This site was prepared by Malcolm and Kent Slaney, in conjunction with Richard F. Lyon and Roy Patterson, based on designs by Ivana Andjelkovic and Jensen Hsiao.

Most of the content for this site started life as the "Apple Hearing Demo Reel." This video tape was created in 1991 and demonstrated the correlogram model of auditory perception using a number of examples. At the time correlograms could be created in near real-time using the Cray-X/MP supercomputer at Apple. But this four-processor machine wasn't quite fast enough to guarantee real-time, so the videos were created one frame at a time and inserted one at a time to the end of a Beta video tape. This process took about 6 seconds per frame because each frame required the machine to back the tape up, get the tape up to speed, insert the new frame, and stop the tape.

The current videos were created using the same code (MacEar). The audio and video frames were converted into MPEG-4 videos using ffmpeg and qt-faststart. The OOG videos were created using ffmpeg2theora.

When referencing these videos, please use the original publication: Malcolm Slaney and Richard F. Lyon, Apple Hearing Demo Reel, Apple Computer Technical Report #25, Cupertino, CA 95014 (c) 1991. Now available at

For questions or comments, please email