Some voices are cool, while others make you feel like somebody turned the temperature all the way down. A cold voice over is all about those reads that make you feel the character's got ice in their veins.
A cold voice is what you need when characters have to deliver the flat, emotionless affect that's practically an embodiment of the cold shoulder. Thera are voices that chill you to the bone because there doesn't seem to be anything there other than a slight undercurrent of disdain and aloofness. If your script calls for this type of read, you should check out these voices to find what you're after.
There are many types of situations that may call for a distant voice reading. Characters in video games and movies sometimes hit a rough patch and tell off others very coldly; other times there are characters that are so detached and impersonal that you wonder if they've got copper wiring under their skin. In some cases, you'll want to see the transformative power that a product may have on a character who starts off chilly, but gradually warms up and shows more emotion.
The cold voice tends to be more on the slower end of things (as contrasting with the motormouth, who's overexcited all the time). Their measured, slow tones can almost make you feel the stalactites attached to each deliberately-uttered word. Brr!