How can you subtract .wav waveforms?

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-- How can you subtract .wav waveforms?

Posted by trisk on Jan-08-2009 22:12:

How can you subtract .wav waveforms?

I'm looking to figure out how to subtract one audio file's waveform from another's.

This is in attempt to reverse the process of combining both audio channels to eliminate any inverses of waves between the two. I want to hear the part that actually gets eliminated, so I figured that subtracting the combined one from the original would give such effect.

I've been searching for a while, and I can't find how to do it, I would appreciate any help on this topic. Thanks!

Posted by echosystm on Jan-08-2009 22:59:

you're not being very clear.

if you reverse the phase of waveform A, against waveform B, you will hear everything that is in B, but not in A (and vice versa). "I want to hear what is being eliminated" - that would simply be waveform A, in its unmodified form, lol...

Posted by Zak McKracken on Jan-09-2009 00:20:

sounds like u will have to learn some of the basics in radio technology, FM and AM. i dont know it tho but it might be described somewhere in those context. have no idea if its really possible, i just assume that for this to be possible you will have to delay each frequency of the signal by 90degress (or 180? im not that good at these math things?) i dont know tho im just guessing

Posted by kitphillips on Jan-09-2009 03:03:

I love it when people use complicated terms and only make it harder to understand.

So I think what your trying to do is get a track, phase invert one of the stems of that track and be left with the original track only without the stem you have? you need some sort of phase inverting tool, almost every DAW has one. Make sure the stem you have is an exact copy of the stem in the track.

Posted by trisk on Jan-09-2009 03:19:

quote:
Originally posted by kitphillips
I love it when people use complicated terms and only make it harder to understand.

So I think what your trying to do is get a track, phase invert one of the stems of that track and be left with the original track only without the stem you have? you need some sort of phase inverting tool, almost every DAW has one. Make sure the stem you have is an exact copy of the stem in the track.

Precisely,

here is an example.
This clip plays the original for first 10 seconds, then the same thing but the phase invert for the next 10 seconds. What I would like is the part that is heard in the original, but not in the invert.

[[ LINK REMOVED ]]

Posted by mzvirbulis on Jan-09-2009 05:01:

All you are talking about is MS decoding which is the way stereo works!

So what you listening to there is the side band channel, this is the signal that is not common on both speakers (L+R)or mono.

Posted by mzvirbulis on Jan-09-2009 05:09:

So all you need to do is Convert to mono on the original, dont worry about using the other sample! Because what u want to hear is everything panned centre, hence the bass etc. And everything in the side channel gets cancelled.

Posted by Stef on Jan-09-2009 05:38:

quote:
Originally posted by echosystm
you're not being very clear.

Indeed. If you are using FL studio, i know there used to be a bundled fx plugin called phase inverter.

Posted by MaxC on Jan-10-2009 02:35:

Just download Voxengo's free MSED VST. Load it up in your VST host of choice and lower the volume knob on the "Mid" channel all the way. What you will be left with is the sound the disappears when playing back in mono .

Posted by trisk on Jan-10-2009 15:46:

Thank you everyone very much for your help. I have now achieved it!

I'm hearing more in the mid track than i though i would because a lot seems to be carried through from the side tracks