Hummmmmmmmmm

The last couple nights when the house gets quiet I've been noticing a humming sound or someone singing softly.  I about drove myself crazy trying to figure out what it was Wednesday night.  I went all over upstairs trying to see if a toy was on.  I asked Bri if she heard it, she said no.  Tonight, Thursday, the same thing happened.  I finally realized Bri is humming herself to sleep!!  She about made me crazy trying to figure out where in the world that noise was coming from.