Accession Number : AD0439351


Title :   IN-FLIGHT NOISE MEASUREMENTS PERFORMED ON THE X21A LAMINAR FLOW AIRCRAFT,


Corporate Author : NORTRONICS HAWTHORNE CALIF


Personal Author(s) : Carmichael,R F ; Pelke,D E


Report Date : Apr 1964


Pagination or Media Count : 69


Abstract : Sound pressure levels were measured in flight by six 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 aircraft at three widely separated altitudes and four engine throttle settings. Most 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 orgin. It is also shown that engine noises are masked at higher Mach numbers by radiated turbulent boundary layer noise, which has the properties of noise generated by a quadrupole mechanism. In regards to the effects of noise on the maintenance of laminar flow, it is noted that noise spectra possessing intense, relatively narrow band spikes could be more detrimental than flat spectra with higher over-all levels. (Author)


Descriptors :   *BOUNDARY LAYER TRANSITION , AIRCRAFT NOISE , LAMINAR FLOW , JET AIRCRAFT , MEASUREMENT , INSTRUMENTATION , MICROPHONES , TURBULENT BOUNDARY LAYER , TURBOJET ENGINES , JET ENGINE NOISE , TURBOJET INLETS , RESEARCH AIRCRAFT , COMPRESSOR NOISE , NOISE


Distribution Statement : APPROVED FOR PUBLIC RELEASE