Noise from Two-Blade Propellers
A 1936 technical report from the National Advisory Committee for Aeronautics (NACA), issued through the NASA Technical Reports Server, presenting measurements of noise produced by two-blade aircraft propellers for engineers and acousticians. The pictures are plain engineering graphs and charts: oscillogram strips of sound traces, a family of loudness curves across frequencies in decibels, humidity response curves, and polar diagrams of loudness around a propeller, all in black ink on white. A designer might borrow their dense grid layouts, labelled axes and scientific chart typography.
