Active Noise Reduction

Recently, headset manufacturers began producing headsets featuring ANR. ANR works because noise becomes "anti-noise" when its phase is inverted 180 degrees. Noise and anti-noise together cancel each other out. Using tiny microphones located near the wearer's ears, ANR headsets sense the background low frequency noise experienced by the pilot. The headsets then develop an anti-noise signal and play this anti-noise signal through separate speakers in the headset. The noise and anti-noise are heard by the pilot at the same time. Since the two sounds cancel each other out, the pilot cannot hear either one. The result is astonishing for those who have never experienced an ANR headset. The noise is not reduced, not muffled, not dimmed; it is gone. Pilots who use ANR headsets report reduced levels of fatigue, and fewer headaches while flying. Pilots also report that ANR headsets allow them to operate radio volume at a lower level than previously needed, reducing potential hearing damage from high radio volume levels.

Headset manufacturers originally targeted the new ANR headsets at General Aviation. Since many General Aviation aircraft produce high levels of noise in all frequencies, ANR features were merely added to existing passive noise reduction (PNR) headsets. That meant that all first generation ANR headsets were of the "ear defender" type, a type unsuitable for airline use.

Four manufacturers, Bose, Pilot Avionics, Telex, and Sennheiser produce light-weight ANR headsets suitable for use in airline cockpits. Headsets are produced in two models, a lightweight closed ear cup model, and an even lighter open ear "supra aural" model.