Cockpit Noise And Speech Interference Between Crewmembers PDF Download

Active Noise Reduction (ANR) is a new technology which can reduce the level of aircraft cockpit noise that reaches the pilot's ear while simultaneously improving the signal-to-noise ratio for voice communications and other information-bearing sound signals in the cockpit. A miniature, ear-cup mounted ANR system, developed by Royal Aerospace Establishment, Farnborough, United Kingdom, was tested by U.S. Army Aeroflightdynamics Directorate, Simulation and Aircraft Systems Division, Crew Station Research and Development Branch to determine whether speech intelligibility is better for helicopter pilots using ANR compared to a control condition of ANR turned off. The ANR system was installed in a stock Army SPH-4 flight helmet, and tested in a background of recorded AH-1S (Cobra) cockpit noise, using phonetically balanced word lists, per MIL-STD-1472C. Two signal-to-noise ratios (S/N), representative of actual cockpit conditions, were used: 0 dB and +10 dB for the ratio of the speech to cockpit noise sound pressure levels. Speech intelligibility was significantly better with ANR compared to no ANR for both S/N conditions. Variability of speech intelligibility among pilots was also significantly less with ANR. When the stock helmet was used with ANR turned off, the average PB word speech intelligibility score was below the Normally Acceptable level, per MIl-STD-1472C in the 0 dB S/N levels and exceeded the Exceptionally High Intelligibility level with S/N +10 dB. Keywords: Cockpit communications, Active noise reduction.