N >> 2: Multispeaker Display Systems for
Virtual Reality and Spatial Audio Projection

Perry R. Cook
Department of Computer Science (also Music)
Princeton University, Princeton, NJ, USA
1 Georg Essl, 1 Georgos Tzanetakis, 2 Dan Trueman
1 Department of Computer Science
2 Department of Music
Princeton University, Princeton, NJ, USA

Abstract
This paper describes multispeaker display systems for immersive auditory environments, collaborative
projects, realistic acoustic modeling, and live musical performance. Two projects are described. The sound
subsystem of the Princeton Display Wall project, and the NBody musical instrument body radiation response
project. The Display Wall is an 18' x 8' rearprojection screen, illuminated by 8 highresolution video
projectors. Each projector is driven by a 4way symmetricmultiprocessor PC. The audio subsystem of this
project involves 26 loudspeakers and server PCs to drive the speakers in real time from soundfile playback,
audio effects applied to incoming audio streams, and parametric sound synthesis. The NBody project
involves collecting and using directional impulse responses from a variety of stringed musical instruments.
Various signal processing techniques were used to investigate, factor, store, and implement the collected
impulse responses. A software workbench was created which allows virtual microphones to be placed around
a virtual instrument, and then allows signals to be processed through the resulting derived transfer functions.
Multispeaker display devices and software programs were constructed which allow realtime application of
of the filter functions to arbitrary sound sources. This paper also discusses the relation of spherical display
systems to conventional systems in terms of spatial audio and soundfield reconstruction, with the conclusion
that most conventional techniques can be used for spherical display systems as well.

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