Analysis and design of pod silencers

Munjal, ML (2003) Analysis and design of pod silencers. In: Journal of Sound and Vibration, 262 (3). pp. 497-507.

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Abstract

Parallel baffle mufflers or split silencers are used extensively in heating, ventilation and air conditioning systems for increased attenuation of noise within a short or given length. Acoustic analysis of rectangular parallel baffle mufflers runs on the same lines as that of a rectangular duct lined on two sides. This simplification would not hold for circular configurations. Often, a cylindrical pod is inserted into a circular lined duct to increase its attenuation (or transmission loss), thereby making the flow passage annular and providing an additional absorptive layer on the inner side of this annular passage. This configuration, called a pod silencer, is analyzed here for the four-pole parameters as well as transmission loss, making use of the bulk reaction model. The effect of thin protective film or a highly perforated metallic plate is duly incorporated by means of a grazing-flow impedance. Use of appropriate boundary conditions leads to a set of linear homogeneous equations which in turn lead to a transcendental frequency equation in the unknown complex axial wave number. This is solved by means of the Newton-Raphson method, and the axial wave number is then used in the expressions for transmission loss as well as the transfer matrix parameters. Finally, results of a parametric study are reported to help the designer in optimization of a pod silencer configuration within a given overall size for minimal cost.

Item Type:	Journal Article
Publication:	Journal of Sound and Vibration
Publisher:	Elsevier Science Ltd
Additional Information:	The copyright of this article belongs to Elsevier Science Ltd.
Keywords:	Automobile mufflers;Noise abatement;Boundary Conditions;Costs;Pod Silencers
Department/Centre:	Division of Mechanical Sciences > Mechanical Engineering
Date Deposited:	28 Jun 2004
Last Modified:	06 Jan 2012 06:34
URI:	http://eprints.iisc.ac.in/id/eprint/430

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