I was reading 10 Groovy Guinea Pig facts today just so see what literature is out there...here is a list of the sounds they make and their meanings incase anyone wants to know...if you already know thats awesome.

Guinea pigs are very vocal, and they can produce many different sounds all of which have different meanings. Some of the most common are:-* Wheeking a whistling noise which Guinea Pigs use to express excitement (e.g. at feeding time) or to help locate other Guinea Pigs.
* Purring a bubbling noise which expresses contentment. A deep purr is employed by the male (boar) when courting.
* Rumbling a deeper sound used to express dominance, fear or anger.
* Chutting a noise made during pursuit by the pursuer.
* Whining an noise made during pursuit by the pursuee.
* Chattering gnashing of the teeth used to raise a warning.
* Squealing a high pitched squeak in response to pain or grave danger.
* Chirping a bird-like noise which may indicate that baby Guinea pigs (pups) want to be fed. It may also be employed when a Guinea pig is stressed.

If anyone else has other sounds their guinea pigs make, feel free to share