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Report on directionality of sound radiation from clamped rectangular plate set in a baffle with attached masses: Theory and Experiment

Ramaiah, Pattabhi and Narayana, TSS and Sonti, Venkata R (2008) Report on directionality of sound radiation from clamped rectangular plate set in a baffle with attached masses: Theory and Experiment. [Preprint]

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Abstract

An analytical and experimental study is performed in which the directionality of sound radiated from a clamped plate set in a baffle is studied, by attaching masses to it. Analytically, the attachment of masses is done using the Receptance method [Soedel 1981], which generates the new mode shapes and the natural frequencies of the plate-mass system in terms of the old mode shapes and the natural frequencies. The Rayleigh Integral is then used to compute the sound field. The point mass locations are arbitrary but yet chosen where a unique directionality is exhibited. The analysis is done in the range of 500 Hz to 4000 Hz. In experiment, finite size masses are attached to the clamped plate set in a finite size baffle. The plate is then excited using a shaker and sound measurements are taken in the ’far field’ (where $L_I = L_p$) using a sound level meter. The match between theory and experiment is examined and explained. It is found that the excitation frequency to a large degree decides the sound field variations. However, the size of the masses and locations do influence the new mode shapes, and their relative contributions and hence the sound field. The problem is more complex when the number of masses is increased and or their weights are made different. It is demonstrated that the Receptance Method does give a reasonable accuracy in predicting natural frequencies of the new modes. Receptance being an analytical method, the entire calculation can be done free from FEM/BEM packages. It is also found that the area mass does not violate the point mass assumptions severely. The predicted directionality is very well achieved for the 2500 Hz three-mass case.

Item Type: Preprint
Additional Information: This report is an author's version and is not published.
Department/Centre: Division of Mechanical Sciences > Mechanical Engineering
Date Deposited: 20 Mar 2008
Last Modified: 19 Sep 2010 04:43
URI: http://eprints.iisc.ernet.in/id/eprint/13498

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