Using the same technology as bomb or artillery deployable mines, the sub-munitions each consist of an ultra- sensitive microphone, a small actuator to orient the mic for maximum sensitvity, a battery, possibly a solar cell, and a relatively small radio transmitter. Either included with the package or as a separate drop/launch is a pair of larger units with high precision GPS devices, and much more powerful transceivers.
During deployment, the submunitions are scattered over a large(ish) area, and they wait a while, then send a pulse in sequence so the larger units can triangulate them. After the pulse, they go into listening mode. They transmit any sound back to the larger units, which analyze them for any human caused noise. Based on timing and localization of the microphones, the devices should be able to pinpoint individual noises. This information can then be transmitted back to headquarters.
This is primarily intended to operate as a rapid deployment search and rescue aid during major disasters such as earthquakes or avalanches that leave a large number of people trapped below the surface. In these cases, the mics would be scattered fairly densely in order to gain the most sensitivity.
They might also be viable for sea or land based searches for lost individuals, although clean-up would be difficult. In that case, a wider scatter could be used, since the individuals are typically going to be more able to respond. In addition, each mic might have a small audio circuit that instructs anyone who can hear it to yell out.
Ideally in almost any SAR application, these would have to be deployed before human searchers got into the area, hence the rapid deployment from fighter or bomber aircraft, which should be able to reach any disaster area in a very short period of time.
Finally, of course, they could have military applications in tracking the movement of enemy forces.-- MechE, Oct 27 2012 Acoustic Detection and Triangulation http://en.wikipedia...iki/Gunfire_locator [MechE, Oct 27 2012] http://www.sardog.e...r_sar_datasheet.pdf Acoustic detection of buried survivors. [MechE, Oct 27 2012] Obligatory pedantry: unless they are used for warfare, microphones and other sensors do not qualify as 'munitions'. I think the word you're looking for is 'payload'.
I'll return with my verdict on the whole idea. I need to think it over.-- Alterother, Oct 27 2012 Yeah, but sub-payload-itions doesn't have nearly the same ring to it.-- MechE, Oct 28 2012 I like the idea, although by happenstance if not intent it resembles the air-drop sonar bouy grids used by various navies since the Cold War. [+]-- Alterother, Oct 28 2012 random, halfbakery