In the usual "stereo" audio presentation, a partial soundstage consisting primarily of the front elements of the soundstage is created by two channels, either sampled from several microphones set in the original soundfield, or more often by a mixdown of many microphones placed both in proximity to the performers and out in the hall, to capture the "ambience". The information presented by the the two channels, in either case, is a small fraction of the information in the original soundfield. This fraction, additionally, is presented to the front of the listener. The presentation does not create an "envelopment" experience, where one is immersed in the original soundfield, as the information is not present. While some processors mimic the effect, such effects are not based on the actual venue, but rather on some hypothetical model of a venue.In "holographic" or "auralized" two-channel presentation, a presumed human "HRTF" (Head Related Transfer Function) is used to create an impression of sound arising from other than the front of the listener. This works well in headphones, or with interaural cancellation, for one listener facing directly ahead, and on the central axis between the speakers. This method can, with some difficulty, produce an immersive effect for one point in the soundfield, assuming that the subject maintains the proper head position, and the subject's head has an HRTF like that of the presumed functions. The ultimate form of this is, of course, "binaural" recording, where an actual head model is used to capture the information for one head location.Beyond two-channel presentation, one can think of analytically capturing an original soundfield to some degree of accuracy. This would require the use of many channels, perhaps placed in a sphere about the listener's head in the simplest form, requiring very high data rates (1000 to 10000 channels, perhaps) and creating a very high probability of influencing the soundfield in the space with the microphones and supporting metchanisms themselves. As a result, this technique is currently infeasable, and is likely to remain infeasable, for basic physical reasons as well as data-rate reasons, and actual analytic capture of the spatial aspects of a soundfield in this fashion is unlikely.
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