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Propagation and radiation of sound from flanged circular ducts with circumferentially varying wall admittances. I Semi-infinite ducts. II - Finite ducts with sourcesSound propagation in infinite, semiinfinite, and finite circular ducts with circumferentially varying wall admittances is investigated analytically. The infinite case is considered, and an example demonstrates the effects of wall-admittance distribution on dispersion characteristics and mode shapes. An exact solution is obtained for the semiinfinite case, a circular duct with a flanged opening: sidelobe suppression and circumferential-mode energy scattering leading to radiated-field asymmetry are found. A finite duct system with specified hard-walled pressure sources is examined in detail, evaluating reflection coefficients, transmission losses, and radiated-field directivity. Graphs and diagrams are provided, and the implications of the results obtained for the design of aircraft-turbofan inlet liners are discussed.
Document ID
19840051959
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Fuller, C. R.
(NASA Langley Research Center Hampton, VA, United States)
Date Acquired
August 12, 2013
Publication Date
April 8, 1984
Publication Information
Publication: Journal of Sound and Vibration
Volume: 93
ISSN: 0022-460X
Subject Category
Acoustics
Accession Number
84A34746
Distribution Limits
Public
Copyright
Other

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