Working with the human ear: the proper evaluation of audio equipment incl. amplifiers

[Macjager]

Alan
Some days I feel that I am sitting in a university class, striving to get a joint degree in common sense/audiophilia (even if there is such a thing as audiophillia...).

The question I have relates to the "addition" of tone controls after the fact, ............

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[CSawyers]

This is a somewhat late addition to this exceptionally interesting thread, and I hugely enjoyed Alan's examples of the effect of time delay in modifying perception. The only one I absolutely nailed was the 3Hz shift in frequency from 440Hz; even with 2 seconds delay this was absolutely clear, but as an amateur clarinetist I have a very good ear for pitch.

But there is a fundamental difference between the way the ear/brain and eye/brain systems work. There are some things they absolutely have in common:

1. They have extreme dynamic range - 12 orders of magnitude typically
2. They are exceptionally sensitive. The dark adapted eye can detect 3 photons per second from a point source. The silence adapted ear is tuned to just not hear Brownian motion of air molecules

But there are differences:

1. They eye/brain has a highly adaptive system of colour perception. This was demonstrated by Edwin Land (the guy who founded the Polaroid Corp) in his Retinex theory of colour vision, a word he coined as a combination of Retina and (visual)Cortex. In a series of landmark experiments he demonstrated that colour perception was based on a rapid evaluation of what was white in a scene, and all other colours are renormalised to this perceived white. Thousand of hits on Google for anyone interested
2 A good example of this is that you still look flesh coloured whether in sunlight, incandescent light, or even yellow sodium light from street lights. Perception of the colour of clothes is similarly reslient to lighting

This was the reason that the two orange images were particularly difficult to distinguish even with a very short delay.

As far as I know there is no aural equivalent of Retinex. Different mechanisms seem to be at work, with a strong evolutionary element. Is that twig snapping in the forest lunch, or am I in fact lunch? I need to locate its direction, and make fine judgements in real time. By contrast the eyes, being in the typical carnivore configuration on the front of the head have more to do with hunting and need insensitivity to lighting (dappled forest, in snow, in dark, in mist) in locating and chasing prey.

Craig