Writing application: Nandub v1.0rc2
Writing library: Nandub build 1852/release
And even worse:
Writing library: XviD 1.2.0.dev47 (UTC 2006-11-01)
Nandub is ancient and quite awful in my opinion. It was written as an alternative to VirtualDubMod, which is an alternative to VirtualDub...
Both Nandub and VirtualDubMod always had a lot of problems with AC3: Nandub not being able to correctly set the number of channels, adding tons of junk into the file; it cuts the stream right in the middle of a frame, adding junk to the end of one part and the beginning of the next, as well as at the beginning of the stream if there is a A/V delay that needs to be calculated. And besides, AC3 audio gets split across interleaves, no matter what interleave parameters you use.
I don't think that this is a problem with your version of AC3 installed, but just in case you didn't update recently, go to the AC3 website
and download and install the latest version of AC3 filter... Just in case, you might also download AC3file.
If the buzzing sound appears again, you can still play them correctly with VLC, or, if you own these movies, consider updating your rip settings to H264 instead of the crude XviD. Handbrake
is the best tool for this, if you decide on this approach but can't get the hang of it, I'd be happy to share a few tips