Abstract
The directivity of the diffracted field around a half-plane barrier is investigated. Experiments were carried out in air using a spark source generating N-shaped pulses, a capacitor microphone, and a rigid aluminum plate with: (i) straight top edge (reference case), (ii) jagged top edge, and (iii) straight edge covered with sound absorptive material. Measurements were taken around the plate by varying the angular position of the microphone while keeping its radial distance from the barrier edge constant. The following were observed: (i) Straight edge: The diffracted pulse changes polarity as it passes across the two shadow boundaries and the continuation of the barrier in the half-space above it. (ii) Jagged edge: Although jaggedness in the top edge of the barrier drastically changes the shape of the diffracted pulse, the directivity pattern remains roughly the same. (iii) Sound absorptive edge: Although the shape of the diffracted pulse remains the same as in the reference case, the directivity patterns change considerably and changes are more pronounced at the source side. The experimental data and observations were in good agreement with theoretical predictions from the Directive Line Source Model [Menounou et al., J. Acoust. Soc. Am. 107, 103–111 (2000)]. [Work supported by Texas ATP.]