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기술보고서

기술보고서 게시판 내용
타이틀	Locating and Quantifying Broadband Fan Sources Using In-Duct Microphones
저자	Dougherty, Robert P.;; Walker, Bruce E.;; Sutliff, Daniel L.
Keyword	AEROACOUSTICS;; AERODYNAMIC NOISE;; AIRCRAFT NOISE;; ANNULAR DUCTS;; BEAMFORMING;; BROADBAND;; FAN BLADES;; MICROPHONES;; NOISE MEASUREMENT;; NOISE REDUCTION
URL	http://hdl.handle.net/2060/20110003094
보고서번호	NASA/TM-2010-216931
발행년도	2010
출처	NTRS (NASA Technical Report Server)
ABSTRACT	In-duct beamforming techniques have been developed for locating broadband noise sources on a low-speed fan and quantifying the acoustic power in the inlet and aft fan ducts. The NASA Glenn Research Center''s Advanced Noise Control Fan was used as a test bed. Several of the blades were modified to provide a broadband source to evaluate the efficacy of the in-duct beamforming technique. Phased arrays consisting of rings and line arrays of microphones were employed. For the imaging, the data were mathematically resampled in the frame of reference of the rotating fan. For both the imaging and power measurement steps, array steering vectors were computed using annular duct modal expansions, selected subsets of the cross spectral matrix elements were used, and the DAMAS and CLEAN-SC deconvolution algorithms were applied.