Research On The Analysis Method Of Aircraft Airworthiness Flyover Noise Signal

In current aircraft noise research,1/3 octave data is mainly used for noise prediction and research,but it is difficult to calculate the impact of aircraft's variable speed movement on the ground noise measurement point on the noise signal accurately,including compression and expansion of the noise signal and Doppler frequency shift.Through the study of theoretical methods of noise calculation from the analysis method of aircraft flyover noise signal and the propagation distance and propagation time of noise signals which spread in a medium where the sound velocity distribution changes linearly,simulate the original noise signal generated by the engine during takeoff and flyover,and through the acoustic line method to calculate the noise signal received by ground noise measurement point.In this way,we can study and analysis the time-domain noise signal received by the ground noise measurement point during the aircraft takeoff and flyover.Based on various reference data of the EMB190 aircraft during takeoff and flyover provided by ANP database,calculate the track data of this type of aircraft takeoff for a certain time.Use the noise 1/3 octave data of the same series of engines of the aircraft in ground static noise test,the 1/3 octave data of different angles with the engine axis at a certain speed during flight is obtained after correction of the aircraft flight,and calculate the maximum sound pressure value of the engine noise time-domain signal at different angles with the engine axis during flight.Use this sound pressure data and 1/3 octave data which is obtained after correction of the aircraft flight to simulate the time-domain signal of the original noise produced by the engine during takeoff.Calculate the noise time-domain signal received by ground noise measurement point using the theoretical methods for noise calculation during aircraft flyover and sound propagation theory formula every 0.5 second,compute the instantaneous sound pressure level in 24 1/3 octaves of the noise time-domain signal every 0.5 second,and calculate effective perceived noise level of the engine during the aircraft flyover noise measurement according to the regulations of CCAR-36.At the same time,study the impact of the received noise signal when the aircraft moves relative to the groun d noise measurement point using noise time-domain signal which is calculated.The results show that when the aircraft approach or move away from ground noise measurement points,the noise signal received by the ground noise measurement point will be compressed or expanded,and the frequency will increase or decrease resulting in frequency shift.The results calculated by the Doppler shift equation verify the correctness of the frequency shift.Provide some references for noise prediction and research using time-domain noise signal.