I am able to actually ID this species exactly due to the calls it makes, slightly slower and lower pitched than the Cope's Grey Tree Frog. Here is a link that provides sound files for the different calls that the Cope's and Grey tree frogs make: http://www.cmnh.org/site/ResearchandColl...
Found on the underside of the top of the above ground pool. (pool is currently down for repairs, and the frogs have spawned and have hundreds of tadpoles in the remaining water). We are waiting until they the tadpoles have legs and have morphed into frogs before repairing the liner and refilling the pool.
in the second picture you can see where the frog was hiding in early evening making it's calls.