Further comparisons of wind tunnel and airplane acoustic data for advanced design high-speed propeller models

The noise of high‐tip‐speed propellers at cruise has been identified as a possible cabin noise problem for advanced turboprop airplanes. Comparisons were made between the SR‐2 and SR‐3 model propeller noise data taken in the NASA 8×6 wind tunnel, in the United Technologies Research Center (UTRC) Anechoic Tunnel, and with boom and fuselage microphones on the NASA Jetstar airplane. Plots of peak blade passage tone noise versus helical tip Mach number generally showed good agreement. The curve shapes were similar except for the UTRC data, which was flatter than the other sets. This was attributed to the UTRC data being taken at constant power while the other data were at constant advance ratio. Directivity shape comparisons at the cruise condition were also similar. The generally good comparisons of the data from four configurations using three facilities indicates the ability to use any of these facilities for measuring the blade passage tone noise of these types of propellers.