An aeroacoustical modification of a propeller is considered with the aim of great enhancement of its takeoff efficioncy and appropriate cutdown of its noise level when its blade number

blade hub and cruise efficiency are kept unchanged.A time domain method is applied to predicting near and far the sound field.From iterative aeroacoustical and aerodynamical optimization an optimum design scheme has been obtained.And two 1/3 scaled model propellers were made to simulate the original and modified propellers respectively.The results of comparative ground experiments show that the OASPL(Overall Sound Pressure Level)decreases by 1 to 1 5 dB while other technical spesifications are met.