Your pullets are now mature, and will be laying soon. This is a time when you will normally hear new sounds coming from them during the day. They vocalize, and chat with each other, and do the egg sound after they or another lay an egg. Some will get downright noisy. I had an ancona hen who used to spend 2 hours every morning stomping around the coop screaming at the other hens. She made more noise than any rooster could ever do. I have always enjoyed when the hens talk to each orhter or chatter when going about their day. I can usually recognize the voice from some of my girls before I see them.