Performance of Hearing Protectors in Ejection Seat Parachute Gun Firing

During ejection rescue, the parachute gun attached to a rocket-assisted ejection seat generates jet noise that may damage a pilot’s sensitive auditory organs; hence the effectiveness of hearing protectors, primarily a helmet and earmuffs, is evaluated. A parachute gun firing experiment is designed, and overpressure data with and without protection are measured simultaneously during firing using piezoelectric pressure sensors inside and outside dummy ears. A comparative study of the measured data is conducted using time domain analysis and wavelet transformation methods, and the results show that the jet noise generated by a parachute gun firing is a broadband signal, consisting of shock waves and impulse noise; different from the attenuation characteristics in the continuous noise environment, in the jet noise environment, the effect of hearing protectors is significant for extenuating the high-frequency components that are prone to injury, but not significant for extenuating the low-frequency components.