Abstract:

Previously, the idea of introducing a random height fluctuation to the conventional straight edge of a noise barrier was discussed as a way to increase insertion loss and improve acoustic performance. Here, an exhaustive set of experiments is discussed to more accurately discern the effects of the random edge. Experimental results were obtained using a spark source and a plywood barrier with interchangeable metal edges serving as the various edge profiles. Unlike the past experiments, which reported peak-to-peak sound pressures, results were obtained for the energy spectral density. The results indicate that the insertion loss data obtained with a random edge are not solely a function of Fresnel number as they are with a straight edge, and that local effects may dominate when considering the energy measured at a point in space. [This work was supported by a Texas Advanced Technology grant.]