Wei par Natl. Ctr. for Phys. Acoust., Univ. of Mississippi, University, MS 38677
David W. Hagstrum
U.S. Grain Marketing Res. Lab., Manhattan, KS 66502
In detecting insect infestations in bulk-stored grain using an array of acoustic sensors, it is important to know the range of sound transmission in grain. Preliminary tests [R. Hickling and W. Wei, Appl. Acoust. 44 (1995)] have shown that grain can be highly absorbing, depending on frequency, and this may limit the range at which insects can be detected. Tests were conducted with six different types of grain: hard and soft wheat, brown rice, soybeans, corn, and sorghum. The results were analyzed using sound-transmission theory in porous media. Transmission characteristics were determined and related to grain size and shape. Tests were conducted of the effect of grain depth. Data analysis provides a measure of the average spacing between grains. The relation of grain spacing to insect size is discussed.