Propagation of Sound through the Atmosphere: Effects of Ground Cover II
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)
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 30, 1979
- Accession Number
- ADA073262
Entities
People
- H. E. Bass
- L. N. Bolen
Organizations
- University of Mississippi