 | ||
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.
Contents
Definitions
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).
History
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.
Following the rise in online music retailing at the start of the 21st century, high-resolution audio downloads were introduced by HDtracks starting in 2008.
Further attempts to market high-resolution audio on optical disc followed with Pure Audio Blu-ray in 2009, and High Fidelity Pure Audio in 2013. Competition in online high-resolution audio retail stepped-up in 2014 with the announcement of Neil Young's Pono service.
Sony Corporation, the maker of the legendary Walkman® was granted registration of the trademark logo "Hi-Res AUDIO" and made their intellectual property available to the rest of the high-resolution community, as they come together to nurture this new market segment. Consumer audio products that came with the "Hi-Res AUDIO" logo indicate that the product meet the specification required for a high resolution audio product, as defined by Japan Electronics and Information Technology Industries Association (JEITA).
Most recently, Sony has reaffirm its commitment towards the development of high resolution audio segment by offering a slew of Hi-Res Audio products as it seeks to re-establish its leadership in consumer audio products.
Controversy
Whether there is any benefit to high-resolution audio over CD-DA is controversial, with some sources claiming sonic superiority:
and with other opinions ranging from skeptical to highly critical:
Business magazine Bloomberg Businessweek suggests that caution is in order with regard to high-resolution audio: "There is reason to be wary, given consumer electronics companies’ history of pushing advancements whose main virtue is to require everyone to buy new gadgets."
High resolution files that are downloaded from niche websites that cater to "audiophile" listeners often include different mastering in the release – thus many comparisons of CD to "special" releases are evaluating differences in mastering, rather than bit depth.
In the early days of Super Audio CD, a number of special remastered releases were published, and consumers expressed a preference for the SACD remasters. A scientific double blind trial, however, showed that by professionally producing a CD from the SACD master, individuals could not detect a difference in an ABX test. Notably, many people who perform their own unblinded listening tests do not match the decibel level of both audio sources, or guarantee that the CD version is produced from the high resolution version (to guarantee no mastering differences).
Most early papers using blind listening tests concluded that differences are not audible by the sample of listeners taking the test. Blind tests have shown that musicians and composers are unable to distinguish higher resolutions from 16-bits 48 kHz One 2014 paper showed that dithering using outdated methods (rectangular unshaped dither, rather than the industry standard triangular dither) produces audible artifacts in blind listening tests.