Application of coherence in fan noise studies
Joseph R. Balombin, United States. National Aeronautics and Space Administration. Scientific and Technical Information Office, Lewis Research Center
National Aeronautics and Space Administration, Scientific and Technical Information Office, 1980 - Crafts & Hobbies - 23 pages
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11 decibels 20 decibels 28 32 Frequency 90 percent speed 90-percent-speed anechoic chamber APPLICATION OF COHERENCE bandwidth Baseline o Inflow bias error blade passing frequency BPF level change in fan coherence 16 32 coherence analysis coherence function coherent BPF tone coherent data coherent power spectra coherent processing coherent sound pressure coherent spectrum component compute the coherent confidence limits configuration control and coherent data taken design speed digital signal processor FAN NOISE STUDIES fan rotor fan test fan was operated far-field microphone figure 17 filter bands fixed microphones herent hertz inflow control device inlet angle inlet quadrant kHz Figure Lewis Research Center lobe patterns measured coherence Microphone position NASA number of averages Number of samples obtain the coherence percent of design pressure lobes propagation quency random rotor-stator sound power levels sound pressure levels spatial survey microphone tion tone directivity tone frequency Total and coherent turbulence value of coherence variation