Each month an industry expert highlights a topic of importance to the AES community. Listen, Learn, and Connect with advances in technology and best practices in audio.
In its commonly understood meaning, “high-resolution audio” is that group of digital formats whose sampling rates and bit depths exceed those of the CD (44.1 kHz and 16 bits). But these formats are only delivery modes. Much more important are a different set of questions: what is meant by a high resolution signal; what bandwidths, time resolution, and dynamic range are important to our critical perception; what is needed technically to achieve very high signal quality considering the influence of the entire processing chain on the outcome; and why should sample rates with bandwidths well beyond the known human auditory limit of about 20 kHz (for airborne transmission) matter?
Research and debate on these questions has gone on for the last 30 years, since the early days of digital audio. The debate played out very interactively with the continuing advance of technology, as digital systems became much more capable of high performance quality. Today, high resolution is a well-established part of both professional and high quality consumer audio, and the answers to the “why” of sound, its technical reproduction, and its relation to auditory perception are better understood.
The papers I've included here are from AES publications, conferences, and special JAES issues as well as outside resources on definitions and standards. They are meant to be widely exploratory on the above questions. As the briefest introduction to the topics covered in greater depth below, high res audio aspires to achieve the highest integrity in reproduced (audible) sound. Signals should retain, among other properties, clarity, depth, separation of closely spaced images, and the absence of additive or modulating noise or distortion, especially smearing of nearly time-coincident signals. The technical and processing aspects critical to this goal, together with relevant auditory science, effective capture and delivery, and listening tests are considered in these papers.
The first three papers present a wide overview, the next ten focus on design considerations inclusive of psychoacoustic principles, and the last two deal with perception and perceptual testing. Also note the high res special issue in JAES this month (May 2019).
Curator: Vicki Melchior
Vicki Melchior has served as vice-chair, then chair of the AES Technical Committee on High Resolution Audio since its inception in 2000. She is a member of AES Technical Council and DSP committees, and an Associate Technical Editor for the Journal. Additionally, she is guest editor for the May 2019 AES Journal, a Special Issue on High-Resolution Audio.
Vicki's background is centered in signal processing and scattering theory, comprising a Ph.D. in biophysics from Yale University, postdoctoral and subsequent work in biophysics (X-ray diffraction studies), and then radar technology. With lifelong involvement in music and audio, she entered the audio industry in 1995, working initially on Sonic Solutions' pro audio workstation, then consumer DVD Audio ICs and signal processing. She currently maintains an independent technical consultancy focusing on high quality DSP, A/V software, and acoustic room correction.