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Each node of InTheMix is split across three computers in a
client/server configuration.
The first computer maintains the InTheMix client application,
a custom application that monitors the tracking
instrument, controls the aural simulation, and triggers audio events.
The second computer is an AuSIM GoldServetm system running the
AuSIM3D® audio simulation service.
The third computer is also an AuSIM GoldServer™ system,
but running NCSA's Vanilla Sound Server (VSS),
which synthesizes sound via parametric algorithms.
Digital audio is piped from the synthesis server to the rendering server over a
fiber-optic "light-pipe" using Sonorus' StudI/O
digital audio interface. The client and servers communicate via
low-latency serial packets, either USB or RS-232. Inter-node (client
to client) communication is also serial.
All computers in the InTheMix project are Intel-based systems
running the Microsoft Windows 2000 Professional™ operating
system, specially tuned for real-time operation.
All audio streams to and from the AuSIM server are fully digital. Analog
conversion is completed in an external unit, utilizing 24-bit conversion,
isolated from the digital noise.
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The headsets integrate a tracking
sensor with circumaural, closed headphones and a noise-canceling boom
microphone. The headsets are designed and manufactured by AuSIM from
the highest-quality German-made
Sennheiser components. Circumaural headphones surround the ear's
pinnae (ear-lobe) providing more consistent centering for more consistent
auditory localization. The closed headphones occlude the physical
world by attenuating ambient noise by 15-18 decibels. A headset control,
specially-designed and manufactured by AuSIM, optimizes the dynamic range
for localized audio and interfaces the microphone and headphones to the
digital converters. All analog signals are protected from noise
with professional, balanced interconnects.
Position-tracking is controlled via AuSIM's low-latency AuTrak™
tracker interface software library. AuTrak™ supports all
tracking instruments from Polhemus, Ascension, InterSense, Logitech, and
Fakespace, as well as several others. The specific tracking system
depends on installation-specific parameters.
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