High-resolution audio

High-resolution audio, also known as High-definition audio or HD audio, is a marketing term used by some recorded-music retailers and high-fidelity sound reproduction equipment vendors. It refers to higher than 44.1 kHz sample rate and/or higher than 16-bit linear bit depth. It usually means 96 kHz (or even much higher), sometimes informally written as "96k", meaning a Nyquist frequency of 48 kHz, which is outside of the hearing range of any human ear.

There is no standard definition for what constitutes high-resolution audio, but it is generally used to describe audio signals with bandwidth and/or dynamic range greater than that of Compact Disc Digital Audio (CD-DA, informally CDs). This includes pulse-code modulation (PCM) encoded audio with sampling rates greater than 44,100 Hz and with bit-depths greater than 16, or their equivalents using other encoding techniques such as pulse-density modulation (PDM).

Although there is no firm definition, Sony describes high-resolution audio devices as those that deliver audio that’s clearer, sharper and more complex than other music sources and closer to the original.

File formats capable of storing high-resolution audio include FLAC, ALAC, WAV, AIFF and DSD, the format used by Super Audio Compact Discs (SACD).

One of the first attempts to market high-resolution audio was High Definition Compatible Digital in 1995. This was followed by three more optical disc formats claiming sonic superiority over CD-DA: DAD in 1998, SACD in 1999, and DVD-Audio in 2000. None of these achieved widespread adoption.

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