Originally Posted by JohnVV
Evil_Bert you do know that that link is to a windows .exe
Yes ...... FFS, I *can* read!!!
The "aa" mplayer option you mentioned isn't a file format, it's a video output driver - specifically the AAlib driver that plays video in ASCII-art format (though one wonders why anyone would want to do that).
The link I included does cover GoldWave as well as his method - there's value in the comments, too.
AFAIK, the problem with Audible (.aa files) is they're DRM-encumbered (Apple's FairPlay, apparently) - the player apparently does a web lookup to verify credentials before unlocking the file and only runs on Windows or Mac ..... and you thought iTunes was bad.
But if the chap paid for the files, I don't see why he can't try to play them on Linux after conversion ..... or maybe try Wine or a Windows Guest OS in, say, VirtualBox if that doesn't work out.