What is a AU file?
Audacity project audio chunks
Audacity, an open source audio editor, breaks long tracks into small pieces so it can edit them more efficiently. Thus, when you save an Audacity Project File (.AUP), Audacity will automatically create a _data folder that has the same name as the AUP file and breaks the longer audio file into smaller chunks that have the .AU extension. Thus, when Audacity opens up the AUP Project File, it loads the individual AU files in the correct sequence automatically. The user should not move or rename and AU files in the _data folder.