AU, Audio File (.au)
The AU Audio file format
The AU file was introduced by Sun Microsystems. This file format facilitates the storage of audio files, usually in three sections: a header with maximum strength of 24 bytes, an annotation block of variable length and the audio data itself. Primarily, this file format is used by Sun or other Unix-based machines, but it can be opened with various audio programs.
Technical details of AU files
The AU format is associated with the µ-law logarithmic encoding that was endemic to the SPARCstation 1 hardware, where SunOS revealed the encoding to application programs through the /dev/audio interface.