Same thing happens to me. You can use this temp fix I use when it starts doing this. Press the PS3 Button and goto settings (in the game) then goto accessories settings, finally goto Audio Device settings and select nothing in input and default in output. Then press OK go back and reselect you turtle beaches, and press OK. This worked for me a little while, then I had to do it again.
Most mikes need to do this to get the little speaker to show up when you talk. It is a really annoying major flaw in the game and I hope they fix it soon.