Hmm. Ok. According to weapons.tbl, sound "162" should be playing. I see similar "numbers" for the sounds of other weapons. Must admit I'm confused, because the names of the weapon sounds have nothing to do with those numbers as far as I can see in either sparky_fs2.vp or corefiles_twilight.vp. I mean, I've even found the sound that should be playing. It was in corefiles_twilight.vp, and it is called npw2.wav in the data\sounds\8b22k directory.
EDIT: Found GalEmp's tutorial on modding and tables. That was somewhat enlightening. I've never done any of this before, but if I had to guess, there needs to be a custom sounds.tbl in addition to all the others Goober provided?
Beh. I may try my hand at it if no one else beats me to it, but not tonight. I've got a 5-week old daughter driving us both a little batty. I just came upstairs for some quick stress relief before rejoining the fray.