Prevent the pirates from sounding the alarm in Far Cry 3

Pirate Outposts in Far Cry 3 have at least one alarm box

If the enemies sound the alarm it will alert all pirates in the area of your presence

If you manage to get close enough to the alarm box without being seen, you can disable it

Note that shooting an alarm will NOT disable others in the same outpost. Manually shut down an alarm to disable them all.