Hippos use their sounds to express dominance, establish territories, maintain social bonds, and convey various emotions or intentions. For example, a low-intensity grunt may indicate contentment, while a loud, aggressive roar could signal a challenge to a rival. Their complex vocal repertoire allows them to express a wide range of emotions and intentions, from greeting group members to warning off potential threats. Additionally, hippos use infrasound to communicate over long distances, both in water and on land.