The AVR file extension is a data format known as Audio Visual Research File. AVR files were developed for use on Apple Macintosh computers. They were specifically, used for the older 680×0-based Atari ST computer systems.

SPHERE (SPeech HEader Resources) is a file format defined by NIST (National Institute of Standards and Technology) and is used with speech audio. SoX can read these files when they contain μ-law and PCM data. It will ignore any header information that says the data is compressed using shorten compression and will treat the data as either μ-law or PCM. This will allow SoX and the command line shorten program to be run together using pipes to encompasses the data and then pass the result to SoX for processing.