It works like ANC, which is inputting the same noise at an alternating frequency cancelling the original noise out (they use microphones to pick up the noise.

So in this case they use an alternating frequency to cancel out each other's noise leaving just the main audio package. So twice as much noise generated but it eliminated itself. The result is basically an emi shielded signal. Huge over simplification, probably using the wrong wording, and my interpretation of the science is probably a bit wrong. But yeah the two separate signals eliminate each other's noise.