A comparison between the SR-6 propeller noise in flight and in a wind tunnel

High-speed turboprops offer an attractive candidate for future aircraft because of their high propulsive efficiency. However, one of the possible problems associated with these propellers is a high level at cruise that might create a cabin environment problem for future aircraft powered by these propellers. Models of these propellers have been tested for acoustics in the Lewis 8-by-6-ft wind tunnel and on the Dryden JetStar airplane. This paper shows comparisons between the airplane and wind tunnel data for the SR-6 propeller. The comparison of the maximum blade passing tone variation with helical tip Mach number taken in flight with that taken in the tunnel showed good agreement when corrected to the same test conditions. Directivity comparisons also showed fairly good agreement. These good comparisons indicate that the wind tunnel is a viable location for measuring the blade passage tone of these propellers.