Objective To propose recommendations for noise protection and control measures in high-performance fighter cockpits by investigating the noise exposure of pilots in cockpits.Methods In the ground test for 3 types of high-performance fighters(J-A,J-B and J-C),the total sound pressure level(SPL),A sound level,as well as the linear SPL at 31.5,63,125,250,500,1 000,2 000,4 000,8 000 Hz were respectively measured by the sound level meter installed at ear position of a dummy pilot in cockpit and at 2.5 m away along the line started at right tail nozzle and 60° off the aircraft longitudinal axis when the engine accelerated to its maximum speed for 5-180 s.Ten young male volunteers with normal hearing were selected to use 125,250,500,1 000,2 000,4 000,8 000 Hz octave center frequency narrowband signals,respectively,to test their hearing thresholds with and without 3 types of flight helmet(imported,in-service,and newly developed)under active and passive noise reduction conditions.The sound attenuation values of the helmets(difference between the bare-ear threshold and the threshold with the helmet)were calculated.Results The total SPL at the ear position of the dummy pilot in the cockpits of J-A,J-B,and J-C during ground test at maximum engine operation was 102.2,100.4,111.2 dB,respectively;the total SPL at the tail nozzle of J-B and J-C was 134.4,148.0 dB,respectively.The cockpit noise of J-C exceeded the limit standard of GJB 565A—2009.Except for the measure at 4 000 Hz,the sound attenuation values of different helmets at other frequencies were significantly different(H=35.49,38.93,32.37,33.50,23.96,27.81,all P<0.001).By attenuating under active state of Type B helmet,the total noise exposure SPL in the cockpits of J-A,J-B,and J-C was 87.3,84.1,89.3 dB,respectively.Conclusions The noise in high performance aircraft cockpit still exposes pilot in relatively high SPL.It still poses the potential threat to pilot's hearing health and performance.Helmet noise attenuation needs further development.The active attenuation of helmet,as well as the reduction of the source noise level is still the main goal of noise protection.
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