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Three-dimensional acoustic analysis of an elliptical chamber muffler with a side inlet and a side outlet

Mimani, A and Munjal, ML (2011) Three-dimensional acoustic analysis of an elliptical chamber muffler with a side inlet and a side outlet. In: 18th International Congress on Sound and Vibration, 10-14 July 2011, Rio de Janeiro.

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The acoustical behaviour of an elliptical chamber muffler having a side inlet and side outlet port is analyzed in this paper, wherein a uniform velocity piston source is assumed to model the 3-D acoustic field in the elliptical chamber cavity. Towards this end, we consider the modal expansion of the acoustic pressure field in the elliptical cavity in terms of the angular and radial Mathieu func-tions, subjected to the rigid wall condition. Then, the Green's function due to the point source lo-cated on the side (curved) surface of the elliptical chamber is obtained. On integrating this function over the elliptical piston area on the curved surface of the elliptical chamber and subsequent divi-sion by the area of the elliptic piston, one obtains the acoustic pressure field due to the piston driven source which is equivalent to considering plane wave propagation in the side ports. Thus, one can obtain the acoustic pressure response functions, i.e., the impedance matrix (Z) parameters due to the sources (ports) located on the side surface, from which one may also obtain a progressive wave rep-resentation in terms of the scattering matrix (S). Finally, the acoustic performance of the muffler is evaluated in terms of the Transmission loss (TL) which is computed in terms of the scattering pa-rameters. The effect of the axial length of the muffler and the angular location of the ports on the TL characteristics is studied in detail. The acoustically long chambers show dominant axial plane wave propagation while the TL spectrum of short chambers indicates the dominance of the trans-versal modes. The 3-D analytical results are compared with the 3-D FEM simulations carried on a commercial software and are shown to be in an excellent agreement, thereby validating the analyti-cal procedure suggested in this work.

Item Type: Conference Proceedings
Publisher: Curran Associates, Inc
Additional Information: Copyright of this article belongs to Curran Associates, Inc.
Department/Centre: Division of Mechanical Sciences > Mechanical Engineering
Date Deposited: 06 May 2013 12:13
Last Modified: 06 May 2013 12:13
URI: http://eprints.iisc.ac.in/id/eprint/46296

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