Accession Number:

ADA073262

Title:

Propagation of Sound through the Atmosphere: Effects of Ground Cover II

Descriptive Note:

Final rept. 1976-1979

Corporate Author:

MISSISSIPPI UNIV UNIVERSITY PHYSICAL ACOUSTICS RESEARCH LAB

Personal Author(s):

Report Date:

1979-06-30

Pagination or Media Count:

55.0

Abstract:

Measurements of sound amplitude in the vicinity of a ground plane have been made as a function of frequency of the sound source 50 Hz - 2000 Hz, distance of propagation 5m - 300m, and surface conditions. By treating the impedance as an adjustable parameter, the surface impedance as a fucntion of frequency was determined from the measured amplitudes using a theoretical treatment of a spherical wave in the vicinity of a locally reacting surface. The impedance measurements covered the frequency range 50 Hz to 1000 Hz. In this frequency range, the results for three distinctly different surfaces suggest that the impedance can be computed from the specific flow resistance and that grass has little effect on the surface impedance except for decreasing the flow resistance due to the root structure. Experimental studies of surface impedance should include measurements of soil parameteres 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. Author

Subject Categories:

  • Acoustics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE