Influence of design parameters on sound power spectrum for general aviation propellers in forward flight

Theory and results are presented for the sound power and sound power spectrum of a single rotation propeller in forward flight. Calculations are based on the linear wave equation with sources distributed over helicoidal surfaces to represent effects of blade thickness and steady loading. Sound power is distributed continuously over frequency, as would be expected front Doppler effects, rather than in discrete harmonics. The theory is applied to study effects of number of blades to the total sound power produced for cruise mode and their sound power spectrum.