Evaluation of Aircrew Noise Exposure Levels on a Canadian CH-147F Chinook Helicopter

The cabin and cockpit noise levels of a Royal Canadian Air Force CH-147F Chinook medium to heavy lift utility helicopter were evaluated in this study. The sound pressure levels were measured at nine aircrew locations through 43 unique and representative flight and ground conditions in accordance with the ISO 5129:2001 standard. Additionally, the performance of a combination of currently in service helmets and headsets were evaluated in accordance with the ANSI Standard S12.42. The hearing protection performance results were used in combination with the measured sound pressure levels to evaluate the performance of the hearing protection in the context of the CH-147F noise environment. Results showed that the David Clark headsets equipped with active noise reduction provided the most superior hearing protection. The maximum exposure limit duration was calculated for each microphone location, hearing protector performance and flight condition combination. It was found that the David Clark headsets provided sufficient protection for an unlimited duration of exposure for an individual with a properly fitted headset. It was also found that improperly fitted hearing protection could result in an increased risk of hearing damage after merely 18 seconds.