Developed during the Jedi Civil War, this device was designed to emit a powerful sonic pulse. It was very useful for scaring off or stunning various wildlife. The emitter proved indeed lethal for the several species of firaxan shark patrolling the waters near Republic's secret Hrakert Station.
Normally it would have a very limited range, but in underwater environments like Manaan the signal would travel much further. It was designed to be attached to an envirosuit, and used when wildlife go too close.
The Jedi Revan found one in the station and it proved to be a vital piece of equipment in order for him to reach the Star Map on the ocean floor.