hi,
can you bear in mind that when making 2 or more differentiating signal noises, the main confusion for players in a game is tempo of the signal.
its fine to sit on the side and listen to 2 different electronic bells, but when you get in the water players are thinking "are we short or long". possibly low or high, but sounds like short and long is more suitable for this system.
so... make sure one signal is just a long, perhaps continuous sound, and the opposing signal broken into sharp short bursts.... easiest way to tell the difference quickly.
my thoughts only.
