on the localisation in the superimposed soundfield - Hauptmikrofon ...

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In terms of the localisation model to be depicted below, it is assumed that direction
and distance are inseparable qualities of spatial hearing.
It is striking that in the area of visual perception many genuine perception models are
known, whereas this is hardly the case for auditory perception. From a
neurophysiologist and information theorist’s viewpoint this is incomprehensible, as no
fundamental differences exist between the eye and ear’s function as receptors of
information. Nonetheless, there are two reasons for this deficiency. Firstly, due to
commercial reasons a much larger interest exists for technical applications of visual
perception models (data reduction by means of appropriate source coding for image
transmission, e.g. replication of pattern recognition principles with the help of
classification processes or adaptive filters). Secondly, pattern recognition and
association principles are more clearly recognisable in visual compared to auditory
perception.
At this point, two perceptual models – one from the visual and one from the acoustical
domain – shall be briefly delineated, since they contain mechanisms also featured in
the new localisation model.
Replicating the visual system, MARKO 1974, 1978 proposed the so-called “layer
model” for pattern recognition, which he based on considerations of system theory
(see Figure 14).
The “layer” is meant to symbolise a layer of neurons on which one should imagine
excitation patterns. The hatching of the layer is supposed to indicate that threshold
elements are present at the output, so that only suprathreshold signals are passed on.
In terms of system theory, this arrangement corresponds to a multi-stage threshold
logic. The non-linearity given by the threshold elements is crucial for the
classification process. Within the discrete stages, local filtering is carried out
(orientation-selective filter, edge detection), the subsequent non-linear distortion (e.g.
maximum detection) enabling the classification. It is worth emphasising the multistage
principle of this classification model.
The pattern characteristics are discriminated and forwarded one after the other. They
complement each other after having passed through all layers, thus forming the
complete pattern. This is also a feature of the association model.