When Little Z was a baby (she's only 2 1/2 now, so not so long ago) I would go to her when she was crying. Then, sometimes, after I went to bed and was trying to go to sleep, I would think that I was hearing her crying. I would check on her, and she was sound asleep. But I would still hear her crying. Even when, logically, I knew she was not crying and she was sound asleep, I would hear her. It was clearly some sort of auditory hallucination, but I could never talk myself out of it. I could look at her and see her sleeping, and the second I looked away, I heard her crying. I would fall asleep sometimes and feel like I could hear her crying in my dreams.
Now, with these little chickens, a similarly odd thing has happened. Laying in bed the past couple of nights, I could hear the chics chirping. The really crazy thing about this is that they live in the Organic Machine House, a.k.a. the Barn, and I live in the house, and (it being winter) all of the windows are closed. There is just no way I could actually hear them. But of course, I heard them none the less for knowing that I couldn't hear them.
I could tell myself that my husband's nose must be whistling, but I still fell asleep to the mild sounds of baby chickens.