| Chair's note Dear Reader, Welcome to this educational CD-ROM on audio coding artifacts, prepared by members of the AES Technical Committee on Coding of Audio Signals. This is the first educational/tutorial CD-ROM presented by the AES Technical Council on a particular topic, combining background information with specific audio examples. To facilitate the use of high-quality home playback equipment for the reproduction of the audio excerpts, the disk can also be played back on all standard audio CD players. We hope you find this a useful feature. Compared to other "classic" disciplines in audio engineering, the field of perceptual audio coding is still a rather young technology, combining elements from digital signal processing, coding theory, and psychoacoustics into one system. It is, however, mostly the psychoacoustics that frequently leads to questions from nonexperts ("how does that work?") and sometimes is even perceived as some kind of "black magic" within the coder. Since many of the members of the AES Technical Committee on Coding of Audio Signals have been confronted with such questions, the idea of an educational publication on this topic soon found broad support within the group once its concept was formulated. It was Markus Erne who proposed the production of a CD-ROM that would offer nonexperts some guidance on the background and sound of the perceptual effects a listener is likely to be confronted with when working with compressed audio signals. Initiated at a Technical Committee meeting at the AES 106th Convention in Munich in 1999, the idea eventually took more than two years and quite a number of Technical Committee meetings to be fully developed and implemented within the committee, finally leading to this publication. Of course, such projects do not happen all by themselves. They are the fruit of extensive behind-the-scenes hard work by motivated individuals. So let us first of all congratulate Dr. Markus Erne for his outstanding contributions. He inspired us and drove this project to its completion. He spent many hours coordinating the contributions, setting up the electronic infrastructure and, finally, assembling the CD-ROM master. Our thanks also go to all the Technical Committee members whose contributions facilitated the success of the project by preparing and reviewing both the tutorial chapters and the audio excerpts found on this disk. We would also like to extend our thanks to all the AES officials who have been vital in making things happen, including the officers of the AES Technical Council and the staff of the AES publications office. Final thanks go to the European Broadcasting Union (EBU) and Philip Laven, its technical director, who kindly gave permission for the use of some audio excerpts from EBU's legendary "SQAM" (Sound Quality Assessment Material) recording. We hope that you will find this CD useful and that it may be the first of a series of similar electronic publications by the AES Technical Council. Jürgen Herre and James D. Johnston, cochairs AES Technical Committee on Coding of Audio Signals August 2001