The Analysis Of The Environmental Impact Of The C919 Aircraft Noise

The large-scale civilian passenger aircraft C919 was researched and manufactured by China independently and the noise airworthiness certification must be carried out before the formal operation.Chinese noise airworthiness certification standards have some corresponding provisions for the measurement method and limited value of lateral noise.Therefore,the lateral attenuation is an important part of lateral noise prediction,and it is necessary to study its algorithm.Based on the study of noise airworthiness certification for large jet aircraft and the basic theory of sideline attenuation,the principle and advantages and disadvantages of the lateral attenuation algorithm introduced by the International Society of Automotive Engineers and International Engineering Science Data Unit are analyzed.Based on the measurement noise data in the ANP database,the lateral attenuation algorithm is studied and analyzed.The noise database for jet aircraft is established and the lateral attenuation curves corresponding to the 24 center frequencies of 1/3 octave are drawn,which can be the reference for the sideline noise prediction and noise airworthiness certification of C919 aircraft.Based on the measured sound pressure level data in the ANP database,the calculation process of the lateral attenuation algorithm and the correction method of the measurement data are described in detail.Combined with the flight path calculated by the similar model aircraft of C919,the lateral attenuation values of different elevation angles,propagation distances and frequencies are calculated.The variety of the lateral attenuation with these three parameters is obtained,and the influence factors of the lateral attenuation are analyzed according to the lateral attenuation curves.At the same time,the measured noise data of A320 which is similar to C919 is used to optimize the single plane noise contours according to the lateral attenuation algorithm and database.The application of lateral attenuation algorithm when used to calculate the single airplane noise level is researched.Finally,according to the algorithm of lateral attenuation,the attenuation values of different elevation angles and propagation distances are calculated for 24 center frequencies.The lateral attenuation database and the curves for all jet airplanes is established and drawn by the software.The results show that the lateral attenuation algorithm is suitable for all jet aircraft.The database established in this paper can be used to predict the lateral noise of the jet aircraft whose engines are installed under the wing,which can provide reference for the noise airworthiness certification of C919 aircraft.