Landing gear noise identification in the ARJ21 aircraft landing process

The acoustic flyover tests are performed for an ARJ21 aircraft with the objective to measure the landing gear noise.The algorithms of improved frequency domain Conventional Beamforming(CBF) and Deconvolution Approach for the Mapping of Acoustic Sources(DAMAS) are used.It is demonstrated that DAMAS has better capability of noise source identification.In order to improve the utilization of the microphones,a multi-arms spiral array is designed and applied to the measurement.The doppler effect is removed by using linear interpolation.According to the distribution of the main landing gear and nose landing gear,the identification area is divided into two parts and is analyzed from 140 Hz to 800 Hz on 1/3 octave band.It is shown that the main landing gear is the main noise source above 250 Hz. Especially,it is the only strong noise source in 1/3 octave band of 500 Hz centre frequency,whereas the nose landing gear is the main noise source in 1/3 octave band of 630 Hz centre frequency.By this test,the noise characteristics of the main landing gear and nose landing gear are investigated in different frequency range which is significant to landing gear noise control engineering.