Hi
On 24/04/2011 19:11, Helmut Oellers wrote:
...modern computers are also clever. Today nothing is unaccountable if we
know the formula and all variables.
That's a BIG assumption - and given the essentially chaotic (in the mathematical sense) nature of
the Universe, wrong. We are now pretty certain that nothing is that predictable and that that idea's
basically (old) Science Fiction - we have moved from E. E. "Doc" Smith's "Lensman" universe ( where
ultimately intelligent beings could predict everything because they knew the complete starting
conditions and laws of the Universe) to the Discworld universe of Terry Pratchett where one flap of
a Quantum Weather Butterfly's *** wings can change the course of the entire Universe (and confound
even the Gods).
However, at WFS we have a chance for avoiding that problem. All we need is
including the playback room properties into the synthesis. By this way
becomes possible, subtract the additional detours of single wave fronts in
the playback room.
Even in theory, this can only be done to a limited extent as you don't have sufficient foreknowledge
of the state of the room acoustics, only that of a model with significant simplifications on things
like surface properties of materials and, perhaps more importantly, air movements in the space -
which cannot be predicted given the chaotic nature of the system. In practice, the limitations
caused by finite speaker separation and the two dimensional nature of most extant WFS systems mean
that the cancellation would only be valid at low frequencies. The perceptual effects of having the
disruptive effects of playback space reflections cancelled at low frequencies and not at higher ones
would need to be subject to listening tests, as would the 2D/3D conflict before we could give any
kind of definitive answers - there might well be situations (or source materials) for which
attempting cancellation of playback space acoustics could actually be worse than the effects of the
playback space acoustics themselves.
Never conventional procedure will be able to that,
because direct wave, first reflections and reverberation inseparably merge
together in the transmitting channels. Thus, the playback room unavoidably
remains the disturbing component in transmitting chain. No chance exists for
true spatial audio by that way, thereby. And no chance exists for
reproducing the source distance correctly in the traditional way.
I think this is unnecessarily pessimistic and ignores the capabilities of the human brain to fill in
missing details and/or ignore incorrect/inconsistent cues just so long as a sufficient subset of the
cues presented are both (adequately) correct and consistent.
On the other hand, if "true spatial audio" is intended to mean the recreation of an original real
acoustic acoustic event (concert, airshow recording, whatever...) as it would have existed as a
percept by a human attending that event, well, that's not going to happen with any of our systems
until (and if) we can do direct brain recording and stimulation to a level of detail that current
fMRI working is only barely beginning to hint at. That's because that percept does not just consist
of the stimulation of our ear drums by the sound waves but also all the inputs from the other senses
and, moreover, not just at that point in time but also previous to that.
Dave
***
http://en.wikipedia.org/wiki/Quantum_Weather_Butterfly#Quantum_Weather_Butterfly
--
These are my own views and may or may not be shared by my employer
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