A NOTE ON SHORT-RANGE GROUND CHARACTERIZATION

Short-range measurements of the excess attenuation spectrum from a point source can be used to characterize the acoustical properties of the ground surface but they are influenced by turbulence as well as the ground surface. The geometry used for ground characterization should be a compromise between greatest sensitivity to the acoustical properties of the ground surface and avoidance of turbulence effects. Compromise geometries are suggested together with a method of estimating the effective flow resistivity of the ground surface from the frequency of the first maximum in the excess attenuation spectrum. The use of this method is illustrated for a particular grass-covered farmland.