When Maddy shouts/screams/screeches, we put our finger up to our lips and say shhhhh. She's learned that this means be quiet and will often do it back to you. Unfortunately she will also shout/scream/screech louder in order to do the finger/shhhhh trick again. Not sure it's really working, but it's kind of cute. Here she is shhhh herself in the bathtub.