Adaptive TRansform Acoustic Coding(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)