Detecting land mines with sound
January 23, 2007Researchers at MIT's Lincoln Laboratory are developing a highly pinpointed sound beam that can detect buried land mines from a safe distance. The new beam will use sound to seek out land mines like a bat uses sonar to hunt its prey.
The researchers built a prototype detector and tested it at the Cold Regions Research and Engineering Laboratory Army Corps of Engineers land-mine facility in New Hampshire. They were able to detect both metal and plastic mines but said that the system will have to get a major boost in acoustic power before minefield searchers can use it safely.
Robert W. Haupt, a technical staff member at Lincoln Lab, explores innovative ways to find and reduce the large number of land mines abandoned in war-torn countries. An estimated 26,000 people are killed or maimed every year by 60 to 70 million undetected land mines in 70 countries. Those casualties include military troops but most are civilians--half of them children under age 16--who step on uncleared minefields after a war.
Many existing prototype mine detection systems can detect only metal, have limited range or are impractical in the field. "Reliable methods that quickly and accurately locate land mines made of metal and plastic, unexploded ordnance and other mine-like targets are desperately needed," Haupt said.
Haupt and fellow Lincoln Lab staff member Ken Rolt developed a high-powered sound transmitter that looks like a stop sign studded with 35mm film canisters or prescription pill containers. This is called a parametric acoustic array, and Haupt and Rolt have built one of the most powerful ones around.
The array is made up of ceramic transducers--devices that emit a powerful narrow acoustic beam at ultrasonic frequencies. One meter away, the ultrasonic pressure level measures 155 decibels--more acoustic power than a jet engine. Immediately outside the beam, the acoustic intensity dies away to almost nothing.
By a process know as self-demodulation, the air in front of the acoustic beam converts the ultrasound to much lower frequency audible tones that sound like extremely loud tuning forks. Unlike ultrasound, the low-frequency sound can penetrate the ground, causing detectable vibrations in the mine's plungers and membranes.
"The use of ultrasound allows us to make a very narrow and highly directional beam, like a sound flashlight," Haupt said. It would take a huge number of conventional loudspeakers to do the same trick, and they would weigh too much, take up too much space and use too much power to be practical, he said. Plus, they would deafen anyone within earshot. "Using a narrow sound beam, we can put sound just where we want it, and we can minimize sound levels outside the beam to avoid harming the operators or people nearby," he said.
Once the sound beam "hits" buried ordnance, the vibrations from the mine, resonating from the sound waves, push up on the ground and can be measured remotely with a laser system called a Doppler vibrometer. The sound signature of a mine looks like a mountain range of spikes compared with the flat-line response of the rocks and dirt around it.
"It turns out that mines will vibrate quite differently from anything else," Haupt said. "You can determine what types of mines there are--and which countries made them--by their unique signatures."
Haupt also is working with Oral Buyukozturk, professor of civil engineering at MIT, to tailor the system to detect damage in cement bridge piers from as far away as the shore.
A paper on the land-mines work by Haupt and Rolt appeared in a 2005 issue of the MIT Lincoln Laboratory Journal. A second paper by Haupt was published in 2004 by the International Society for Optical Engineering.
Source: MIT
-
Student innovator uses sound waves, T-rays for safer detection of bombs
Mar 09, 2011 |
5 / 5 (2) |
0
-
The Eerie Silence
Apr 15, 2010 |
4.8 / 5 (36) |
71
-
Microwaving Water from Moondust (w/ Video)
Oct 08, 2009 |
4.8 / 5 (6) |
2
-
Look Ma! No (Human) Hands!
Mar 05, 2007 |
4.3 / 5 (3) |
0
-
Engineers build first sub-10-nm carbon nanotube transistor
Feb 01, 2012 |
4.9 / 5 (31) |
30
-
Something old, something new: Evolution and the structural divergence of duplicate genes
Jan 31, 2012 |
4.6 / 5 (7) |
1
-
The hidden nanoworld of ice crystals: Revealing the dynamic behavior of quasi-liquid layers
Jan 30, 2012 |
5 / 5 (3) |
1
-
Stock market network reveals investor clustering
Jan 27, 2012 |
3.9 / 5 (23) |
8
-
Of microchemistry and molecules: Electronic microfluidic device synthesizes biocompatible probes
Jan 26, 2012 |
5 / 5 (1) |
0
-
Need help reading 3-D
3 hours ago
-
A way to send and receive wireless data
9 hours ago
-
Tabletop Cold Fusion Reactor
11 hours ago
-
Calling function with no input argument
Feb 10, 2012
-
Force free body diagram problem on gym equipment
Feb 10, 2012
-
Empirical data regarding shower heads and water
Feb 10, 2012
- More from Physics Forums - General Engineering
More news stories
Walney offshore wind farm is world's biggest (for now)
(PhysOrg.com) -- The Walney wind farm on the Irish Sea--characterized by high tides, waves and windy weather--officially opened this week. The farm is treated in the press as a very big deal as the Walney ...
GPS court ruling leaves US phone tracking unclear
A US Supreme Court decision requiring a warrant to place a GPS device on the car of a criminal suspect leaves unresolved the bigger issue of police tracking using mobile phones, legal experts say.
13 hours ago |
4 / 5 (2) |
0
Europeans protest controversial Internet pact
Tens of thousands of people marched in protests in more than a dozen European cities Saturday against a controversial anti-online piracy pact that critics say could curtail Internet freedom.
9 hours ago |
5 / 5 (5) |
0
Netflix settlement trims 14 pct off 4Q earnings
(AP) -- Netflix pressed the rewind button on its fourth-quarter earnings after settling allegations that the video subscription service violated a consumer-privacy law.
13 hours ago |
not rated yet |
0
Navy to begin tests on electromagnetic railgun prototype launcher
The Office of Naval Research (ONR)'s Electromagnetic (EM) Railgun program will take an important step forward in the coming weeks when the first industry railgun prototype launcher is tested at a facility ...
Feb 06, 2012 |
4.7 / 5 (15) |
90
|
Europe stakes billion-dollar bet on new rocket
A pencil-slim rocket is scheduled to lift into space from South America on Monday, carrying a billion-dollar bet that Europe can grab a juicy slice of the market to place satellites in low orbit.
Study finds that anti-diabetic medication can prevent the long-term effects of maternal obesity
In a study to be presented today at the Society for Maternal-Fetal Medicine's annual meeting, The Pregnancy Meeting, in Dallas, Texas, researchers will report findings that show that short therapy with the anti-diabetic medication ...
Steroid injections prove effective in treatment of lumbar disc herniations
The use of epidural steroid injections may be a more efficient treatment option for lumbar disc herniations, according to research presented today at the American Orthopaedic Society for Sports Medicine's Specialty Day in ...
Amateur football players not always keen on returning to play after ACL injuries
Despite the known success rates of reconstructive Anterior Cruciate Ligament (ACL) surgery, the number of high school and collegiate football players returning to play may not be as high as anticipated, say researchers presenting ...
Study finds elevated levels of cell-free DNA in first trimester do not predict preeclampsia
In a study to be presented today at the Society for Maternal-Fetal Medicine's annual meeting, The Pregnancy Meeting, in Dallas, Texas, researchers will report findings that indicate that elevated levels of cell-free DNA in ...
PRP treatment aids healing of elbow injuries say researchers
As elbow injuries continue to rise, especially in pitchers, procedures to help treat and get players back in the game quickly have been difficult to come by. However, a newer treatment called platelet rich plasma (PRP) may ...