Donskoy's system works by using a loud speaker to simultaneously blast two deep frequencies over the minefield. The sound waves cause the mine to vibrate, and these vibrations disturb the surface soil directly above the mine. A laser sensor detects the minute surface vibrations, which are recorded by a computer and used to pinpoint the location of the mine.
The "nonlinear seismo-acoustic" land mine detection system, as Donskoy calls it, can distinguish mines from other buried debris because of a "bouncing effect" that occurs at the interface of the flexible mine container and the soil. The activity distorts the two original frequencies and produces a new frequency that causes the vibrations at the surface of soil.
"Rocks and other solids do not distort the two frequencies because they do not vibrate as easily when hit with sound waves," Donskoy explained.
A test of more than 50 types of minesplastic, wooden, and metalrevealed that each had a different vibration when excited with the two frequencies, and then responded by producing its own distinctive "acoustic signature."
"This is our best near-term bet," said the NVESD physicist, noting that if further field tests are successful, the technology could be ready for use in the next couple of years. The next phase of field tests is scheduled for mid-April.
Scientists led by James Sabatier at the University of Mississippi have developed a similar acoustic technology that uses one frequency at a time rather than two, said the NVESD scientist. While Sabatier's technology is faster and better at detecting larger anti-tank land mines, it had a much higher rate of false hits when detecting smaller anti-personnel mines, he added.
Mine detection is a very difficult task and a successful system will probably integrate several types of sensors, said the NVESD scientist. "Both the Stevens and Mississippi technology are still under investigation, but if they are successful they will probably be combined into a single system," he said. Army funding for these two projects over the last five years and the current year has been almost $9 million.
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