In true communication, signaling comes under the control of the conscious cortex rather than the subconscious emotional system. Chimps employ a rich variety of gestures and facial expressions to keep in touch with each other, and more importantly, there is intelligence behind the exchanges that makes for a level of understanding unseen elsewhere in the animal world. This sort of communication ability is what makes chimps appear far more socially advanced than any other animal. They may have a simple repertoire of noises and body language, but the intelligence with which these signals are used and interpreted makes a big difference. Only recently has it been realized how well chimpanzees can communicate.
Some chimps even develop their own special signals.
These observations indicate that chimps are the most intelligent communicators in the animal world, even compared to other highly social species such as lions, wolves and monkeys. Highly social animals also need to be able to mentally model the social world of their group, remembering such things as who is dominant, who is bad-tempered, and what actions are likely to follow a particular grunt or screech. A chimpanzee may have a deep understanding of the world and the brain power to model both physical and social relationships, but that knowledge stays locked away in the gray background of the memory banks until roused by events actually happening in the chimp's presence. Perhaps chimps also invent their own personal noises, maybe using particular grunts to mean certain things. But such personal noises are not as obvious as gestures to human observers.