The Sonic emitter was 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 lethal for the several species of Firaxan sharks patrolling the waters near the Old Republic's secret Hrakert Station on Manaan.
Normally it would have a very limited range, but in underwater environments such as on Manaan the signal would be amplified. The weapon 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.