Yeah, my assumption. Sorry. Regardless, the BG2 method does not work in BG1. This is why it's of utmost importance to clearly specify which game you are talking about when posting in a multi-game forum.

I assume the BG2 method was editing the CHARSND.2DA table? As far as I recall or ever discovered, BG1 was supposed to be nothing more than entering .wav files into the Sounds folder.

That's correct. I can only guess that it not working for you has something to do with being installed in the Windows protected folder structure. I've never had issues like you describe.

BG2 classic doesn't require messing with 2da, anyway.

I didn't try new soundsets on BG1, but if the soundset is seen on selection window, it's recognized all right.
Try extracting without wavc>wav?