Different in noise. Can someone explain pls?

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Autobot
KVRian
718 posts since 27 Mar, 2013

Post Tue Mar 31, 2020 6:02 am

I'm aware of the different colors of nice like brown, pink, white, etc. noise but what exactly is Gaussian, F-F2-1/F2, Crackle, Dust, Bow, MM5837, LFClipNoise, Logistic, Lorenz-Rossler, Wave, etc. noise?

I found a Max4Live device (http://maxforlive.com/library/device/4588/fp-noise) with those different types of noise and wonder whats about. Can those type of noises reproduce with a synth like Zebra or similar.

Someone here to share knowledge? Thanks.
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BertKoor
KVRAF
11832 posts since 8 Mar, 2005 from Utrecht, Holland

Re: Different in noise. Can someone explain pls?

Post Tue Mar 31, 2020 6:22 am

Autobot wrote:
Tue Mar 31, 2020 6:02 am
I'm aware of the different colors of nice like brown, pink, white, etc. noise but what exactly is Gaussian, F-F2-1/F2, Crackle, Dust, Bow, MM5837, LFClipNoise, Logistic, Lorenz-Rossler, Wave, etc. noise?

I found a Max4Live device (http://maxforlive.com/library/device/4588/fp-noise) with those different types of noise and wonder whats about.
You could do some googling and find:
https://en.wikipedia.org/wiki/Gaussian_noise
https://www.musicdsp.org/en/latest/Synt ... ators.html
http://synton.nl/wp-content/uploads/2017/04/mm5837.pdf

So most of these types are about the calculational model used to generate it. Just run it and take a look at the spectrum it generates.

Autobot wrote:
Tue Mar 31, 2020 6:02 am
Can those type of noises reproduce with a synth like Zebra or similar.
u-he Zebra product page wrote: The Noise module features four different flavours: White, Pink, Digital, and Crackles - which produces sounds simlar to a Geiger counter
So that's "no, not directly"
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Autobot
KVRian
718 posts since 27 Mar, 2013

Re: Different in noise. Can someone explain pls?

Post Tue Mar 31, 2020 6:26 am

Thanks. I used google but since I'm not a scientist the explanations did not brought me further :-) I would be more interested in the sound of the different noises. As I said I'm familiar with different colors of noise and their sound but how does sound MM5837 noise? As far as I understand the MM5837 is a chip for generating pink/white noise. So whats the difference in terms of sound?

Edit: maybe I buy the m4l device to test the sounds by myself. although for the 3€ I could buy groceries for a little dinner. Yes! I'm tight on money... :oops:
Last edited by Autobot on Tue Mar 31, 2020 6:29 am, edited 1 time in total.
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Autobot
KVRian
718 posts since 27 Mar, 2013

Re: Different in noise. Can someone explain pls?

Post Tue Mar 31, 2020 6:28 am

sorry. double post. :roll:
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andro_b
KVRer
5 posts since 21 Feb, 2020

Re: Different in noise. Can someone explain pls?

Post Fri May 15, 2020 11:22 pm

Take a look at Dr. Stéphane Pigeon's page of audio tests, in particular here:

https://www.audiocheck.net/testtones_index.php

He gives some subjective impressions and perceptions of what different 'colours' of noise sound like, and an explanation of each term.

It is indeed a mathematical subject, but the above has good verbal descriptions, and sound samples.

Things like crackle and dust are not mathematical noises, but usually based on csound generators which model those phenomena, using algorithms to emulate such things. Various synths have varying numbers of different types of noise, but usually white and pink at a minumum. If you want lots of noise generators, the software (and hardware) modular synths have hundreds of noise modules available.

mystran
KVRAF
5651 posts since 12 Feb, 2006 from Helsinki, Finland

Re: Different in noise. Can someone explain pls?

Post Sat May 16, 2020 10:55 pm

andro_b wrote:
Fri May 15, 2020 11:22 pm
Things like crackle and dust are not mathematical noises, but usually based on csound generators which model those phenomena, using algorithms to emulate such things.
It is also possible to imlement such thing as simple samples, looped and started from a random position (just make them long enough that the repeat isn't obvious), or you could even do some sort of granular synthesis for them. This way you can easily have "noise generators" that produce sounds that are tricky and/or expensive to model properly.

Another classic approach to generating "standard" noise with arbitrary spectrum is to take a long FFT window (eg. at least 10-15 seconds), fill the magnitudes with whatever spectrum you want, randomize the phases and then IFFT the thing to get a perfectly looped sample.
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Music Engineer
KVRAF
3834 posts since 8 Mar, 2004 from Berlin, Germany

Re: Different in noise. Can someone explain pls?

Post Sat May 23, 2020 8:21 am

if you read something like "gaussian", this refers to the probability density distribution of the noise - that is the relative number of samples that fall in a given range of amplitude values. the most basic noise generators will give you a uniform distribution of the amplitude values. to see this, you want to look at the histogram. for uniform noise, it looks like this:
NoiseUniform.png

every amplitude value is equally likely to occur. if you add the output of two such uniform noise generators (and divide by two), you get a triangular distribution like this:

NoiseTriangular.png

and if you add the output of three (and divide by 3), you get this:

NoiseQuadratic.png

this is actually a piecewise parabolic curve. if you add n noise generators, the theoretic shape is the convolution of n rectangular functions which gives you a piecewise (n-1)-th order polynomial. the next one would be piecewise cubic, etc. and the shapes become more and more gaussian'ish, the more noise-generators you add. this is called the Irwin-Hall distribution. note that all these noises are spectrally white - and also sound more or less the same to me (although, of course, the uniform is loudest because it has the highest amount of high-amplitude values) but the distribution of amplitude values may likely have effects on nonlinear processors further down the signal chain (just a hunch - i did not yet explore this very much).
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Music Engineer
KVRAF
3834 posts since 8 Mar, 2004 from Berlin, Germany

Re: Different in noise. Can someone explain pls?

Post Sat May 23, 2020 8:41 am

just a few days ago, i played around a little bit with combining basic noise generators. here is an example of some sort of crackly noise (i needed to zip it because the forum does not support wavefile attachments):
NoiseTriModal7.zip
what i did here was the following: use three irwin-hall generators (of order 7) with different centers (one in the middle, i.e. mean=0, one with negative and one with positive mean), use another noise generator to select, per sample, which one of the three to use for the current sample. the selector generator is lowpassed in order to make it more likely to select the same from the 3 for successive samples. the result is some sort of crackle. this noise has the following distribution:
NoiseTriModal.png
it has 3 maxima, which is why i called it trimodal. but the histogram does not tell you the full story - i could create noises with the same distribution without the lowpass on the selector but they would sound totally different - the crackle would be gone. note also that the frequency spectrum also doesn't really tell you very much here - it looks almost white, too with a slight boost of lower frequencies. i wonder which sort of plot would reveal the features of this sort of noise. maybe some sort of histogram that shows the conditional probability of amplitude values, conditioned on what the previous value was - or something. i guess, if one likes noises, one can have a lot of fun by combining noise generators in various ways
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Music Engineer
KVRAF
3834 posts since 8 Mar, 2004 from Berlin, Germany

Re: Different in noise. Can someone explain pls?

Post Sat May 23, 2020 9:48 am

lorenz and rössler systems are a totally different thing. they are based on chaotic systems of differential equations:

https://en.wikipedia.org/wiki/Lorenz_system
https://en.wikipedia.org/wiki/R%C3%B6ssler_attractor

lorenz sounds like this:
LorenzX.zip
maybe not totally useless. physics is full of such chaotic systems. might be fun to explore. i didn't do rössler yet, but i can serve with double-pendulum instead:
DoublePendulumM1_2.zip
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BlitBit
KVRist
320 posts since 28 Nov, 2013 from Germany

Re: Different in noise. Can someone explain pls?

Post Sat May 23, 2020 12:47 pm

Music Engineer wrote:
Sat May 23, 2020 8:21 am
every amplitude value is equally likely to occur. if you add the output of two such uniform noise generators (and divide by two), you get a triangular distribution like this:

NoiseTriangular.png
First of all, thanks for this great visual explanation! Do I understand correctly that this basically means: If you take two white noise sources and mix and normalize them then it will be more likely that two mixed samples will cancel out than that they result in a "large" value?
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Music Engineer
KVRAF
3834 posts since 8 Mar, 2004 from Berlin, Germany

Re: Different in noise. Can someone explain pls?

Post Sat May 23, 2020 2:01 pm

If you take two white noise sources and mix and normalize them then it will be more likely that two mixed samples will cancel out than that they result in a "large" value?
yes, indeed.
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