# Audio phase cancellation

Hi,

I’m trying to do phase cancellation on some audio. Not sure which CHOP to use or how best to do it?

I am trying just using a math CHOP on the phase and inverting it but that is glitching the audio when i convert it back to audio domain.

Any thoughts?
phase.toe (22.4 KB)

In more detail what sound effect are you trying to achieve? Comb filters (delaying the signal, multiplying it, and adding to the original signal) achieve some kind of “phase cancellation” Feedforward Comb Filter Amplitude Response

Thanks. I am trying to do what phones do in that they feedback the signal to cancel out the echo of your own voice. I’m also just trying to figure out how to do the math in the best way on audio signals in Touch Designer. I feel like there should be a simple operation to cancel out the audio by inverting the phase? I have done this in Max/MSP. And yes, you can create comb filters, reverb, delays, etc. by doing these type of operations.

Hi again,
I figured it out. I was making it too complicated. Just need to use math on the original audio signal. No need to separate out the phase. See phase.toe attached here.
phase.toe (23.1 KB)

Suppose your audio is X. You’re doing X - (a*X) where a is between 0 and 1. This is the same as X*(1-a) which is basically the same as multiplying X by a number between 0 and 1. What I’m saying is the example you posted is not a typical example of phase cancellation because you’re just adjusting the volume of the input signal. However, if you were to delay one of the signals that leads to math4 by a few samples, then that would be a feed forward comb filter, which I believe is considered a kind of phase cancellation.

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