In case it’s of use or relevance, there are easier ways of reversing PAL speed up in an audio file.
Admittedly it’s command line, but there are gui interfaces available.

Eac3to has a simple flag -slowdown which does it, so just add that to the end of the command line.

Example to convert a file called ep1.ac3 to a new file called ep1fixed.ac3 you would type:

eac3to ep1.ac3 ep1fixed.ac3 - slowdown

You can also add the required bitrate as a further option (e.g. -384 or -448). I’m not sure what the default is.

I use this for any PAL speedup reversal, although I won’t always go to AC3. You can just use filename ep1fixed.wav if it want uncompressed output, or if you get the required plug ins installed .dts .aac etc.

Hope that’s of help to someone.

Also, vobsub is a quick little program for changing frame rate of subs (i.e. Removing PAL speed up)