## Experimental validation of a two-dimensional shear-flow model for determining acoustic impedanceNational Aeronautics and Space Administration, Scientific and Technical Information Branch, 1987 - Science - 46 pages |

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3.0 Frequency 30 Axial distance Acoustic Impedance acoustic pressure profile admittance aeroacoustic antiresonance attenuation and phase axial acoustic pressure axial attenuation axial propagation constant centerline Mach number ceramic honeycomb coef Data Least-square fit dB Slope dB/cm Corr deg Slope deg/cm downstream and upstream downstream propagation Duct Liners equation flow duct flow Mach number grazing flow impedance data impedance measurements incidence impedance infinite-wave-guide method Langley Research Center level attenuation profile linear least-square fit manometer math model Mc/L Measured axial acoustic measured propagation constant NASA normal-incidence impedance null location number of 0.3 order mode phase profiles pressure level attenuation profile at Mach profile slopes propagation model propagation with error random measurement reactance reference location shear Sound pressure level standing wave ratios static pressure systematic errors tenuation test frequencies test section test specimen test specimen leading tion total and static two-dimensional shear-flow model velocity profile