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Acoustic scattering by circular cylinders of various aspect ratiosThe effects of acoustic scattering on the useful frequency range of pressure gradient microphones were investigated experimentally between ka values of 0.407 and 4.232 using two circular cylindrical models (L/D = 0.5 and 0.25) having a 25 cm outside diameter. Small condenser microphones, attached to preamplifiers by flexible connectors, were installed from inside the cylindrical bodies, and flush mounted on the exterior surface of the cylinders. A 38 cm diameter woofer in a large speaker enclosure was used as the sound source. Surface pressure augmentation and phase differences were computed from measured data for various sound wave incidence angles. Results are graphically compared with theoretical predictions supplied by NASA for ka = 0.407, 2.288, and 4.232. All other results are tabulated in the appendices. With minor exceptions, the experimentally determined pressure augmentations agreed within 0.75 dB with theoretical predictions. The agreement for relative phase angles was within 5 percent without any exceptions. Scattering parameter variations with ka and L/D ratio, as computed from experimental data, are also presented.
Document ID
19790008471
Acquisition Source
Legacy CDMS
Document Type
Contractor Report (CR)
Authors
Maciulaitis, A.
(Grumman Aerospace Corp. Bethpage, NY, United States)
Date Acquired
September 3, 2013
Publication Date
January 1, 1979
Subject Category
Acoustics
Report/Patent Number
NASA-CR-3068
Accession Number
79N16642
Funding Number(s)
CONTRACT_GRANT: NAS1-14766
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.
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