The string %AudioFileName% is just a special string defined by TextAloud. TextAloud should replace that string with the name of the file. If it isn't working that way there is a bug.
One thing to try though ... click Tools -> TextAloud Options. On the TextAloud Options panel, click the Article Options tab. Under the Article Titles section, there is a checkbox labeled "Use Document name as article title when loading text from documents". Is that checkbox selected? If not, try selecting it. Then, If you load a text file named "Chapter 1 - Why was Sin Permitted.txt" into TextAloud, the Article Title will default to "Chapter 1 - Why was Sin Permitted". When you write an mp3 file from this article, the name of the file will be "Chapter 1 - Why was sin permitted.mp3", and should match %AudioFileName%.
Does that help with the problem?
If it doesn't help you may have found a bug. Duplicate this problem creating a small audio file. Once the audio file has been created, go to the TextAloud main window, click Help -> Open Data Folder, and locate the files TextAloudMP3.dbg, TextAloudMP31.dbg, TextAloudMP32.dbg and TextAloudMP33.dbg. Attach these files to an email and send them to me at
jim@nextup.com