Propagation of Sound Through the Atmosphere: Effects of Ground Cover
Interim rept. Jun 76-Jun 78
MISSISSIPPI UNIV UNIVERSITY PHYSICAL ACOUSTICS RESEARCH LAB
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Measurements of sound amplitude in the vicinity of a ground plane have been made as a function of frequency of the sound source 100 Hz - 2000 Hz , distance of propagation 5m - 100m, and surface conditions. By treating the impedance as an adjustable parameter, the surface impedance as a function of frequency was determined from the measured amplitudes using the theoretical treatment of a spherical wave in the vicinity of a locally reacting surface. Measurements of the amount of energy coupled into the ground were also made using geophones below the ground surface. Experimental studies of surface impedance should include measurements of soil parameters such as density, specific flow resistance, and moisture content so that comparisons can be made between the results from different laboratories and so that a data base for additional theoretical development can be established.