of both 2-channel and 5.1-channel sound. Direct Stream Transfer compression was standardized as an amendment to the MPEG-4 Audio standard, ISO/IEC 14496-3:2001/Amd 6:2005 (Lossless coding of oversampled audio), in 2005. It contains the DSD and DST definitions as described in the Super Audio CD Specification. The MPEG-4 DST provides lossless coding of oversampled audio signals. Target applications of DST are archiving and storage of 1-bit oversampled audio signals and SA-CD. A reference implementation of MPEG-4 DST was published as ISO/IEC 14496-5:2001/Amd.10:2007 in 2007. Copy protection SACD has several copy protection features at the physical level, which made the digital content of SACD discs difficult to copy until the jailbreak of the PlayStation 3. The content may be copyable without SACD quality by resorting to the analog hole, or ripping the conventional 700 MB layer on hybrid discs. Copy protection schemes include physical pit modulation and 80-bit encryption of the audio data, with a key encoded on a special area of the disc that is only readable by a licensed SACD device. The HD layer of an SACD disc cannot be played back on computer CD/DVD drives, and SACDs can only be manufactured at the disc replication facilities in Shizuoka and Salzburg. Nonetheless, a PlayStation 3 with an SACD drive and appropriate firmware can use specialized software to extract a DSD copy of the HD stream. Sound quality Sound quality parameters achievable by the Red Book CD-DA and SACD formats compared with the limits of human hearing are as follows: CD Dynamic range: 90 dB; 120 dB (with shaped dither); frequency range: 20 Hz—20 kHz SACD Dynamic range: 105 dB; frequency range: 20 Hz— 50 kHz Human hearing Dynamic range: 120 dB; frequency range: 20 Hz—20 kHz (young person); 20 Hz—8-15 kHz (middle-aged adult) In September 2007, the Audio Engineering Society published the results of a year-long trial, in which a range of subjects including professional recording engineers were asked to discern the difference between high-resolution audio sources (including SACD and DVD-Audio) and a compact disc audio (44.1 kHz/16 bit) conversion of the same source material under double-blind test conditions. Out of 554 trials, there were 276 correct answers, a 49.8% success rate corresponding almost exactly to the 50% that would have been expected by chance guessing alone. When the level of the signal was elevated by 14 dB or more, the test subjects were able to detect the higher noise