Ps3 – League Play Class Problems

You guessed correctly, you are receiving two audio signals. Lets step back and think of how split screen sound works. Assume you and I are playing split screen. If someone shoots at me, I have to hear it (even though your character may not be in range to hear the gun shots). So essentially two audio feeds are being fed through the speakers.

Now what your discussing is clearly a bug (I have a feeling this won't be the last one thats found on an obviously incomplete game). Both yourself and your friend are essentially receiving a unique audio feed of the in-game chat. In order to prevent this from happening you must mute your friend and he must mute you. Here is a ps3 forum post describing the problem and solution. If this doesn't work try plugging a mic into one of the controllers and sending audio chat to the mic (not the speakers) or actively mute all players who join the game. It looks like a patch may be coming for the issue.

Hope this helps

Finally found this on Ubisoft forums:

This is a known problem with the game that the developers are currently investigating. In the meantime, please try this workaround:

• Login to multiplayer and set up your profile.
• After setting up the profile, logout of multiplayer and start a single player game.
• Save the game in singleplayer, then log back in to multiplayer mode.
• Your profile should now be saved correctly.

I didn't try the workaround yet as I'm too addicted to the multiplayer mode right now. I'll try this later and accept the answer if it works.
I put it here anyway. Who knows if it can be of any help in the meantime!
Tried the workaround which didn't work for me... :(
Let's wait for a patch then.