Northern Cricket Frog (Acris crepitans) 2015-5-9 Patuxent Research Refuge, Anne Arundel County, MD

Highly variable.
Aw, nuts! Had a page that gave Northern and Southern sound files for comparison and can't find it now. grrr
This will do - ID by sound, here:
http://www.virginiaherpetologicalsociety.com/amphibians/frogsandtoads/frog-calls/Northern%20cricket%20frog%20-%20track13.wav
another sound example:
http://www.in.gov/dnr/fishwild/files/cricket2.MP3
Northern Cricket Frog fact sheet:
http://www.dec.ny.gov/animals/7120.html