Digital Speech Standard (DSS) is a proprietary compressed digital audio file format defined by the International Voice Association, a co-operative venture by Olympus, Philips and Grundig. DSS was originally developed in 1994 by Grundig with the University of Nuremberg. In 1997, the digital speech standard was released, which was based on the previous codec. It is commonly used on digital dictation recorders. Modern phycoacoustical codecs that perform nearly as well at only slightly higher bitrates have led to this speech coding standard being less used in modern voice recording equipment.

AU is a file extension for a sound file format belonging to Sun, NeXT and DEC and used in UNIX. The AU file format is also known as the Sparc-audio or u-law fomat. AU files contain three parts: the audio data and text for a header (containing 24 bytes) and an annotation block.