There is an orb inside its mouth. When it hops, the orb bounces all over and makes a ringing sound.
It emits high-frequency cries that people can't hear. Once it starts, it can cry for an awfully long time.
This Pokémon gave me an excruciating headache when it seemingly cried out without making a sound. Perhaps there are some sounds that the human ear is simply incapable of hearing.
