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Volume 5,     Number 2,     Spring 1997

 

SCATTERING OF A SPHERICAL SOUND WAVE
BY A RIGID SCREEN WITH
AN ABSORBENT EDGE IN A MOVING FLUID
S. ASGHAR AND TASAWAR HAYAT

Abstract. The scattering of a spherical wave (emanating due to a point source) by a semi-infinite plane in the presence of a moving fluid is investigated. A finite region in the vicinity of the edge has an absorbing boundary condition; the remaining part of the half plane is rigid. The problem which is solved is a mathematical model for a rigid barrier with an absorbent edge in the presence of a moving fluid. It is found that the absorbing material that comprises the edge need only be of the order of a wavelength long to have approximately the same effect on the sound attenuation in the shadow region of the barrier as a semi-infinite absorbent barrier. Also the softer the absorbent lining the greater the attenuation in the shadow region of the barrier. In the illuminated region a reduction in the sound intensity level can be achieved by a suitable choice of the absorptive material of the strip and its length. This investigation is important in the sense that point source is regarded as fundamental radiating device. It is found that a diffracted field is the sum of fields produced by the two edges. Finally, physical interpretation of the result is discussed.

 

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