Gorillas communicate by making a soft purring sound that's been labeled the belch vocalization. This sound is often heard when gorillas are comfortable, such as after a meal or during a period of rest.
Gorillas make a variety of noises when threatened. Screaming, screeching and roaring are common noises heard when a gorilla fears a predator, is about to engage in a fight or becomes angered at another gorilla.
Female gorillas have distinct noises they make when communicating with their young. A soft bark-like noise or hoot sound is common when a mother gorilla wants to discipline a baby or communicate with a young gorilla.