Acoustic Diffraction by an Impedance-Covered Edge.
PENNSYLVANIA STATE UNIV UNIVERSITY PARK APPLIED RESEARCH LAB
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The prediction of the sound scattered by impedance covered wedges is obtained by use of dual integral equations. The impedance of each face of the wedge is modeled as a point reacting complex quantity which is independent of the other face. The solution was constructed as an angular spectrum to satisfy the boundary conditions and Sommerfeld radiation condition. The solution kernel was obtained exactly and is in terms of circular functions. The solution of the scattered pressure was then obtained for far-field and mid-range by use of asymptotic techniques. This solution is much simpler than the one developed by Russian scientists for example, see G.D. Maliuzhinets, The Radiation of Sound by Vibrating Boundaries of an Arbitrary Wedge, Parts 1 and 2, Soviet Physics Acoustics, pp. 152-174 and 240-248 1955 which was obtained by a method similar to Wiener-Hopf technique. Thus, it is easier to use in highway noise applications because of its simplicity. The solution for the diffracted pressure exhibits clearly the role of the incident and reflected shadow boundaries and shows there is one minimum in the scattered field which depends on the two surface impedances. For backscattered pressure, the solution exhibits two minima. In all cases, the scattered pressure becomes negligible near the wedge surfaces. Author
- Numerical Mathematics