A sound's loudness has the greatest impact on maximum accurate detection range, although ground cover, weather and other factors do affect sensor capabilities to a small extent, de Bree says. The sensors can pinpoint:
- A 155-millimeter howitzer—at 175 decibels—from up to 40 kilometers away
- An 81-millimeter mortar—at 180 decibels—from 25 kilometers away
- 5.56-millimeter small arms fire—at 155 decibels—from five kilometers away
- A normal, 60-decibel conversation from up to 50 meters away
Those figures hold regardless of whether a sensor is airborne or on the ground, de Bree says. And although effective individually, networking multiple systems mounted on drones, tanks and soldiers would extend their range to create more-robust battlefield views.
Military representatives from the U.S. and U.K. as well as Russia and Israel stood on a Royal Netherlands Army (RNA) mortar range in 2012 watching a demonstration of the sensor's abilities, Jacobs says. The Microflown sensors that day were integrated with a new Royal Netherlands Navy radar. Jacobs says they were astonished by the system's accuracy.
The mortar-range sensor project, which cost about $1.3 million over two years, spurred an RNA "development roadmap" that includes sensor-equipped drones, helicopters and ground vehicles, Jacobs says. De Bree confirmed that the RNA has ongoing trials putting sensors on air and ground assets. It has purchased four systems that it uses daily in training and safety roles, he added. Two of them are at firing ranges, measuring mortar-crew accuracy.
Acoustics scientist Subramaniam Sadasivan had been working within India's Ministry of Defense on ways to passively learn about nearby aircraft when he saw a research paper referencing Microflown. In short order Sadasivan's project—called Environmental Acoustics Remote Sensing Station—had a Microflown sensor on a ship recording the sound of a drone overhead. He was impressed by Microflown’s technology and, now retired, continues to champion the firm's sensors in unmanned aerial vehicles.
This is not an academic exercise for Jacobs. "In my time as an observer in the Bosnian War I was shot at, but didn't know at first where it came from. I needed a couple of weeks [of harrowing experience] to know where the bullet was coming from," he adds. Microflown's device "can save lives."
Assuming the technology matches early sentiments, it could find new markets outside battlefields. Rich Christiansen, head of the American Institute of Aeronautics and Astronautics' unmanned aerial vehicle program committee, says it would also be useful for law enforcement when trying to locate shooters.