Shape discrimination of buried objects using an acoustic land mine detection system

An acoustics-based system has recently proved successful at detecting buried land mines. The present paper describes the use of this land mine detection system to discern shapes of buried objects. Steel plate targets of three shapes were used: circle, square, and equilateral triangle, each buried in sand with their major surface horizontal. In each case, for certain frequency bands, when a color-scaled spatial distribution of particle velocity amplitude is displayed in real time, the target shape is clearly visible. Calculations are made using a simplistic theoretical model in an effort to understand the frequency dependence of the experimental result. For each target, wave scattering is crudely mimicked by calculating the radiant pattern in an infinite fluid from a simple source distribution of the same shape as the target and visualizing its interference with plane incident wave. Limited qualitative understanding of experimental result is obtained with this crude mode, but the need for a more realistic scattering calculation is indicated.