Measurements and predictions of turboprop noise at high cruise speed

Acoustic tests of advanced turboprop (Prop-Fan) models have taken place in or on three facilities: an acoustic wind tunnel, an aerodynamic wind tunnel, and a flight vehicle. Comparisons of data from the three facilities are made for two model designs, the unswept SR-2 and the swept SR-3. The importance of noise propagation through the boundary layer to microphones mounted on the surface of a flight vehicle is discussed and limited comparisons between predictions and measurements are shown. It is concluded that existing methodology is adequate for predictions at high cruise Mach number and that further development is required to improve the methodology for predicting fuselage and wind tunnel boundary layer propagation effects.