HypetheSonics’ DAP database is a set of TI PCM4222 measurements from some of today’s higher-quality digital audio players that are being generated in partnership with SoundExpert.org. In addition to measurements of conventional audio test signals, such as sine waves and square waves, the algorithm assigns each DAP a quality score (Df median) by computing the difference between input and output waveforms based on real music. Simple synthetic test signals are not representative of real music and can give the false impression of accuracy by, for example, masking noise floors or other errors with a single loud tone. By providing complex, realistic test tracks, it is possible to discriminate between the various devices – even between those that show comparably small levels of THD+N for conventional test signals.