Guinea pigs are very friendly creatures, with a lot to say for themselves. Firstly there is the very loud welcoming weep weep. They will make this noise to greet you, and to welcome the food you are bringing them. They will put so much energy into this squeaking that their ears will move up and down at the same time. These are happy guinea pigs.
Then there is the deep throaty rumble or purr. This is made when they meet a new guinea pig for the first time, especially in a boy meets girl situation. If there is any bickering between guinea pigs then this throaty rumble may be accompanied by some teeth chattering.
Then there is the background of chat as they communicate with each other as they feed, made up of little squeaks and chirps, no doubt talking about food!
When behaviour goes wrong
Guinea pigs are social creatures, and will rarely fight with each other. However, if there is not enough food around one dominant female may start to bully the others. If there is disagreement within a group of females it is important to provide several food bowls, and tubes to hide in. It is also worth considering introducing a neutered male who will take control of law and order.
If there is a lack of food, particularly a lack of hay, then dominant guinea pigs may start chewing the coats of the others. This is known as barbering, and the culprit will be the only one left with flowing locks! Barbering can also occur if the guinea pigs are bored. So provide them with plenty of hay and let them take lots of exercise and they are unlikely to start chewing each other.