Abstract:

An approximate analytical method for calculating the diffraction field behind a jagged-edge noise barrier, idealized as a thin rigid half-plane having an irregular edge, is presented. Experimental studies have shown that for apertures, disks, and plane barriers, making the edge irregular can significantly decrease the diffracted signal [Bailey et al., J. Acoust. Soc. Am. 92, 2359(A) (1992); Ho et al., J. Acoust. Soc. Am. 101, article in press (1997)]. Straight-edge diffraction from a rigid half-plane has a known exact solution for plane, cylindrical, and spherical incident waves. It is observed that in all three cases the shadow zone signal, in the far field, is equivalent to radiation from an infinite line source, but modified by a certain directivity function. In the present work the jagged edge is modeled as a crooked line source having the same directivity as a straight edge. The radiation is calculated by treating the crooked line as an infinite set of point sources, summing their contributions, and adding the appropriate directivity. The method is simple to apply. Results are compared with those found by other methods. [Work supported by Texas Advanced Technology Program.]