Inside Out Library · ExploreNoise from Propellers with Symmetrical Sections at Zero Blade Angle (1937)NASA Technical Reports Server (NTRS) · leaf 25Figure 4.- Sound-measuring equipmentNASA Technical Reports Server (NTRS)Internet Archive · NASA Technical Reports · Public domain (US government work). Free to use for anything.More pictures from Noise from Propellers with Symmetrical Sections at Zero Blade AngleMore like this
