Figs.22.23,24 N.A.C.A. Technical Memorandiun No, 825 ''ZSO 270 Z90 V 370m/s330 Figure 24.- Ratio of acoustical Figure 22.- Directional ef- power to power loss of fect of rotation propeller versus tip speed. noise. … Figure 23.- Sound intensity of rotation note and of rotation noise versus tip speed.
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