Cave Mapping

by Barry Fox NewScientist.com, 29 Nov 2005 Pursuing a suspect through an underground tunnel or cave is dangerous work for the police or military. But a system being developed at the University of Denver could make their lives a whole lot easier. Revealed in a recent patent finding, the system uses faint sound resonances to build a map of a hidden chamber and locate anyone hiding inside. Low frequency noise -- between 1 and 200 hertz -- is fed into the tunnel from a loudspeaker placed at its mouth. The cavity will then resonate at different strengths and frequencies depending on its shape. A microphone detects these resonances and a connected computer converts the audio information into a map showing the size and shape of the chamber on a screen. If anyone is hiding inside, their movement should alter the reflection pattern and thus changes the resonant spectrum. Tests show that the system works even when the person hiding is just 1/500th of the volume of the entire chamber. And the system should get more accurate with the creation of a database of resonant patterns relating to different cavity shapes. Read the cave mapping patent