AU is an audio format developed for Unix-based or Sun Microsystems machines. Since its creation, AU has become the default audio file format for storing sounds on most Unix platforms.
Also, AU files contain three separate components, namely a 24 bytes header, an annotation block and the actual audio data.
In order to be able to make their own custom AU files, users will have to select and use a dedicated multimedia app with support for this particular audio format.
Audio converters will allow their users to convert audio files to AU and also enable them to assign a personalized filename to the resulting AU file.