We had the same Problem, They Seem to get more Vocal when they are Bored, Or if they can hear you and think your coming to give them Treats.
Try giving them some more to do.
We bought a Fruit spike off the internet and have it dangling from the roof of the Run.. its about 20 inches from the floor, we put red or white cabbage on it, or 2 or 3 Apples, we have put all sorts on it. the chooks Love it, they spend ages pecking at it and it just swings around and around and they chase it, or wait for it to come back around to them, and then have another peck, its funny to see 6 or 7 of them in a circle waiting for it to swing their way so that they can have their turn hehe