SB AWE32 Developer's Information Pack
PART V 3D Positional Audio API
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Copyright
Creative Technology Ltd., 1994-1996
Version 3.00
PART V 3D Positional Audio API
Library Overview
The 3D Positional Audio Library provides programmers a low-level access to audio spatialization
algorithms implemented on the SB AWE32. The library provides programmers the ability to create and
move in 3D space basic audio spatialization objects such as sound emitters and receivers. The library
attempts to control the apparent location of sound emitters relative to a receiver by modeling a small set
of physical and psycho-acoustic phenomena.
3D Positional Audio Overview
The technology of spatial audio breaks down into two basic categories, depending on the techniques
employed to produce the spatial experience.
Passive Stereo Enhancement
Passive Stereo Enhancement systems are, as the name implies, methods for improving the three
dimensional nature of an already captured sound image, without any user control of apparent sound
position. A Stereo Enhancement system is any system which takes as its sole realtime input a two
channel stereo audio signal, and outputs a (hopefully improved) two channel stereo audio signal. The
systems may, of course, have controls which determine the degree of enhancement. These systems have
no possibility for real time positioning and controlled movement of sound sources, since they can only
accept a signal that has already had all of its components mixed together.
Parametric 3D Audio
In Parametric Spatialization, one or more monophonic channels are reproduced according to realtime
dimensional parameters specifying the position of objects in the soundfield. Unlike other techniques,
Parametric Spatialization determines the stereo audio image synthetically, based on realtime input.
Parametric Spatialization is thus interactive and user controllable.
Which 3D Audio Cues are most robust?
People can localize sounds in 3D space well, but in fact, a variety of consistent cues (or clues) are
required by our perception mechanism to determine where a sounds is coming from in three dimensional
space. Suprisingly, one of the most important perceptual mechanisms that we use to determine a sound's
location is head movement! Why this is true tells us a lot about what we can honestly expect from
synthetic spatial audio systems.
By far, the most robust cue for perceiving spatial location is "lateralization", or the ability to determine
whether a sound is on our left or right side. Even people who are deaf in one ear are fairly good at
lateralization.