How does M-DEX's FreeFocus work?
The left and right focus works by setting the microphone mode on the focus side to omni-directional and engaging an effective noise reduction scheme on the opposite side.  FreeFocus utilizes the natural head shadow effect, which can be as much as 20dB in the mid to high frequencies, to increase effectiveness. The amount of reduction on the opposite side will depend on the sound environment. The left and right focus will be more effective when the source is close to the hearing aid user than when the source is far away.  The front/back focus takes advantage of the directional microphones which are set to fixed directional in the forward mode and are inverted in the backward mode.