An Active Noise Reduction System for AIrcrew Helmets-Flight Trials in Strike AIrcraft

INT RODUCT IONAn active noise reduction system (ANR) has been developed for use in aircrew helmets. in which the acoustic noise field inside the ear defender is detected using a miniature microphone, and an antiphase signal is fed back to a communications telephone within the ear defender.The objectives for this development have been to improve speech intelligibility, and to reduce noise exposure.Developed under contract to the Ministry of Defence (Procurement Executive), by the University of Southampton.the ANR system has been comprehensively tested in a series of laboaratory trials (1), followed by flight trials in a number of aircraft.'In order to eliminate user controls, an adaptive control facility has recently ' been added, which optimises the degree of noise cancellation to compensate for variations in helmet fit between wearers.