A Subsurface Acoustic Imaging System

of soil were evaluated. The current study will describe the imaging system and present preliminary images produced from data collected from a soil phantom. W e have built the imaging system, which incorporates a single element source transducer and a receiver array, both obtained from the Applied Research Laboratory at Pennsylvania State University. The source and receiver array are moved together along a linear path to collect data to form a B-mode image. The source is well approximated as a point source. The transmitted signal is a eosine weighted pulse of 6 cycles at a center frequency of 6 kHz. A 52element sonar array (8x8, 3.56 cm2 close-packed elements with 3 elements missing from each corner) acts as the receiver and allows for beamforming on receive, which is accomplished off-line using delay-and-sum beamforming. This system is in operation at the U.S. Army Construction Engineering Research Laboratory (CERL) in Champaign, I t , where the data are collected in a controlled volume (120 x 120 x 60 cm) of dry sand. Using this system, we