The reason that they are called chorus frogs is that they have all different tones of “voices”. Some high some low, even though they are all the same species. They are also able to change their color. If you look under my constructed wetland tab (http://www.puravidaaquatic.com/index.php/constructed-wetland/) there is a picture with six of them sitting on a leaf. They are all brown except for the back one which is green.
This is what I hear when I open the front door in the early spring.
Or walking up the driveway…
Sometimes it is fairly loud :-)