Machine Design

Sound Beams Spot Land Mines

An estimated 26,000 people are killed or injured every year by land mines and while the casualties include soldiers, most are civilians, half of them children under 16 years old, who step on uncleared minefields after a war.

Julie Kalista
Online Editor

MIT Lincoln Laboratory researchers are developing a sonic beam that seeks out buried mines the way bats seek out their prey.
Photo Credit: Jon Barron, MIT Lincoln Lab
And there are still 60 to 70 million undetected land mines out there. "Reliable methods that quickly and accurately locate land mines made of metal and plastic are desperately needed," according to Massachusetts Institute of Technology (MIT) researcher Robert Haupt.

Haupt and his team developed parametric acoustic arrays (with more power than a jet engine) made up of ceramic transducers that emit ultrasonic waves that measure 155 dB after they travel one meter away. When the sound beam hits buried mines, they vibrate and resonate from the sound waves and push up on the ground. These vibrations are then measured with a laser-based Doppler vibrometer. "Mines have a sound signature unlike anything else that let you determine the types of mines and even the countries that made them by their acoustic signatures," says Haupt. Because the acoustic intensity dies away to almost nothing outside the beam, like a flashlight of sound, it will not harm operators or those nearby.

The prototype detector was tested at the Cold Regions Research and Engineering Laboratory Army Corps of Engineers landmine facility in New Hampshire, CT. The researchers were able to detect both metal and plastic mines but said the system will need a major boost in acoustic power before minefield searchers can use it safely. The researchers also hope to tailor the system to detect damage in cement bridge piers from as far away as the shore.

More Information:
Massachusetts Institute of Technology (MIT)

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