The active control method was used to suppress the sound diffracted by an outdoor barrier. This method operated by the cancellation of the sound pressure at the diffraction edge of the barrier, which normally behaves like the virtual source of the diffracted field. The results of two experiments are shown in this paper. In the first experiment, we employed two independent controllers that utilized multi-channel adaptive signal processing to minimize the sum of the mean square of the sound pressure at four and six points along the diffraction edge. Measurement of sound pressure levels at various distances from the barrier showed effective sound suppression, with about 6-dB excess attenuation over the barrier's insertion loss at the receiver at a distance of 50 m. A practically realistic noise source, a fan blower, was used as a primary source in the second experiment and the moderate attenuation could be achieved at almost all the receiver points. The results obtained in these two experiments provided the experimental verification of the strategy for the active suppression of sound diffracted by a noise barrier.
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