Guinea pigs make noises to communicate their feelings to other animals and humans.  Here are some of the sounds a guinea pig might make:

Cooing: Guinea pigs sometimes coo to their babies or to each other. This sound is a sign of affection. Some guinea pigs also use this sound for their favorite humans.
 
Gurgling: A sound like gurging is used by some guinea pigs to express happiness and contentment. Guinea pigs use this with each other and with favorite humans.
 
Squealing: This high-pitched sound is loud and is meant as a warning signal that danger is approaching. It’s also a sound of pain. On occasion, guinea pigs will use it to get attention too.

Teeth Clacking: When a guinea pig chatters its teeth, the animal is warning another animal to stay away. If the warning is not heeded, the guinea pig may follow with a bite.

No sound? If your guinea pig is being quiet, it’s probably sleepy, relaxed or just has nothing to say at the moment.