Abstract:
The propagation of sound over finite impedance rough surfaces is investigated. Laboratory experiments have illustrated that roughness can be treated as an effective impedance in propagation models. This finding holds for high- and low-impedance surfaces and is valid for propagation at grazing and nongrazing incidence. The purpose of this present work is to find out if these trends persist in the propagation of sound over rough soil surfaces outdoors. Of specific interest is the inverse problem of determining the roughness scale from the acoustic propagation. Previous field measurements were unable to separate the attenuation due to roughness and that due to the changes in the ground impedance caused by creating the roughness. Future experiments will examine surfaces that have been sufficiently weathered so that the parameters that influence impedance, such as porosity and flow resistivity, are comparable between rough surfaces and nearby smooth surfaces. [Work supported by USDA.]