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Advances in Acoustics and Vibration
Volume 2014 (2014), Article ID 392138, 11 pages
http://dx.doi.org/10.1155/2014/392138
Research Article

Sound Scattering and Its Reduction by a Janus Sphere Type

1School of Engineering and Materials Science, Queen Mary University of London, London E1 4NS, UK
2School of Engineering, Tel Aviv University, Tel Aviv, Israel

Received 28 May 2014; Revised 11 August 2014; Accepted 30 August 2014; Published 18 September 2014

Academic Editor: Abdelkrim Khelif

Copyright © 2014 Deliya Kim et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Sound scattering by a Janus sphere type is considered. The sphere has two surface zones: a soft surface of zero acoustic impedance and a hard surface of infinite acoustic impedance. The zones are arranged such that axisymmetry of the sound field is preserved. The equivalent source method is used to compute the sound field. It is shown that, by varying the sizes of the soft and hard zones on the sphere, a significant reduction can be achieved in the scattered acoustic power and upstream directivity when the sphere is near a free surface and its soft zone faces the incoming wave and vice versa for a hard ground. In both cases the size of the sphere’s hard zone is much larger than that of its soft zone. The boundary location between the two zones coincides with the location of a zero pressure line of the incoming standing sound wave, thus masking the sphere within the sound field reflected by the free surface or the hard ground. The reduction in the scattered acoustic power diminishes when the sphere is placed in free space. Variations of the scattered acoustic power and directivity with the sound frequency are also given and discussed.