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Re: spatial separaton

The group in which I am working is researching a particular artificial environment, that created (or not) by home "surround-sound" entertainment
systems. When we set out to make a recording, whether it is a background
for a talking-head news report or a music performance in a concert hall,
want to know what choices will improve the "quality" and what choices
degrade it.

Our approach so far has been to follow the stimulus-response paradigm, but
we have been using several methods to try to get reponses that are
meaningful. We have watched the discomfort of industry colleagues who
developed headphone spatialisation schemes that performed very well when
experimenter asked about localisation, but suddenly performed badly
when people started asking about "realism". If we ask subjects to scale
this elusive "realism" or "goodness" and also scale the other perceptually
relavent attributes of the differences between stimuli, then we hope that
we can eventually come up with some optimum points on attribute scales
then at least have somethng to aim at when developing recording and

The trick in this approach is to identify the perceptually relavent
attributes for a given population of stimuli. I am in the midst of trying
to interpret the spaces spit out by multidimensional scaling, and a
colleague is doing well using Rasch repertory-grid-technique.

Of course the stimuli have facets of programme type, recording
environment, and many facets of recording technique. There are also
facets of the playback environment that must be considered, such as
possible absence of the centre-front loudspeaker and large loudspeaker
frequency-response differences between front/rear/centre-front. The set
of most perceptually relavent attributes may differ between a Bach
tocatta and a Brandenburg concerto, and may differ between the
Brandenburg concerto conducted by Pinnock and conducted by Rattle.
The results of tests will never necessarily be generalisable to any
programme with a different facet profile.

Douglas McKinnie
Institute of Sound Recording
University of Surrey