The Behm Acoustic Sounder for Airplanes with Reference to Its Accuracy
This is a 1930 NACA technical memorandum on the Behm acoustic sounder, an airborne echo-ranging instrument for measuring altitude, issued by the National Advisory Committee for Aeronautics for aviation engineers and instrument designers. The pictures are plain graph charts of calculated error curves plotted against distance and velocity, with labelled families of lettered lines on gridded axes, offering a designer little beyond the chart format and its line-and-grid conventions.
