I think this is a bit complicated, since the IT is quite a way away from your ears. So the noise recieved by the Microphone would be different from the one recieved by your ears.
You have to match the frequency pretty well and time everything right, if you are off by even 1/4 of the period you can actually increase the noise. so for a standard background noise of 200 hz (Figure pulled right out of thin air) you would have to time everything right down to 0.00125 seconds.

But now i'm interessted in using a 2 Mic Setup to test how much difference this would make in a practical application.

This sounds like an interessting project.