A NOTE ON SHORT-RANGE GROUND CHARACTERIZATION

Short-range measurements of the excess attenuation spectrum from a poi nt source can be used to characterize the acoustical properties of the ground surface but they are influenced by turbulence as well as the g round surface. The geometry used for ground characterization should be a compromise between greatest sensitivity to the acoustical propertie s of the ground surface and avoidance of turbulence effects. Compromis e geometries are suggested together with a method of estimating the ef fective flow resistivity of the ground surface from the frequency of t he first maximum in the excess attenuation spectrum. The use of this m ethod is illustrated for a particular grass-covered farmland.