Snakes can hear through their jaws by picking up vibrations on the ground. The vibrations are then sent to their brain via the inner ear, translating into a sound.
When a snake feels a vibration with its jawbone, it is sent into the cochlea first and then transmitted directly into the brain. Snakes do not possess an eardrum, but they do have a fully-formed inner ear connected to the jawbone. They can increase their hearing precision by burying themselves into the ground. This affects the way their jaws move, similar to a ship's movement in the water — the more stable the jaw is, the better it can detect sounds. Snakes are also equipped with special sensory organs in their skin, which allows them to detect vibrations along their entire body.