To study the non-cavitating noise behavior of contra-rotating propellers,a method to predict the non-cavitating noise generated by a contra-rotating propeller was established on basis of acoustic theory. In this paper,a conventional contra-rotating propeller was used as the model sound source and the point of detected noise was studied. In addition,the paper employed the method of superposition of incoherent acoustic waves. The effects of some factors,which include the number of blades,propeller diameter,di...