ATRAC

from The Free On-line Dictionary of Computing (8 July 2008)

Adaptive TRansform Acoustic Coding
ATRAC

   <algorithm> (ATRAC) An audio compression {algorithm},
   introduced by {Sony} for its {Mini Disk}, which relies on the
   masking of low-amplitude frequency components by temporaly
   adjacent high-amplitude components.  ATRAC consists of a
   three-band {subband encoder} (0...5.5, 5.5...11, 11...22 kHz)
   and a {MDCT} based transformation encoder.

   [Does Sony Minidisk use {ADPCM}?]

   (2001-12-13)

from V.E.R.A. -- Virtual Entity of Relevant Acronyms (June 2006)

ATRAC
       Adaptive TRansform Acoustic Coding (Sony, Digital audio, CODEC)