Abstract:

Previous experimental and field work has shown that rough surfaces may be modeled acoustically as though they were smooth surfaces with a modified surface impedance. In these works the roughness length scale used was a single parameter equal to 1/2 of the average height of the surface roughness elements. Recent experiments have suggested that this simple form for the roughness parameter may yield incorrect results for certain conditions such as grazing incidence over impermeable surfaces or sparsely scattered roughness elements. Modifications to this roughness parameter will be investigated. Specifically, the influence of the slope of the roughness elements, which is quantified using the standard deviation in height and the correlation length, will be investigated. [Work supported by the USDA ARS National Sedimentation Laboratory.]