Perceptual Audio Codecs
"What to Listen For"

Identifying the artifacts of lossy audio coding

Welcome to this educational package on audio coding artifacts, prepared by members of the AES Technical Committee on Coding of Audio Signals.

Perceptual audio coding is ubiquitous and perceptual audio codecs like MP3 and AAC are widely known. It has fundamentally revolutionized the way how we transmit, store and consume music, enabling applications like Internet streaming and downloading of music. The field of perceptual audio coding combines elements from digital signal processing, coding theory, and psychoacoustics into one system. It is, however, mostly the psychoacoustics that frequently leads to questions from non-experts (“Is this signal really intact?”) and sometimes is even perceived as some kind of “black magic” within the coder.

Perceptual Audio Codecs - What to Listen for

To educate users and listeners, the AES Technical Committee on Coding of Audio Signals (TC-CAS) has created educational material on “Perceptual Audio Codecs – What to Listen for”. It comprises tutorial information on the principles and limitations of perceptual audio coding technologies, as well as curated listening examples to educate and train listeners to identify possible audio coding artifacts.

Originally published as a CD-ROM in 2001, the material has been updated in content and functionality and been released as “The Second / Web Edition” for its 20th Anniversary in 2021. After the Web Edition has initially been exclusively available as an AES membership benefit, it is available free of charge to the general public since February 2023 for the 75th Anniversary of the AES, by courtesy of the AES and its Technical Committee on Coding of Audio Signals.

A brief overview over the tutorial’s enhancements and features is provided in this promotional video:

A more extended presentation of the tutorial content can be found in a related research colloquium event of the German AES section.

We hope that you will find this material a valuable resource for education and listener training and that it may contribute widely to the knowledge of the interested community. The educational material is available in two forms:

If you want to link to this useful resource, please use this permanent link:

Jürgen Herre (TC chair) and Sascha Dick (editor)
February 2023


Our thanks go to all the authoring Technical Committee members whose contributions facilitated the success of the project by preparing and reviewing both the tutorial chapters and its accompanying audio excerpts. Furthermore the generous support of the Fraunhofer Institute for Integrated Circuits (IIS) for the conversion of the existing material to the new web format is acknowledged. Moreover, we appreciate the support of International Audio Laboratories Erlangen, a joint institution of Fraunhofer IIS and Friedrich-Alexander-University Erlangen-Nuremberg, for hosting this resource. Finally, thanks go to the European Broadcasting Union (EBU) and David Wood, who kindly gave permission for the use of some audio excerpts from EBU’s legendary “SQAM” (Sound Quality Assessment Material) recording.

Technical remarks

Some mobile device browsers do not support browsing websites on the device’s local file system due to security considerations. This can limit the usability of the downloadable version on smartphones and tablets. Therefore, it is recommended to use the online version of the tutorial on mobile devices, preferably via a WiFi network to reliably provide sufficient transmission bandwidth.

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