I've also been using the ImpCTF sounds for awhile, great script. It's been awhile since I downloaded them but I do sort of remember it not working correctly at first. I can't remember what I did to fix it though.
Anyway in case anyone wants it here's my slightly modded version of his flag sounds. It's just a combination of ImpCTF and T2 flag sounds and some of the default sounds. Some of the original IMP sounds were annoying as *dance* from what I remember nd these sounds make more sense to me. At least it will show you the right folder to put them in and you can easily change the sounds to whatever you want (I think they all have to be .wav files but I dunno, I'm not actually good at this *chocolate cookies* haha).