Motorolas new and improved noise cancelling technique uses two microphones to more efficiently filter the users voice. Se the video for a demonstration.
Motorola Industrial Noise Cancelling (INC) RSMs are equipped with one "ordinary" microphone directed towards the user and one directed away from the user, i.e. the surroundings. Audio is recorded on both microphones and is then compared. Very simply put, the audio that differs between the two recordings is the data that gets transmitted to the recipient and reproduced in the speaker.