Abstract:
High noise levels in the helicopter cabin affect aircrew communication and reduce aircrew comfort, and may lead to hearing loss in the long-term if flight helmets cannot provide sufficient protection to the aircrew, or are improperly fitted. A cabin noise exposure survey has been performed on a Royal Canadian Air Force (RCAF) CH-147F Chinook heavy lift helicopter to evaluate the noise environment. The insertion loss performance of the flight helmet was characterized in a reverberant acoustic chamber facility. Investigation results showed that the low frequency noise attenuation provided by the RCAF flight helmet was marginal at high speed flight conditions in which significant cabin noise levels existed in the helicopter cabin. To enhance the low frequency hearing protection performance and clarity in voice communication, in-canal Communication Ear Plugs (CEPs) integrated with active noise cancellation (ANC) capability was investigated. Simulation and proof-of-concept test results demonstrated that the ANC in-canal CEPs 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.