A fast and accurate numerical method is presented for predicting the sound field generated by subsonic propellers.The free space field

including the near and far sound field radiated by noncompact sources

is calculated by means of a retarded time integration in time domain.The FW H equation is applied to solving the sound field generated by moving boundaries of solid body in the flow field

but its quadrupole term is neglected

thus the noncompact sources mean the thickness source and the load source both included in the dipole term.According to the assumption

the sound field generated by a 3 D shaped propeller is considered as the sum of the terms radiated by each strip element located spanwise.The pressure chordwise distribution at each element should be known before solving the sound field.For this purpose a code solving 2 D compressible full velocity potential equation with body fitting coordinates is used which has been developed by BUAA previously.Comparison of calculated results with test data proves the present method and the code to be useful engineering tools.This conclusion has been also testified in the design of a propeller.