Croaking Frogs

One of my very favorite parts of summer is sleeping with the bedroom windows wide open and listening to the croaking frogs.  For the most part, we can only hear them right after Leroy has irrigated (which he hates to do) in the field that surrounds his parent's house.  They croak so loud that it sounds as if they are right outside the window.  We get to see many toads in our yard but I don't think these are the ones croaking.  I think the sound comes from frogs... not toads.  (I could be wrong... it happened once before.)