IN-FLIGHT NOISE MEASUREMENTS PERFORMED ON THE X-21A LAMINAR FLOW AIRCRAFT

摘要

Sound pressure levels measured in flight by sis microphones positioned around the left hand wing of the X-21A laminar flow aircraft. These measurements define the noise levels existing at the wing surface for the Mach number ranges of the air-craft at three widely separated altitudes and four engine throttle settings,.nMost of the noise sources are identified, and it is shown that their levels compare favorably with previously developed prediction methods. It is noted,, however, that not all predominating noise sources are included in the prediction methods specifically engine screech, and one noise of undetermined origin It is also shown that engine noises are sacked at higher Mach numbers by radiated turbulent boundary layer noise, which has the properties of noise generated by a quadrupole mechanism.