Todd Plummer asked about frogs that sound like a person running a finger along a comb.  Those are the Chorus Frogs, genus Pseudacris, and there are several species.  In Gwinnett County you have the Northern Chorus Frog, Pseudacris triseriata, and possibly the Southern Chorus Frog, Pseudacris nigrita, but being above the fall line, the more likely is the Northern.  I'm sure that these frogs have been broken up into other subspecies by now, but this is how it was taught to me back in the stone ages of 1990.  There are some great tapes available on learning frog calls - 'Voices in the Night' is a good one...

Mary Elfner
Savannah