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Rienstra, S.W. (author)The present report describes a theory to calculate the sound propagation (including attenuation, reflection, radiation) through a three-sectioned cylindrical flow duct, modelling an aero-engine inlet. The flow is uniform apart from a thin boundary layer; two of the three sections are hardwalled, with an impedance-walled section in between. The...report 1987
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Laan, J.N. (author)It is concluded from this limited analytic study of pure tone sound suppression in a cylindrical duct with uniform flow, based on the mode matching technique, that the optimum of the liner impedance heavily depends on the source distribution and also on the length of the duct.report 1981
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Laan, J.N. (author)A set of equations is presented for the sound propagation in an axisymmetric multisectional duct. For each side of a source section the combined duct effects of transmission, reflection and absorption are reduced to one matrix of coefficients. The procedure is compatible with a source description which takes the feedback of the sound field into...report 1979
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Laan, J.N. (author)In this report the sound propagation in a hard-walled annular duct of finite length is investigated. The individual modal solutions so found are described. The main properties which are calculated in the present report, are the modal intensity and the modal far field directivity pattern. The modal intensity is determined by the rate of mode...report 1975
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Tiggelaar, J.J. (author)The sound field in an infinitely long duct with shear flow and sound absorbing walls, but with the sound source unspecified, is analysed into its constituents, the acoustic duct modes. The equations, wave numbers, and various properties of the modes are discussed. Some calculated results are used to show the effects of shear flow and absorbing...report 1975