The Assessment of Sound Attenuation and Speech Intelligibility of Selected Active Noise Reduction Devices and the Communications Earplug When Used with the HGU-56/P Aviator Helmet

Abstract : The Program Manager for Aircrew Integrated Systems (PM-ACIS), formerly Aviation Life Support Equipment (PM-ALSE), requested the U.S. Army Aeromedical Research Laboratory (USAARL) examine the status of active noise reduction (ANR) systems available in the marketplace. The mechanism for acquiring the devices was a Cooperative Research and Development Agreement (ORDA) which was implemented with three U.S. corporations. Each corporation agreed to modify three HGU-56 aviator helmets, furnished by the Government, by installing their ANR system. The modified helmets, the communications earplug (CEP), and the standard HGU-56 helmet were evaluated by the USAARL Aircrew Protection Division to determine the electro-acoustic, hearing protective, and speech intelligibility characteristics. Standard techniques, using human subjects for sound attenuation and speech intelligibility, were used to complete the measurements.