There seems to be a lot of request on how to convert Audible files to MP3. So, this is a guide on how to convert it with free software.
1. You will need GraphEdit. It is part of Microsoft's DirectX SDK. You can google it and download it too.
2. You need to have AudibleManager installed. It includes the DirectShow filter you need to decode Audible in DirectShow.
3. Run GraphEdit. Select "Graph | Insert Filter..." menu. Expand the "DirectShow Filters" node.
4. First, add "File Source (Async)". When the file dialog shows up, browse to the .aa file.
5. Then, add "Audible Words Codec".
6. Connect the output from "File Source" box to the input of the "Audible Words Codec" box.
7. Actually, there is no easy way to output to MP3 or WAV in GraphEdit. A lot of third party software would have their own filters to do that. However, you can output to an audio-only AVI, and then convert the AVI to WAV, MP3, or whatever.
8. Again, go to the "DirectShow Filters" node (see step 3). Add "AVI Mux". Connect the output from "Audible Words Codec" to the input of "AVI Mux".
9. Add "File Writer". It will ask for your file name. Type in "xxxxx.avi". Connect the output of AVI Mux to the input of "File Writer".
10. Click on the run button on the tool bar (triangle) to run the graph. When it stop, you will get an AVI file with uncompressed audio. Then you can simply convert the AVI to MP3 or WAV in most audio conversion software.
