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Old 12-04-2020, 06:21 PM   #1
TonE
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Default How to subtract from audio A another audio B?

Which is best way of subtracting from first audio A, a second audio B?

We all know a mixer, or a track in reaper does the adding: A + B
But I would like to do: A - B

Is this possible? If yes, how?

Why I want this?
For analysis purposes, mixing analysis for example, doing from any audio: audio - pink noise, then looking at the result, meaning analysing only this output for comparison purposes.
Take 100 mixes. Do from each x - pink_noise, then see what is similar or different in those.

Did anyone do this already. What would one expect? Interesting idea. Nonsense? Thanks for reading thus far. Have a nice day my friend.
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Old 12-04-2020, 06:24 PM   #2
domzy
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i'm possibly misunderstanding you, but can't you just reverse the phase on audio B and then add it to audio A?
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Old 12-04-2020, 06:37 PM   #3
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Domzy got it. You do need to fiddle with the level of one of tge source tracks, looking for minimum output.
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Old 12-04-2020, 08:37 PM   #4
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It ain’t gonna work via polarity flip with the pink noise. The pink noise is only accidentally correlated to the audio, and inverting the pink noise will just be adding inverted pink noise. You might be able to get...something...with an FFT-type thing. Maybe ReaFIR in subtract mode with pink noise as the noise print? But that will probably add all kinds of “ghost birds” artifacts and tell you more about the limitations of that kind of processing than the audio you’re trying to analyze.

Honestly, you’ll probably get more mileage out of a good spectrum analyzer like SPAN. If you set the slope to -3db/octave, pink noise will be a flat horizontal line, so the ways that the signal deviates from that straight line are the ways that they are different from pink noise. SPAN at least has a couple of ways of comparing two signals directly.
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Old 12-04-2020, 10:18 PM   #5
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There's an interesting technique where you start with grey noise (acoustic spectrum) only and raise the levels of all the individual tracks up until you can just barely hear them, then you EQ until you can hear them with a natural tone, then you take the noise away. I've tried it a few times, it's a good starting point I guess.
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Old 12-04-2020, 11:31 PM   #6
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I know the results are a bit rough but might Spleeter work?


W
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Old 12-04-2020, 11:47 PM   #7
mschnell
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Quote:
Originally Posted by TonE View Post
But I would like to do: A - B
What are you trying to accomplish with that ?

-Michael
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Old 12-05-2020, 09:33 PM   #8
Philbo King
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Quote:
Originally Posted by Fergler View Post
There's an interesting technique where you start with grey noise (acoustic spectrum) only and raise the levels of all the individual tracks up until you can just barely hear them, then you EQ until you can hear them with a natural tone, then you take the noise away. I've tried it a few times, it's a good starting point I guess.
I've used this in the past for mixing. It works pretty well to get a balance when you just barely hear each part with noise present.

Ash is correct about trying to subtract pink noise from music, or music from pink noise. It justs inserts the noise into the result.
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Old 12-06-2020, 03:28 AM   #9
jrk
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I've got some paint that needs un-mixing.
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Old 12-06-2020, 03:44 AM   #10
androo
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Audacity has a noise removal tool. You sample a section of your source noise and it will do magic and remove it. Don't know if it can un-mix paint but haven't been willing to pour paint on my PC to find out.
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Old 12-06-2020, 03:50 AM   #11
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you can check out some spectral processes do get some of those effects, depending on what your after. There's not a lot of realtime vst's that will allow subtraction of 2 signals, though the Little Endian Spectrumworx has a bunch in the ?PVOC section

I've thought it would be pretty cool for some scripts using the spectral peaks to do various effects like that on wave files lol.

other than CDP though, and a few other tools, I can't think of much that will do those effects within reaper atm

edit/ doesn't fft do phase cancellation, but uses bins for certain frequency ranges? just thinking that you need to be in the frequency domain if you want to do those types of processes on a range of frequencies??...i dunno lol,
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