The acoustic array developed by Robert Haupt, a researcher at the Massachusetts Institute of Technology, looks like a dart board and emits highly concentrated beam of sound waves at high ultrasonic frequencies aimed at the minefield.
Through a process known as self-demodulation, the air in front of the beam converts the ultrasound to lower frequency audible sound as it travels over a distance of about 10 metres.
Unlike ultrasound, audible sound can travel through the ground. When the highly concentrated sound waves hit a solid object, they cause it to vibrate.
The vibrations make their way to the surface where they are detected by a laser system that measures vibrations in the ground, reported the online edition of New Scientist.
Tests in the US suggest that the prototype could reveal hidden mines more accurately than the devices currently in use. The cost of the new system would be considerably more than hand held metal detectors.
While the new system can scan flat open fields quickly and efficiently, sloping terrain or thick vegetation could obscure the view of the ground that the laser system requires to detect vibrations.
...hand held metal detectors...have a limited range and so can miss mines that are deeply buried. Plastic mines...go unnoticed.
...metal detectors...can only be used by minesweepers inside a minefield.