There are not any species of frogs that absolutly require a "buddy" but whites do seem to appriciate it more than other species.

http://picasaweb.google.com/mynameisMnM/Amphibians#5268737306242394962

Also, I am going to have to disagree with bradtort, my frogs are extremely loud. If you to my site http://freewebs.com/kapoktree under videos you can hear their call. I have my frogs housed in the basement and I can hear them all the way upstairs.
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A room of herps.
www.freewebs.com/kapoktree