Sound-wave propagation in a membrane-duct (L)

Theoretical analysis for sound waves in a flexible membrane mounted in an otherwise rigid duct is presented. It has been shown that supersonic fluid-dominant waves and subsonic membrane-dominant waves exist. The latter provides powerful mechanism of transmission loss through the membrane damping and destructive reflections at the edges of the membrane, while the cross-sectional area remains constant. The effect of mean flow and external fluid is also considered. (C) 2002 Acoustical Society of America.