In DOD:S "K" is the default voice chat key. Set your own in the keyboard options. Then, go in game and hold it down and speak. If that doesnt work I have other things to discuss however, its not worth typing if all you need is the key bind.
This probably has such a simple answer if we were able to look at it. Call up a geeky friend of yours if you can, it will probably be solved post haste.