Understanding of the Acoustic Characteristics of Bent Ducts

Abstract

Ducts are widely used in an industry field. For example, a high-power suction truck has a complex piping system which starts from a root blower to a final exit while repeating bend. The root blower generates a large pulsation and make resonance with the piping system. In order to avoid the resonance, it is necessary to know the natural acoustic frequency of the piping system．We already reported on the resonant frequency of sound fields in ducts with different diameters. This paper investigates the noise damping effects of bending in ducts with multiple bends. Additionally, the noise damping effects of inserting sound-absorbing materials into the duct were also examined. Through experiments and analysis, the frequencies at which damping effects occur were identified. Furthermore, it became clear that the frequencies at which damping effects occur vary depending on the inner diameter of the duct.