Frogs don't have external ears like we do. Instead, they have an eardrum of sorts, called a tympanum, which sits just behind each eye. When sound hit the tympanum (essentially a thin membrane surrounded by a cartilage ring) it vibrates. This in turn vibrates a rod connected to the inner tympanum. The vibrating rod stirs fluid in the inner ear, and the resulting waves wash over tiny hair cells. These hair cells are connected to nerve fibers that transfer the electrical pulses to a part of the brain that interprets sound.
Amazingly, frogs also hear with their lungs. When sound waves hit the lungs, they're funneled directly to the tympanum (the frog's eardrum) through an air link. The difference in pressure between sound waves coming in from the external environment and those being funneled through the lungs is allows the frog to locate sound. This helps female frogs, for example, locate mates during the breeding season.
The air link between the lungs and the tympanum may also protect the frog's ears from its own calls, which can be nearly as loud as a jackhammer in some species (90 to 95 decibels). Specifically, the air link helps to equalize the pressure on the inside and outside fo the ear drum so that it doesn't rupture.
» MORE ANATOMY OF A FROG
