The active noise-reducing headset is one of the most successful applications of active control of sound. This paper provides a technical review of the headset, giving examples of applications in which it is most successfully used. The principles of passive noise attenuation are presented and active attenuation is introduced, showing how the two complement attenuation performance. Both analogue and digital implementations of the headset control system are described, including combination of analogue and digital controllers into a single system. The paper concludes with a view into the future where new technologies open up possibilities for improving headset performance in more challenging environments.