That's what I'm worried about as well - the hearing part. But chickens have good hearing. They would have to be a long away apart to NOT hear each other. I'm not sure though. I haven't done it before.
So, we are toying with the idea of a bachelor pad, as well. From my understanding, this only works if the roos can't see the little princesses on the other side - or they will fight.
I'm hoping someone else will weigh in on this. I know debate exists over bachelor pads and I would like to hear...