Kurt may be right. Here is a link to a website at the University of Florida that gives information on Florida frogs and toads. The link is the page for the squirrel tree frog and there is a link about midway down with a sound file.

http://www.wec.ufl.edu/extension/wil..._squirella.php

Check out the calls for the Pinewoods tree frog as well. My only hesitation is that it is pretty large for a male of either species.

It's large enough to be a barking tree frog, but they don't typically have smooth skin. Perhaps you could listen to all the calls on the site for treefrogs (including the cuban, even though the toe pads doen't look large enough) to rule out any from the southeast U.S.