The sound of a frog is known as a call and is often describedÂ as a "ribbet" or a croak. These calls differ widely between the many frog species, but they will usually fall into one of two categories: advertisement calls and alarm calls.
Advertisement calls are the loudest and are made by males in order to attract female mates. Alarm calls are intended to scare off attacking predators or male competitors for the same female. In this instance, these calls might also be described as aggressive calls.
Some frogs make their calls by compressing their lungs with their mouths and nostrils closed so that air rushes over the vocal chords and vibrates in the inflated vocal sac. Others simply use their vocal chords.