In the area of active noise cancellation headsets, the noisy environment often encountered in the link with communication systems causes lack of intelligibility on the outward communications path. Consequently another in-wire cancellation channel to enhance the intelligibility is required. This additional processing channel adds to the cost of the headset. The invention uses residual microphones (12) to reproduce the sound that remains in the ear after cancellation so that the controller (13) can make further adjustments through filter (15) and LMS adapter (14) to the anti-noise signal.