AuSIM3D® builds an audio simulation from four components: signal generation, sound source emission, wave propagation, and sound perception. 

• Signal Generation
  The field of signal generation is very large, mature, and well-established.  Today synthetic signal generation is achieved by one of three different models: frequency modulation (FM Synthesis), sample superposition (Wavetable Synthesis), and physically-based models.  Currently, AuSIM3D® contains some rudimentary FM signal generators and full support for the replay and modulation of sampled waveforms.  But the future of AuSIM3D® is in directly coupling physically-based synthesis to AuSIM's physically-based propagation models.  At present, AuSIM3D® can be interfaced with Stanford CCRMA's Synthesis Toolkit (STK) as well as NCSA's Vanilla Sound Server (VSS). 
• Sound Source Emission
  Proper modeling of how sound waves propagate away from its emitter is essential for realistic perception of the image.  While AuSIM plans major advances in sound source propagation models, AuSIM3D® already supports the most advanced models of any commercially-available aural simulation system.
• Sound Wave Propagation
  Simulating the propagation of sound waves through a complex 3D geometric environment is AuSIM's bread and butter.  Unfortunately, we are keeping you in suspense until the model is finished.  In the meantime, AuSIM3D® implements a distance model which assumes a constant propagation medium between sound source and sink. 
• Sound Perception
  Human perception is very difficult to fool, making this final stage the most important.  AuSIM3D® takes a listener-centric approach, implementing its own twist on head-related transfer function (HRTF) methods.  AuSIM's HRTF implementation is a hybrid between measured impulse responses and parametric physically-based models of the human hearing system.  The result of AuSIM3D® technology is a summary signal from the whole aural environment as it should be descending the listener's ear canals.  Most HRTF-based positional 3D audio methods are actually only two-dimensional ... depending on only the radial vector between a sound and the listener.  AuSIM3D® implements a near-field model, providing an approximate effect for sounds that originate within arm's length of the listener.

The AuSIM3D® technology is all original, built fresh from the ground-up leveraging a dozen years of experience with interactive, positional 3D audio.  While both AuSIM and AuSIM3D® are relatively new, the models comprising the technology have been refined through four generations.  Finally, it should be acknowledged that AuSIM3D® also leverages five decades of very excellent psychoacoustic and signal processing research. 

At the time of this writing, the AuSIM3D® API is still being finalized, and is planned to be published with AuSIM's acoustic simulation model within the next four quarters.  Don't fear however.  The AuSIM3D® technology is accessible through a wrapper of Crystal River Engineering's popular CRE_TRON "C" API.  Hence current users benefit from this elegant design under the hood.  The CRE_TRON API is supported by a dozen commercial applications and toolkits, as well as used in hundreds of user applications around the world.