Sound attenuation in lined bends

In the present paper we are concerned with sound propagation and attenuation in two- or three-dimensional lined bends. First it is shown that the effect of locally reacting absorbing materials at the walls of a waveguide can easily be taken into account in the multimodal formulation proposed in earlier papers by the authors, and, for bends, algebraic solutions are carried out for the acoustic field and scattering properties. Then a study of the sound attenuation in lined bends is given using the multimodal formulation and the properties of such waveguides are shown and discussed, in particular. the presence of a plateau of attenuation at high frequencies and a whispering gallery effect that occurs in bends. (C) 2004 Acoustical Society of America.