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Calculate the phase cancellation of 2 signal
Old 17th October 2009
Gear Head
gerhardroux's Avatar

Thread Starter
Calculate the phase cancellation of 2 signal

Dear All

I'm trying to calculate (and plot) the audio information that is lost with the combination of two signals, more specific two microphones on a snare drum. According to my limited knowledge I can calculate the difference of two summed channels as follows:

Signal A + Signal B = Signal C
Signal A (Reversed polarity) + Signal B = Signal D

Signal C (Reversed polarity) + Signal D = DIFFERENCE

Now I have the difference between two signals. I would like to calculate what exactly what one is losing in both instances (straight or inverted polarity summation of A + B), but can't figure it out. I suspect that an answer might be found by reintroducing the calculated difference to the original signals.

Any guidance would be greatly appreciated.

Gerhard Roux
Old 20th October 2009
Lives for gear
Les's Avatar

Hmm...well, you have

D-C=B-A-A-B= -2A

Of course two mics on a snare will have delay effects that result in complex comb filter response.

Not sure what you're getting at.
Is that what you wanted to know?
Old 20th October 2009
Gear Head
gerhardroux's Avatar

Thread Starter
Thank you Les, I'm getting closer. I also suspect that the arc tangent of the ratio of amplitudes will give a vector that can be used. I'm going to visit my parents over the weekend and will ask my mother to solve my problem for me. (True).
Old 20th October 2009
Lives for gear
dcollins's Avatar

Verified Member
Old 20th October 2009
Gear Head
gerhardroux's Avatar

Thread Starter
Thanks Dave! This helps a lot. This formula is a good starting point, I think it will be possible to replace the angular displacement of the sine wave with a more complex pattern. Wish I was smarter....
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