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Accession Number
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N20120010227
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Title
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Configuration Effects on Liner Performance.
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Publication Date
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Jun 2012
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Media Count
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17p
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Personal Author
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B. M. Howerton C. H. Gerhold M. C. Brown M. G. Jones
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Abstract
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The acoustic performance of a duct liner depends not only on the intrinsic properties of the liner but also on the configuration of the duct in which it is used. A series of experiments is performed in the NASA Langley Research Center Curved Duct Test Rig (at Mach 0.275) to evaluate the effect of duct configuration on the acoustic performance of single degree of freedom perforate-over-honeycomb liners. The liners form the sidewalls of the duct's test section. Variations of duct configuration include: asymmetric (liner on one side and hard wall opposite) and symmetric (liner on both sides) wall treatment; inlet and exhaust orientation, in which the sound propagates either against or with the flow; and straight and curved flow path. The effect that duct configuration has on the overall acoustic performance, particularly the shift in frequency and magnitude of peak attenuation, is quantified. The redistribution of incident mode content is shown. The liners constitute the side walls of the liner test section and the scatter of incident horizontal order 1 mode by the asymmetric treatment and order 2 mode by the symmetric treatment into order 0 mode is shown. Scatter of order 0 incident modes into higher order modes is also shown. This redistribution of mode content is significant because it indicates that the liner design can be manipulated such that energy is scattered into more highly attenuated modes, thus enhancing liner performance.
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Keywords
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Acoustic attenuation
Acoustic properties
Aerodynamic noise
Aircraft engines
Aircraft noise
Ducts
Engine noise
Honeycomb structures
Linings
Noise reduction
Walls
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Source Agency
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National Aeronautics and Space Administration
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NTIS Subject Category
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46A - Acoustics
68B - Noise Pollution & Control
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Corporate Author
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National Aeronautics and Space Administration, Hampton, VA. Langley Research Center.
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Document Type
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Conference proceedings
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Title Note
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N/A
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NTIS Issue Number
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1226
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Contract Number
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N/A
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