I have four "waves" of chicks, as I had to get them over a few weeks to get all the breeds I wanted from our local farm store. The first ones were born Aug 1st, making them about 9 weeks. A few of them have a full on cluck, no cheeping at all, and one is still pretty much cheeping. My second set, which are a week younger has two that are clucking and three that are making higher pitched cheep-clucking noises. The next (two weeks younger than the first ones) set only one is slightly clucking, but she seems like she grew really fast anyways, so I guess thats why she's clucking early. My last two are five weeks are still cheep like babies. I think it varies a bit by chicken, but it seems around the 7 week mark is when their noises really started to change.