Quoting raptor mommy saves:" At what age do babies find their voice and start playing with the volume? LO has been screaming, shrieking ... [snip!] ... almost constant and my poor ears are bleeding.... and my nerves are so on edge. He is teething like crazy too. *post and run*"One of mine started doing it between 6 and 7 months. The other more recently started at 8 months. I always hear it and think something is wrong. Then they look at me and laugh. Crazy girls!