Session Title:	3D and Multichannel Audio
Session Chair:	Sean Olive, Harman International, Northridge, California, USA
Participants:	Jerry Bauck, Cooper- Bauck Corporation, Tempe, Arizona, USA, John Norris, Harman International, Northridge, California, USA, Brian McDowell, Microsoft Corporation, Redmond, Washington, USA
Sean Olive: While stereo will remain with us for some time, 3D and multichannel audio are now a reality. Content providers will soon have several choices for encoding their audio tracks in several different multichannel or 3D audio formats. Alternatively, in the near future some content providers will enable the consumer to interactively control in real-time where the sounds appear in space, and even adjust electronically the acoustics of the spaces around them, to match the plot and setting of the content. These sessions will provide an overview of the current and future multichannel and 3D audio encode/decode options available. While most Digital Versatile Disk (DVD) movies will be encoded in one of the current multichannel formats, the open format standard for DVD audio has to date brought forward three different proposals from the audio engineering community. Which one is best is a matter of some controversy. Ironically, the migration of multichannel content to the computer Desktop has been a catalyst for binaural-based 3D audio solutions. Given the limited desktop space and audio budgets of typical computer consumers, it is anticipated a large portion will not wish to purchase the additional speakers and amplifiers required to properly play back multichannel-encoded audio. A solution is to apply binaural signal processing to the decoded channels and simulate phantom or virtual images at locations where the additional speakers would normally be located. This can be done using headphones or two speakers using interaural-cross talk cancellation techniques. Several companies now license 3D algorithms that do this using programmable digital signal processors (DSP) or application-specific integrated circuits (ASICS), and there are even implementations that run natively on the central processing unit (CPU). Some content providers require solutions for real-time positional 3D audio for interactive games and software applications. With the much anticipated release of Microsoft's next version of DirectSound content providers can specify the co-ordinates in 3D space at where they want the individual sounds to appear. The signal processing required will be done natively on the CPU , although various 3rd party accelerators will be desired by consumers who want enhanced features and performance. John Norris: Research carried out since the 1960's indicates that the auditory localizing system is organized into preferred bands of frequencies, which are dependent on the angle of incident of the source of sound. Thus it is important when approximating the measured HRTF (Head Related Transfer Functions) to pay particular attention to these spatial localizing intervals. These preferred bands can be shown to be characterized by notches and peaks, caused by sound diffraction around the head and reflection caused by the torso and pinna. This diffraction and local reflections from the folds of the pinna cause peaks and notches to appear in the HRTF. Because the pinna's shape and its complex structure of folds vary for each individual, the HRTF is listener dependent, but nevertheless general spectral trends can be seen. It is known that these spectral trends enable different listeners to obtain spatial cues utilizing other individuals' HRTFs. Thus the peaks and notches convey spectral cues which help resolve the spatial ambiguity associated with the cone of confusion. It is also known that as the angle of incident sound changes, the location of the notches and peaks changes to reflect the change in the direction of the incident sound. An overview of current theory of spatial localization will be presented. Jerry Bauck: A new technique, which improves the quality of 3D audio when using loudspeakers, is described. The technique substantially enlarges the listening sweet spot without requiring unduly large low-frequency signal Amplitudes. While the technique is particularly well adapted to applications, which use a video monitor, it also provides an intriguing alternative to the conventional stereophonic loudspeaker pair. Brian McDowell will present Microsoft's current plans and direction concerning 3D and multichannel audio support in Windows and DirectSound. Topics discussed include current support, in software and hardware, for 3D audio in DirectX 5.0, as well as plans for 3D HRTF solutions and integrated multichannel support in future DirectX and Windows OS releases.

Biographies:

Sean E. Olive, Jerry Bauck, John Norris

Sean E. Olive SEAN OLIVE received a Bachelor of Music in 1982 from the University of Toronto, where he studied piano. In 1986 he graduated from the Tonmeister program at McGill University in Montreal, Quebec receiving a Master's degree in Sound Recording. From May 1985 to March 1993 he was a research scientist at the Acoustics and Signal Processing Group at the National Research Council, located in Ottawa. In March 1993, Mr. Olive joined the R&D Group of Harman International in Northridge, CA, as manager of subjective evaluation. His responsibilities include overseeing subjective testing of consumer, professional and computer/automotive audio products within all Harman companies worldwide. Mr. Olive has chaired and presented several papers at AES conventions, conferences, and workshops related to research on the perception and measurement of sound reproduction. He has published several of these papers in the AES Journal, for which two received AES Publication Awards in 1990 and 1995. In 1996 Sean received the AES Fellowship Award. Mr. Olive is a member of the AES Working Group on Listening Tests, and is on the Executive Committee of the Los Angeles section. Jerry Bauck JERRY BAUCK earned a B.S. from Kansas State University and M.S. and Ph.D. degrees from the University of Illinois, all in Electrical Engineering. His Ph.D. work was in space-based synthetic aperture radar. He has worked for Motorola in radar, acoustics, and signal processing and has consulted for various companies. He began early 3D audio studies in 1978 with Duane Cooper. Dr. Bauck is president of Cooper Bauck Corporation, an audio engineering and Transaural licensing concern. John W. Norris JOHN NORRIS completed his D.Phil (Ph.D.) in Mathematics at the University of Oxford in 1987. Since January 1993, he has been employed by Harman International. Presently he is helping develop Harman's VMAx virtual sound positioning technology. He has also worked on an active control system for noise and vibration cancellation. Before taking up his present position, he held teaching and postdoctoral positions at the University of Oxford and University of Birmingham in England. His areas of research interest include signal processing, nonlinear dynamical systems, and acoustics.

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