MATING CALLS The croak of a frog or toad is the sound that a male makes so a female can find him and mate with him. Click the picture to hear this Spring Peeper. To make the sound, air is pushed into the mouth. The skin on the bottom or sides of the mouth swells up like a balloon. The sound starts in the voice box and bounces back and forth off the stretched skin. This makes the sound much louder. Click the picture to hear this American Toad. Every different kind of frog and toad makes its own special sound. You can hear the croak of each kind of frog or toad when you visit their page.