Bulk Reaction Modeling of Sound Propagation Through Circular Dissipative Ducts Backed by an Air Gap

Abstract

Circular and annular dissipative ducts are extensively used for attenuation of sound in industrial applications. In most of the cases the characteristics of lining material is considered to be locally reacting, although; it may not be true always. This is because there are not many investigations available for bulk reaction modeling of circular and annular ducts. The present paper deals with a generalized formulation of a sound wave with mean and induced flow for bulk reaction approach, which can analyze sound attenuation and phase speed in circular and annular cross-section ducts. In the absence of extensive experimental data, the present theoretical model is validated by comparing a few sets of results with some published experimental results. The theoretical results are presented for various parameters of duct and lining material. More emphasis has been given to the effect of the air gap between the lining and rigid wall on the rate of attenuation and phase speed. It has been demonstrated through various sets of results that the air gap between the lining and rigid wall has a great effect on the overall performance of dissipative ducts. The present model can be used to analyze the sound field in air conditioning ducts and other similar applications.