All helicopters in the Army's inventory produce noise levels in excess of established guidelines for safe limits. Much time and effort, and many funds, have been expended to control and reduce noise to levels that are safe for the aviator. Active noise reduction (ANR) is a technique that measures the noise in the earcup enclosure and produces a signal that is out of phase. Then the signal noise is reintroduced into the earcup through the earphone element as a pressure signal that cancels the noise originally measured.