Audible audio format is used for digital audiobooks released by Audible. It is basically a DRM protected .mp3 file, hence you need a DRM removing tool to get the original .mp3 back. You can find some utilities that offer this kind of options.
Convert Audible audio to Compressed audio and music file, mp3 songs or ringtones.
We have found 2 software records in our database eligible for .aa to .mp3 file format conversion.
Articles and other information relating to aa into mp3 conversion:
How to convert Audible AA audio books to MP3 - Removing DRM protection from Audible audiobooks
Microsoft Windows software - convert aa to mp3 on Windows
A DRM remover and media converter
Convert from aa file format
The tables with software actions are a good pointer for what a certain program does with various file types and often may give users a good hint how to perform certain file conversion, for example the above-mentioned aa to mp3. However, it is not perfect and sometimes can show results which are not really usable because of how certain programs work with files and the possible conversion is thus actually not possible at all.
A program for removing DRM protection from multimedia files