Acoustic performance of flexible bellows

Abstract

Bellows are generally used for vibration isolation in ducts. However, conical expansions and contractions lead to acoustic transmission loss as well. In this paper plane wave propagation through a bellow has been investigated. The wave equation for a stationary medium has been solved exactly with the help of a practical assumption. But, for the case of mean flow, with its convective as well as dissipative effects, an equivalent simple expansion-contraction chamber model has been developed based on some parametric studies. Effects of different parameters like thickness of the bellow wall, radius, length, and Mach number of mean flow have been studied. A reasonable agreement has been found between the theoretical and experimental results.