Acoustic Vector Sensor is a super small microphone which can hear and identify any sound.
A Dutch firm, Microflown Technologies, has created a micro device which listens for various sounds emanating from a battle field, such as gunshots, mortars, screams and warplanes. The Acoustic Vector Sensor is smaller than a match head and consists of two platinum strips.
Popsci reports more on the working of this device:
By measuring the mechanical movement of individual air particles, as opposed to sound waves as a whole, the device can not only pinpoint the origin of sniper fire or approaching aircraft, but detail their make and model, as well.
While there are other technologies that can trace the origin of sounds, most of them require considerable infrastructure to support these technologies. Because of the minuscule size of Acoustic Vector Sensor, it can easily be carried by a soldier, giving him first hand information on the source of the sound.
The device is already being tested by armies of a few countries.