I've understood that the sounds are in vp files. Look for the right file name and write it up. Then, rename your audio file as same name and paste it into appropriate directory. For example, if you want to replace sound "clusterboom.wav" with your own audio file, do following:
-Find the file with DMvpview. In this case, the file is in sparky_fs2.vp, under dir path data\sounds\8b22k\clusterboom.wav.
-Rename your new audio file "clusterboom.wav" (I don't actually know whether the game uses only name "clusterboom" or filename with extension "clusterboom.wav"; in the first case you could put in a clusterboom.mp3, clusterboom.ogg or whatever, but in the latter case it must be a wav file... Try and find out. *.wav should be the surest way to get it working...)
-paste your renamed audio file into your main FS2 directory under Freespace2\data\sounds\8b22k\clusterboom.wav, and it should override the same named file in vp's. At least that's how I've understood how FS2 works: first it checks the vp's, then the data dir.
(And, as kara kindly corrected, it does check the data dir first and
if it finds nothing it gets the files in vp instead... I somehow thought of it like the vp's would be "normal", but if there were same filename in data folder, that file would override the file that was in the vp's...

)
What kind of voice do you want to replace? Wingman messages? They exist in stu_fs2.vp and they are under path data\voice\personas\ and the replacing file should go to that directory in data folder.
I don't thing a table would be needed, as you'd need to put the files there anyway. So i'd suggest you create a mod directory named MetalDestroyerVoice or something like that and put your voice files there... that way you can more easily swap between custom voices and retail voices if you wish to.
That is, if you're using fs2_open... in retail fs2 the only way is the main data folder.