Investigation of aircrew noise exposure levels and hearing protection solutions in helicopter cabin

High noise levels in the helicopter cabin adversely affect aircrew communication and reduce comfort in the short-term and may lead to hearing loss in the long-term if flight helmets cannot provide sufficient protection to the aircrew. A cabin noise exposure survey has been performed on a Royal Canadian Air Force CH-147F Chinook heavy lift helicopter to evaluate the noise environment and noise protection performance of the flight helmet. Investigation results showed that the low-frequency noise attenuation provided by the Royal Canadian Air Force flight helmet was marginal in high-speed flight conditions that generate loud cabin noise. Therefore, in-canal earphone integrated with active noise cancellation capability was investigated to provide enhanced noise protection and improve clarity in voice communication. Simulation and proof-of-concept test results verified that active noise cancellation in-canal earphones can serve as a feasible technical solution to provide enhanced noise attenuation to mitigate the low-frequency N/rev tonal noise generated by the aerodynamic pressure from the helicopter rotor blades.