3D Audio and Acoustic Environment Modeling

                          A 3D audio system has the ability to position sounds all around a listener. The sounds are actually created by the loudspeakers (or headphones), but the listener's perception is that the sounds come from arbitrary points in space. This is similar to stereo panning in conventional stereo systems: sounds can be panned to locations between the two loudspeakers, creating virtual or "phantom" images of the sound where there is no loudspeaker. However, conventional stereo systems generally cannot position sounds to the sides or rear of the listener, nor above or below the listener. A 3D audio system attempts to do just that.
                      A lot of commercial audio products are described as having 3D capability, but in fact there is great disparity between the various technologies in use. Unfortunately, many of the weakest products are marketed with the most exaggerated claims. For example, a number of stereo multimedia speakers are marketed as having "3D" technology. These speakers incorporate a simple circuit that has the effect of widening the perceived soundfield of a stereo recording. That is, the sound images that would normally extend to the locations of the left and right speakers are widened to extend beyond the speakers. These systems should more properly be called stereo enhancement or "widening" systems. They have no ability to position individual sounds around a listener, nor do they have the ability to position sounds behind, above, or below the listener. We use the term 3D audio to describe a much more sophisticated system than can ideally position sounds anywhere around a listener.
                      Even within the field of what we would consider to be true 3D technology, there is a wide range of technologies in use, with corresponding variation in the performance and cost of the products. Compounding this is the fact that even the best technologies are subject to unavoidable limitations that guarantee that the performance of 3D audio will always fall a bit short of the marketing claims. This has created some confusion in the marketplace. Nevertheless, 3D technology is rapidly improving, thanks in part to the increasing availability of inexpensive computational power.

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