Acoustic sensor could help combat human trafficking

MIT Technology Review : Detecting people being illegally transported across borders has proven difficult when they are hidden in metal enclosures, such as cargo containers, trailer trucks, or train cars. The metal walls block microwaves, the darkness renders millimeter-wave sensors useless, and gamma rays pose a health hazard for humans. Now Franklin Felber of Starmark Inc has demonstrated the effectiveness of a high-power acoustic sensor , which uses a hammer banging on a metal disk to create acoustic signals at discrete frequencies that can easily pass through any metal barrier to which the device is attached. By comparing the signals as they are reflected off objects on the other side of the wall, the sensor can distinguish moving objects from stationary ones and is sensitive enough to detect the presence of a person merely by his or her breathing. The company next needs to test whether the device can be scaled up to scan thousands of cargo containers in all weather conditions.