The frictional noise of air conditioning rotor compressors mainly comes from the internal contact pairs.In order to identify the source of frictional noise,the friction coefficient of different friction pairs in the system composed of crankshaft and upper and lower flanges were measured firstly,and the negative friction-velocity slope curves were fitted.The finite element model of the crankshaft flange system was established.By loading the negative friction-velocity slope curves,the complex eigenvalue and equivalent damping ratio were extracted,and the possible frequency of friction noise was preliminarily analyzed.Then,EMD-FastICA analysis was carried out on the actually collected compressor noise signal,and the frequency of frictional noise was extracted to confirm the preliminary conjecture.In order to predict the trend of frictional noise,the sliding friction coefficient and static friction coefficient were adjusted to load the crankshaft flange model with different negative friction-velocity slope curves,the influence of friction coefficient on the frictional noise was analyzed.The results show that in the crankshaft flange system,the friction noise comes from the friction self-excited vibration between the thrust surface of the lower thrust part of the crankshaft and the upper face of the lower flange.For the thrust surface lower flange kinematic pair,reducing the static friction coefficient and sliding friction coefficient in the negative friction-velocity slope can help to suppress the generation of friction noise.