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Terminology of Sound
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3D Sound
Refers to the fact that sounds in the real world are three-dimensional.  Human beings have the ability to perceive sound spatially, meaning that they can hear where a sound is coming from, and where different sounds are in relation to their surroundings and in relation to each other.  There are three main pieces of information that are essential for the human brain to perform these functions:
ITD, or Interaural Time Difference, means that, unless a sound is located at exactly the same distance from each ear (e.g. directly in front), it will arrive at one ear before it arrives at the other.  For example, if the sound arrives at the right ear before the left ear, the brain knows that the sound is coming from somewhere to the right.
IID, or Interaural Intensity Difference, is similar to ITD.  It says that if a sound is closer to one ear, the sound's intensity at that ear will be higher than the intensity at the other ear, which is not only further away, but usually receives a signal that has been shadowed by the listener's head.  Sometimes referred to as the ILD or Interaural Level Difference.
Spectral Difference, a sound bounces off a listener's shoulders, face, and outer ear, before it reaches the eardrum. The pattern that is created by those reflections is unique for each location in space relative to the listener. A human brain can therefore learn to associate a given pattern with a location in space.
Since 3D sound consists of two signals (left and right ear) it can be rendered on conventional stereo equipment, preferably headphones (because of the clean separation of the two signals).  The 3D sound produced by a direct path AuSIM3D® system may be combined with sound reflections to create a very high level of realism and immersion in a sound space.

3D Sound is also referred to as positional sound, spatialized sound, and vectorized sound.  Because the AuSIM3D® technology calculates sound path vectors, AuSIM's literature typically refers to 3D sound as vectorized.
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