The maud file extension is associated with the Amiga MAUD audio format, developed by Electronic Arts and Commodore in 1985. The MAUD is used for an 8 or 16 bit Amiga sound format. Most likely obsolete.
Psion 8-bit A-law. Used on Psion SIBO PDAs (Series 3 and similar). This format is deprecated in SoX, but will continue to be used in libsndfile.