random set of five dice to select the next note. Red / brown is only rolling  one of the dice for every selection.

Random sampled noise at any specific color frequency still follows the statistical likelihood of the next sample for that color..

There’s great way to hear the difference:

-  Colored noise, clocked sample / hold, quantizer, note selection.

The note selection differences are very apparent.

Though it would be interesting to plot the curves at various sample rates.
Show quoted textHide quoted text
> On Mar 2, 2026, at 8:31 PM, Emily Straight <emily.tw.straight@gmail.com> wrote:
> 
> is there any statistical difference between different colors of noise after going through a sample-and-hold? i'd figured on longer timescales every possible voltage is equally likely anyway, so you wouldn't be able to tell the difference.
> 
> On Mon, Mar 2, 2026, 3:26 PM Thomas Hudson via Synth-diy <synth-diy@synth-diy.org <mailto:synth-diy@synth-diy.org>> wrote:
>> I have an analog module that can generate blue, white, pink, and red (brownian) noise. I’m interested in how I might create a random walk using perhaps a sample/hold and smoothing function to produce a sort of wandering control voltage from each of these noise sources.
>> 
>> I also was recently introduced to green noise. From Wikipedia:
>> 
>> The mid-frequency component of white noise, used in halftone <https://en.wikipedia.org/wiki/Halftone>dithering <https://en.wikipedia.org/wiki/Dithering>[19] <https://en.wikipedia.org/wiki/Blue_noise#cite_note-19>
>> Bounded Brownian noise
>> Vocal spectrum noise used for testing audio circuits[20] <https://en.wikipedia.org/wiki/Blue_noise#cite_note-comp.dsp_FAQ-20>
>> Joseph S. Wisniewski writes that "green noise" is marketed by producers of ambient sound effects recordings as "the background noise of the world". It simulates the spectra of natural settings, without human-made noise. It is similar to pink noise, but has more energy in the area of 500 Hz.
>> 
>> Wondering how I might generate this other than using something like a bandpass filter tuned to 500 Hz using pink noise. I want to generate it in the analog realm.
>> 
>> TIA,
>> Thomas
>> 
>> 
>> ________________________________________________________
>> This is the Synth-diy mailing list
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Re: [sdiy] Various colors of noise.

2026-03-03 by brianw

The probability distribution of the values in a random sequence are completely independent of the frequency spectrum of those values as a signal.

First order probability distribution is uniform, and this is what the simplest mathematical computer noise sources produce. Second order is Triangular Probability Distribution Function (TPDF), or the sum or average of two uniform sources. Increasing the order to infinity yields Gaussian distribution, which is how nature presents values for most things, like Brownian motion, i.e., resistor noise, and that's probably why it's called "normal distribution." Chapter 2 of The Scientist and Engineer's Guide to Digital Signal Processing gives a shortened formula for creating a Gaussian distribution from two uniformly distributed values (rather than an infinite series).

These distributions of noise all seem to sound the same when implemented, but if used in a process as a modulator, then the derivative of the probability distribution may affect the sound, making higher order distribution "curves" less objectionable.

I assume that most nature sounds are attenuated according to distance, with high frequencies falling off faster than lower frequencies. I recommend investigating Stokes law of sound attenuation.

Anyway, I suspect that all nature sounds start with normal distribution and are simply filtered by the air. I would not bother with too complicated a filter if you only want ambient sounds.

Brian
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On Mar 2, 2026, at 6:15 PM, Thomas Hudson wrote:
> Yes very much different. There’s an old article in Scientific American by Marvin Gardner, that shows that music statically follows 1/f  or pink noise.
> 
> Note selection by red or brown noise is very boring. Imagine you have a random set of five dice to select the next note. Red / brown is only rolling  one of the dice for every selection.
> 
> Random sampled noise at any specific color frequency still follows the statistical likelihood of the next sample for that color..
> 
> There’s great way to hear the difference:
> 
> -  Colored noise, clocked sample / hold, quantizer, note selection.
> 
> The note selection differences are very apparent.
> 
> Though it would be interesting to plot the curves at various sample rates.
> 
> On Mar 2, 2026, at 8:31 PM, Emily Straight <emily.tw.straight@gmail.com> wrote:
>> is there any statistical difference between different colors of noise after going through a sample-and-hold? i'd figured on longer timescales every possible voltage is equally likely anyway, so you wouldn't be able to tell the difference.
>> 
>> On Mon, Mar 2, 2026, 3:26 PM Thomas Hudson wrote:
>>> I have an analog module that can generate blue, white, pink, and red (brownian) noise. I’m interested in how I might create a random walk using perhaps a sample/hold and smoothing function to produce a sort of wandering control voltage from each of these noise sources.
>>> 
>>> I also was recently introduced to green noise. From Wikipedia:
>>> 
>>> 	• The mid-frequency component of white noise, used in halftonedithering[19]
>>> 	• Bounded Brownian noise
>>> 	• Vocal spectrum noise used for testing audio circuits[20]
>>> 	• Joseph S. Wisniewski writes that "green noise" is marketed by producers of ambient sound effects recordings as "the background noise of the world". It simulates the spectra of natural settings, without human-made noise. It is similar to pink noise, but has more energy in the area of 500 Hz.
>>> 
>>> Wondering how I might generate this other than using something like a bandpass filter tuned to 500 Hz using pink noise. I want to generate it in the analog realm.
>>> 
>>> TIA,
>>> Thomas
>

Re: [sdiy] Various colors of noise.

2026-03-03 by rburnett@richieburnett.co.uk

If the ZIP attachment makes it through it contains five examples of 
"white noise" created with different amplitude distributions:

1. Gaussian distribution
2. Uniform (all amplitudes equally likely)
3. Triangular distribution
4. Two discrete levels (Digital PRBS)
5. Three discrete levels (Two digital sources added together)

See if you can tell the difference by listening!

-Richie,
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On 2026-03-03 07:21, brianw wrote:
> The probability distribution of the values in a random sequence are 
> completely independent of the frequency spectrum of those values as a 
> signal...

Re: [sdiy] Various colors of noise.

2026-03-03 by Tom Wiltshire

+1 agree with Richie and Brian.

The "noise colour" (frequency spectrum) and amplitude distribution are independent. It kind-of blew my mind when I first discovered this, since (in my head at least) you'd have thought that such a significant difference in the signals would be audible, but it's really not. You can make "white noise" with all of these different flavours, as Richie has done, and it'll affect the output of an S+H sampling them, but not the sound as audio.
Show quoted textHide quoted text
> On 3 Mar 2026, at 10:01, rburnett@richieburnett.co.uk wrote:
> 
> If the ZIP attachment makes it through it contains five examples of "white noise" created with different amplitude distributions:
> 
> 1. Gaussian distribution
> 2. Uniform (all amplitudes equally likely)
> 3. Triangular distribution
> 4. Two discrete levels (Digital PRBS)
> 5. Three discrete levels (Two digital sources added together)
> 
> See if you can tell the difference by listening!
> 
> -Richie,
> 
> 
> On 2026-03-03 07:21, brianw wrote:
>> The probability distribution of the values in a random sequence are completely independent of the frequency spectrum of those values as a signal...
> <noise.zip>________________________________________________________
> This is the Synth-diy mailing list
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Re: [sdiy] Various colors of noise.

2026-03-03 by mark verbos

I don’t know if this answers any question, but it is interesting. It explains why Buchla sampled a triangle wave hard synched to noise rather than sampling noise in the Source of Uncertainty.

Mark

Re: [sdiy] Various colors of noise.

2026-03-03 by rburnett@richieburnett.co.uk

You start to hear the difference at extremes...  The attached WAV has 
2-level (digital) noise but now with very sparse positive pulses.  (Low 
97% of the time.  High 3% of the time.)  The long-term power spectral 
density is still that of "white noise", the same as the previous 
examples.  As you reduce the probability of the pulses it starts to 
sound more like frying bacon, "popcorn noise", or eventually like 
"surface noise" on old vinyl records!

-Richie,
Show quoted textHide quoted text
On 2026-03-03 10:31, Tom Wiltshire wrote:
> +1 agree with Richie and Brian.
> 
> The "noise colour" (frequency spectrum) and amplitude distribution are 
> independent. It kind-of blew my mind when I first discovered this, 
> since (in my head at least) you'd have thought that such a significant 
> difference in the signals would be audible, but it's really not. You 
> can make "white noise" with all of these different flavours, as Richie 
> has done, and it'll affect the output of an S+H sampling them, but not 
> the sound as audio.
> 
>> On 3 Mar 2026, at 10:01, rburnett@richieburnett.co.uk wrote:
>> 
>> If the ZIP attachment makes it through it contains five examples of 
>> "white noise" created with different amplitude distributions:
>> 
>> 1. Gaussian distribution
>> 2. Uniform (all amplitudes equally likely)
>> 3. Triangular distribution
>> 4. Two discrete levels (Digital PRBS)
>> 5. Three discrete levels (Two digital sources added together)
>> 
>> See if you can tell the difference by listening!
>> 
>> -Richie,
>> 
>> 
>> On 2026-03-03 07:21, brianw wrote:
>>> The probability distribution of the values in a random sequence are 
>>> completely independent of the frequency spectrum of those values as a 
>>> signal...
>> <noise.zip>________________________________________________________
>> This is the Synth-diy mailing list
>> Submit email to: Synth-diy@synth-diy.org
>> View archive at: https://synth-diy.org/pipermail/synth-diy/
>> Check your settings at: 
>> https://synth-diy.org/mailman/listinfo/synth-diy
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Re: [sdiy] Various colors of noise.

2026-03-03 by Tom Wiltshire

Notice that the triangle wave, the sawtooth wave, and the psuedo-random binary level noise uniform distribution (Phew! What a mouthful!) all have the same uniform probability distribution.
Show quoted textHide quoted text
> On 3 Mar 2026, at 12:49, mark verbos <markverbos@gmail.com> wrote:
> 
> I don’t know if this answers any question, but it is interesting. It explains why Buchla sampled a triangle wave hard synched to noise rather than sampling noise in the Source of Uncertainty.
> 
> Mark
> 
> 
> 
> 
> 
> <federal.jpg>
> 
>> On Mar 3, 2026, at 11:31, Tom Wiltshire <tom@electricdruid.net> wrote:
>> 
>> +1 agree with Richie and Brian.
>> 
>> The "noise colour" (frequency spectrum) and amplitude distribution are independent. It kind-of blew my mind when I first discovered this, since (in my head at least) you'd have thought that such a significant difference in the signals would be audible, but it's really not. You can make "white noise" with all of these different flavours, as Richie has done, and it'll affect the output of an S+H sampling them, but not the sound as audio.
>> 
>>> On 3 Mar 2026, at 10:01, rburnett@richieburnett.co.uk wrote:
>>> 
>>> If the ZIP attachment makes it through it contains five examples of "white noise" created with different amplitude distributions:
>>> 
>>> 1. Gaussian distribution
>>> 2. Uniform (all amplitudes equally likely)
>>> 3. Triangular distribution
>>> 4. Two discrete levels (Digital PRBS)
>>> 5. Three discrete levels (Two digital sources added together)
>>> 
>>> See if you can tell the difference by listening!
>>> 
>>> -Richie,
>>> 
>>> 
>>> On 2026-03-03 07:21, brianw wrote:
>>>> The probability distribution of the values in a random sequence are completely independent of the frequency spectrum of those values as a signal...
>>> <noise.zip>________________________________________________________
>>> This is the Synth-diy mailing list
>>> Submit email to: Synth-diy@synth-diy.org
>>> View archive at: https://synth-diy.org/pipermail/synth-diy/
>>> Check your settings at: https://synth-diy.org/mailman/listinfo/synth-diy
>>> Selling or trading? Use marketplace@synth-diy.org
>> 
>> 
>> ________________________________________________________
>> This is the Synth-diy mailing list
>> Submit email to: Synth-diy@synth-diy.org
>> View archive at: https://synth-diy.org/pipermail/synth-diy/
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>

Re: [sdiy] Various colors of noise.

2026-03-03 by Mike Beauchamp

Hi Thomas,
Maybe take all of the different noises, and feed them into an 
interpolating scanner circuit (like this one: 
https://till.com/articles/scanner/ ) and from there you could control 
the output noise colour (and anything inbetween) with the wandering CV.

I wonder if the different noise colours all need to be derived from a 
single source for the crossfading to work.

Mike
Show quoted textHide quoted text
On 2026-03-02 18:20, Thomas Hudson via Synth-diy wrote:
> I have an analog module that can generate blue, white, pink, and red 
> (brownian) noise. I’m interested in how I might create a random walk 
> using perhaps a sample/hold and smoothing function to produce a sort of 
> wandering control voltage from each of these noise sources.
> 
> I also was recently introduced to green noise. From Wikipedia:
> 
>   * The mid-frequency component of white noise, used in halftone
>     <https://en.wikipedia.org/wiki/Halftone>dithering
>     <https://en.wikipedia.org/wiki/Dithering>^[19]
>     <https://en.wikipedia.org/wiki/Blue_noise#cite_note-19>
>   * Bounded Brownian noise
>   * Vocal spectrum noise used for testing audio circuits^[20]
>     <https://en.wikipedia.org/wiki/Blue_noise#cite_note-comp.dsp_FAQ-20>
>   * Joseph S. Wisniewski writes that "green noise" is marketed by
>     producers of ambient sound effects recordings as "the background
>     noise of the world". It simulates the spectra of natural settings,
>     without human-made noise. It is similar to pink noise, but has more
>     energy in the area of 500 Hz.
> 
> 
> Wondering how I might generate this other than using something like a 
> bandpass filter tuned to 500 Hz using pink noise. I want to generate it 
> in the analog realm.
> 
> TIA,
> Thomas
> 
> 
> 
> ________________________________________________________
> This is the Synth-diy mailing list
> Submit email to: Synth-diy@synth-diy.org
> View archive at: https://synth-diy.org/pipermail/synth-diy/
> Check your settings at: https://synth-diy.org/mailman/listinfo/synth-diy
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Re: [sdiy] Various colors of noise.

2026-03-03 by Thomas Hudson

Interesting idea and article.
Show quoted textHide quoted text
> On Mar 3, 2026, at 4:58 PM, Mike Beauchamp <list@mikebeauchamp.com> wrote:
> 
> Hi Thomas,
> Maybe take all of the different noises, and feed them into an interpolating scanner circuit (like this one: https://till.com/articles/scanner/ ) and from there you could control the output noise colour (and anything inbetween) with the wandering CV.
> 
> I wonder if the different noise colours all need to be derived from a single source for the crossfading to work.
> 
> Mike
> 
> 
> On 2026-03-02 18:20, Thomas Hudson via Synth-diy wrote:
>> I have an analog module that can generate blue, white, pink, and red (brownian) noise. I’m interested in how I might create a random walk using perhaps a sample/hold and smoothing function to produce a sort of wandering control voltage from each of these noise sources.
>> I also was recently introduced to green noise. From Wikipedia:
>>  * The mid-frequency component of white noise, used in halftone
>>    <https://en.wikipedia.org/wiki/Halftone>dithering
>>    <https://en.wikipedia.org/wiki/Dithering>^[19]
>>    <https://en.wikipedia.org/wiki/Blue_noise#cite_note-19>
>>  * Bounded Brownian noise
>>  * Vocal spectrum noise used for testing audio circuits^[20]
>>    <https://en.wikipedia.org/wiki/Blue_noise#cite_note-comp.dsp_FAQ-20>
>>  * Joseph S. Wisniewski writes that "green noise" is marketed by
>>    producers of ambient sound effects recordings as "the background
>>    noise of the world". It simulates the spectra of natural settings,
>>    without human-made noise. It is similar to pink noise, but has more
>>    energy in the area of 500 Hz.
>> Wondering how I might generate this other than using something like a bandpass filter tuned to 500 Hz using pink noise. I want to generate it in the analog realm.
>> TIA,
>> Thomas
>> ________________________________________________________
>> This is the Synth-diy mailing list
>> Submit email to: Synth-diy@synth-diy.org
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> ________________________________________________________
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Re: [sdiy] Various colors of noise.

2026-03-03 by Thomas Hudson

BTW, while researching creating green noise I came across a website for a Mac and iOS app:

https://simplynoise.com/

In addition to noise colors, t also has beach sounds, fireplaces, babbling brooks, etc.

Fun little app.
Show quoted textHide quoted text
> On Mar 3, 2026, at 5:56 PM, Thomas Hudson via Synth-diy <synth-diy@synth-diy.org> wrote:
> 
> Interesting idea and article. 
> 
>> On Mar 3, 2026, at 4:58 PM, Mike Beauchamp <list@mikebeauchamp.com> wrote:
>> 
>> Hi Thomas,
>> Maybe take all of the different noises, and feed them into an interpolating scanner circuit (like this one: https://till.com/articles/scanner/ ) and from there you could control the output noise colour (and anything inbetween) with the wandering CV.
>> 
>> I wonder if the different noise colours all need to be derived from a single source for the crossfading to work.
>> 
>> Mike
>> 
>> 
>> On 2026-03-02 18:20, Thomas Hudson via Synth-diy wrote:
>>> I have an analog module that can generate blue, white, pink, and red (brownian) noise. I’m interested in how I might create a random walk using perhaps a sample/hold and smoothing function to produce a sort of wandering control voltage from each of these noise sources.
>>> I also was recently introduced to green noise. From Wikipedia:
>>> * The mid-frequency component of white noise, used in halftone
>>>   <https://en.wikipedia.org/wiki/Halftone>dithering
>>>   <https://en.wikipedia.org/wiki/Dithering>^[19]
>>>   <https://en.wikipedia.org/wiki/Blue_noise#cite_note-19>
>>> * Bounded Brownian noise
>>> * Vocal spectrum noise used for testing audio circuits^[20]
>>>   <https://en.wikipedia.org/wiki/Blue_noise#cite_note-comp.dsp_FAQ-20>
>>> * Joseph S. Wisniewski writes that "green noise" is marketed by
>>>   producers of ambient sound effects recordings as "the background
>>>   noise of the world". It simulates the spectra of natural settings,
>>>   without human-made noise. It is similar to pink noise, but has more
>>>   energy in the area of 500 Hz.
>>> Wondering how I might generate this other than using something like a bandpass filter tuned to 500 Hz using pink noise. I want to generate it in the analog realm.
>>> TIA,
>>> Thomas
>>> ________________________________________________________
>>> This is the Synth-diy mailing list
>>> Submit email to: Synth-diy@synth-diy.org
>>> View archive at: https://synth-diy.org/pipermail/synth-diy/
>>> Check your settings at: https://synth-diy.org/mailman/listinfo/synth-diy
>>> Selling or trading? Use marketplace@synth-diy.org
>> ________________________________________________________
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> 
> 
> ________________________________________________________
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Re: [sdiy] Various colors of noise.

2026-03-04 by Michael E Caloroso

Few people realize that the venerable Minimoog includes red noise. But it's a modulation source not audio. The front panel NOISE switch alternates between white and pink noise as an audio source, and also between pink and red noise as a modulation source. Red noise as a modulation source sounds like smoothed S&H.

MC

On Tue, Mar 3, 2026 at 6:14 PM Thomas Hudson via Synth-diy <synth-diy@synth-diy.org> wrote:
BTW, while researching creating green noise I came across a website for a Mac and iOS app:



In addition to noise colors, t also has beach sounds, fireplaces, babbling brooks, etc.

Fun little app.


On Mar 3, 2026, at 5:56 PM, Thomas Hudson via Synth-diy <synth-diy@synth-diy.org> wrote:

Interesting idea and article.

On Mar 3, 2026, at 4:58 PM, Mike Beauchamp <list@mikebeauchamp.com> wrote:

Hi Thomas,
Maybe take all of the different noises, and feed them into an interpolating scanner circuit (like this one: https://till.com/articles/scanner/ ) and from there you could control the output noise colour (and anything inbetween) with the wandering CV.

I wonder if the different noise colours all need to be derived from a single source for the crossfading to work.

Mike

Show quoted textHide quoted text

On 2026-03-02 18:20, Thomas Hudson via Synth-diy wrote:
I have an analog module that can generate blue, white, pink, and red (brownian) noise. I’m interested in how I might create a random walk using perhaps a sample/hold and smoothing function to produce a sort of wandering control voltage from each of these noise sources.
I also was recently introduced to green noise. From Wikipedia:
* The mid-frequency component of white noise, used in halftone
<https://en.wikipedia.org/wiki/Halftone>dithering
<https://en.wikipedia.org/wiki/Dithering>^[19]
<https://en.wikipedia.org/wiki/Blue_noise#cite_note-19>
* Bounded Brownian noise
* Vocal spectrum noise used for testing audio circuits^[20]
<https://en.wikipedia.org/wiki/Blue_noise#cite_note-comp.dsp_FAQ-20>
* Joseph S. Wisniewski writes that "green noise" is marketed by
producers of ambient sound effects recordings as "the background
noise of the world". It simulates the spectra of natural settings,
without human-made noise. It is similar to pink noise, but has more
energy in the area of 500 Hz.
Wondering how I might generate this other than using something like a bandpass filter tuned to 500 Hz using pink noise. I want to generate it in the analog realm.
TIA,
Thomas
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Re: [sdiy] Various colors of noise.

2026-03-04 by Tom Wiltshire

There's a similar heavily-filtered noise source ("infra-red" noise) in the Polyfusion synth schematics.

One problem with this way of generating this type of wandering modulation voltage is that the voltage level is heavily reduced on average, but adding gain to bring it back up is uncertain since the potential maxmium level isn't really decreased at all. E.g. if you add gain, it'll clip - not often, but probably sooner or later.

I've used cosine interpolation between random points to generate a similar waveform digitally. That avoids this issue, and has the advantage that you get some level of control over how fast the waveform changes too.

Tom
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> On 4 Mar 2026, at 04:19, Michael E Caloroso via Synth-diy <synth-diy@synth-diy.org> wrote:
> 
> Few people realize that the venerable Minimoog includes red noise.  But it's a modulation source not audio.  The front panel NOISE switch alternates between white and pink noise as an audio source, and also between pink and red noise as a modulation source.  Red noise as a modulation source sounds like smoothed S&H.
> 
> MC
> 
> On Tue, Mar 3, 2026 at 6:14 PM Thomas Hudson via Synth-diy <synth-diy@synth-diy.org <mailto:synth-diy@synth-diy.org>> wrote:
> BTW, while researching creating green noise I came across a website for a Mac and iOS app:
> 
> The original free color noise generator on the Internet. Hear what your mind has been missing…
> simplynoise.com
> <cropped-web_sn_appicon_512-1-180x180.png>
>  <https://simplynoise.com/>The original free color noise generator on the Internet. Hear what your mind has been missing… <https://simplynoise.com/>
> simplynoise.com <https://simplynoise.com/>	<cropped-web_sn_appicon_512-1-180x180.png> <https://simplynoise.com/>
> 
> In addition to noise colors, t also has beach sounds, fireplaces, babbling brooks, etc.
> 
> Fun little app.
> 
> 
>> On Mar 3, 2026, at 5:56 PM, Thomas Hudson via Synth-diy <synth-diy@synth-diy.org <mailto:synth-diy@synth-diy.org>> wrote:
>> 
>> Interesting idea and article. 
>> 
>>> On Mar 3, 2026, at 4:58 PM, Mike Beauchamp <list@mikebeauchamp.com <mailto:list@mikebeauchamp.com>> wrote:
>>> 
>>> Hi Thomas,
>>> Maybe take all of the different noises, and feed them into an interpolating scanner circuit (like this one: https://till.com/articles/scanner/ <https://till.com/articles/scanner/> ) and from there you could control the output noise colour (and anything inbetween) with the wandering CV.
>>> 
>>> I wonder if the different noise colours all need to be derived from a single source for the crossfading to work.
>>> 
>>> Mike
>>> 
>>> 
>>> On 2026-03-02 18:20, Thomas Hudson via Synth-diy wrote:
>>>> I have an analog module that can generate blue, white, pink, and red (brownian) noise. I’m interested in how I might create a random walk using perhaps a sample/hold and smoothing function to produce a sort of wandering control voltage from each of these noise sources.
>>>> I also was recently introduced to green noise. From Wikipedia:
>>>> * The mid-frequency component of white noise, used in halftone
>>>>   <https://en.wikipedia.org/wiki/Halftone <https://en.wikipedia.org/wiki/Halftone>>dithering
>>>>   <https://en.wikipedia.org/wiki/Dithering <https://en.wikipedia.org/wiki/Dithering>>^[19]
>>>>   <https://en.wikipedia.org/wiki/Blue_noise#cite_note-19 <https://en.wikipedia.org/wiki/Blue_noise#cite_note-19>>
>>>> * Bounded Brownian noise
>>>> * Vocal spectrum noise used for testing audio circuits^[20]
>>>>   <https://en.wikipedia.org/wiki/Blue_noise#cite_note-comp.dsp_FAQ-20 <https://en.wikipedia.org/wiki/Blue_noise#cite_note-comp.dsp_FAQ-20>>
>>>> * Joseph S. Wisniewski writes that "green noise" is marketed by
>>>>   producers of ambient sound effects recordings as "the background
>>>>   noise of the world". It simulates the spectra of natural settings,
>>>>   without human-made noise. It is similar to pink noise, but has more
>>>>   energy in the area of 500 Hz.
>>>> Wondering how I might generate this other than using something like a bandpass filter tuned to 500 Hz using pink noise. I want to generate it in the analog realm.
>>>> TIA,
>>>> Thomas
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>> 
>> 
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Re: [sdiy] Various colors of noise.

2026-03-05 by Donald Tillman

On Mar 3, 2026, at 1:58 PM, Mike Beauchamp <list@mikebeauchamp.com> wrote:
> 
> 
> Maybe take all of the different noises, and feed them into an interpolating scanner circuit (like this one: https://till.com/articles/scanner/ ) and from there you could control the output noise colour (and anything inbetween) with the wandering CV.

That interpolating scanner article is crazy!

> I wonder if the different noise colours all need to be derived from a single source for the crossfading to work.

Theoretically the opposite; a single noise source allows the possibility of phase cancellation between two different filter functions, while separate random sources guarantee no phase alignment.  That said, it's unlikely to be an issue.

Noise isn't my speciality, I'm usually trying to get rid of it, but I believe that...

A simple noise source, such as just generating a series of random values, should be "white noise", with a constant power level over any given bandwidth in Hz, regardless of frequency.  So the power content from 0 to 1KHz should be the same as 1KHz to 2Khz, and 2KHz to 3KHz, and so forth.

Our sense of hearing works over logarithmic frequency, per octave, so we expect a constant power level per octave.  That's called "pink noise".  

Starting with white noise, we need a low-pass filter that drops 3dB for each octave to make pink noise.  A half-integrator, if you will.  You can approximate it with a few low-pass shelf sections spaced out.

And the 3dB/Oct integrator was adopted as the way to go from one color of noise to another.  White to pink, pink to red, and so forth.  Or the other direction; white to blue.

So a noise generator with a continuous color control would basically involve a variable slope filter.  (Which is a pretty cool thing on its own, anyway; though more for mixing and regular instruments than synthesis.)

  -- Don
--
Donald Tillman, Palo Alto, California
https://till.com

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