James P. Chambers
James M. Sabatier
Natl. Ctr. for Physical Acoust., Univ. of Mississippi, University, MS 38677
The propagation of sound over rough surfaces of finite impedance is investigated. Initial experiments have illustrated the excess attenuation caused by roughness, that is, attenuation above and beyond that caused by geometrical spreading alone. These initial experiments were conducted indoors in a well-controlled setting for sound at grazing incidence. These measurements also show good agreement with Attenborough's proposed model [J. Acoust. Soc. Am. 95(5), 2838(A) (1994)] that incorporates the effects of roughness into an effective admittance. The purpose of this present work is to find out if these trends persist in the propagation of sound over rough surfaces in a real-world setting. Sound signals will be measured above both rough and smooth agricultural surfaces with varying roughness profiles. Additional measurements will be made to determine the impedance and wave number of the surface as well as the roughness profile in order to examine Attenborough's model in more detail. [Work supported by USDA.]