the sound you are hearing is the /aroo command that makes a sound comparable to a 'Werewolf' howling.
to my knowledge the command when executed by a member or other low ranking player the resulting sound effect is only client side. however high ranking staff can execute it for every player currently in the game.
the above reason has no conclusive evidence behind it, it is just my understanding.
you will also find many other similar commands that are just for fun such as- /kouen /migas /nyeh, etc...
these are commands some would label as 'Troll' commands that are simply there to spice things up.
