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Acoustic Transmission Through Cylindrical Shells Treated with FLD Mechanisms

Published online by Cambridge University Press:  05 May 2011

K. Daneshjou ,
R. Talebitooti  and
A. Nouri
K. Daneshjou*
Affiliation:
Department of Mechanical Engineering, Iran University of Science and Technology, Narmak, Tehran, Iran
R. Talebitooti*
Affiliation:
Department of Mechanical Engineering, Iran University of Science and Technology, Narmak, Tehran, Iran
A. Nouri*
Affiliation:
Department of Mechanical Engineering, Iran University of Science and Technology, Narmak, Tehran, Iran
*
* Professor
** Ph.D. student
** Ph.D. student
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Abstract

Analytical study is conducted in this paper to understand the characteristics of sound transmission through cylindrical shell with free layer damping (FLD) treatment. It is assumed an infinitely long circular cylindrical shell subjected to a plane wave with uniform airflow in the external fluid medium. The damping layer applied on the surface of the shell is represented by HN model with frequency-dependent specifications. An exact solution is obtained by solving the Markus equations of FLD shells and acoustic wave equations simultaneously. As the pressure and displacement terms are expressed in series form, an iterative procedure is founded to cut them with an appropriatenumber of modes. Transmission losses obtained from the solution are compared with “modal-impedance method” for an especial case of untreated shell. Eventually, the numerical results show the effects of stiffness, loss factor and thickness of damping material, and also incident wave angles on TL curves.

Keywords

WaveTransmission lossCylindrical shellFree layer damping

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Type
Articles
Information
Journal of Mechanics , Volume 25 , Issue 3 , September 2009 , pp. 299 - 306
Copyright
Copyright © The Society of Theoretical and Applied Mechanics, R.O.C. 2009

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