Sound Detection of Caves

Extreme Endeavors partnered with NASA Langley in the development, testing and analysis of infrasonic sensor technology. Under the Innovative Partnerships Program, NASA funded the initial research between Extreme Endeavors and NASA Langley to produce a small, compact infrasonic sensor for the application of cave detection on Mars and listening for movement inside an underground facility.

There are some key advantages to using an infrasonic system. For starters, they have been known to provide low power-consumption solutions. Additionally (due to the excellent propagation characteristics of low frequency sound), these instruments could sense anomalies occurring at a considerable distance.

There is, however, one huge disadvantage that has restricted the use of infrasonic equipment in the past: its footprint size. Most applications require wind sound filtering, and this filter is approximately the size of a football field!  Not only does this take a considerable amount of real estate, but it also means that the construction and placement of the wind filter is a significant task that could take one or two days per system. This filter must also be operated on a large, flat region; thus, it is not feasible for a remote area, such as a mountain crag, inside a cave, or on the battlefield.  This large size limits the amount of sensors that can be placed, making triangulation difficult.

The technology under development at NASA Langley Research Center had drastically reduced the footprint of infrasonic sensors by using a foam sphere for wind filtration.  By using the infrasonic NASA technology, a “shoebox” size package can be designed that will sense with extreme accuracy the frequency range of .1 to 10 Hz.  (Specific modifications are required to make the device operate for the detection of caves.)   Utilizing three of these sensors we can pin-point