Originally Posted by QueueCumber
What is much more difficult to measure are differences in how the same effects are processed/percepted by different people.
Indeed this is so. Humans learn and adapt, and it different people do it differently.
In my PhD research in the early '60s I was able to train listeners to believe that 0 interaural time difference (ITD) was not "center". All that was required was exposure to a laterally displaced abstract visual image on a CRT that supposedly tracked the auditory image - the visual image dominated the perception and subjects simply did not notice the discrepancy. After less than an hour of this "contradictory" experience a purely auditory localization exercise showed a displaced perception of "center". The aftereffect could last for more than an hour but retraining to zero ITD was possible in less time. At the time, psychoacoustic experimenters assumed that zero ITD was a definitive perception of center localizations.
In a much more complex way we adapt to rooms and to an impressive extent are able to "listen through" them to discern important qualities of voices and instruments in live experiences and loudspeakers in reproduced experiences.
Some of the discussions that I am reading assume that this is a "linear" cause and effect process. To a computer it is, but we are humans. We are barely able to model very basic perceptual dimensions with simple signals, much less interpretations of complex three-dimensional sound fields created artificially by two stereo speakers and a band or orchestra.
Behind it all there is an "Elephant in the Room" issue that has not, by my observation, been discussed. Strongly worded opinions about this or that in audio generally ignore the effects of hearing degradation. “I heard it, therefore it is real and true” is often assumed. It has been known for many decades that exposure to loud sounds causes temporary and then permanent hearing loss – the lost ability to hear low-level sounds. We also lose the ability to hear high frequencies. So, the combined effects of noise exposure at work and play, and age (presbycusis) reduces the information reaching our brains, and therefore our abilities to discern timbral and spatial (the ears may be different) subtleties and differences. When we go to our neighborhood audiologist for a “hearing test” it is based only on our ability to understand speech. It has nothing to do with discerning the small differences among pieces of high-performance audio gear. As discussed in Section 3.2 in the 3rd edition, within the audiologist’s interpretation of “normal” hearing it is possible to observe substantially degraded ability to judge sound quality. The opinions are real but not consistent in repeated exposures to the same sounds.
But then there is the recent discovery of something called “hidden hearing loss”. This can happen at any age, with or without accompanying audiometric threshold shift. The effect is binaural, affecting one’s ability to discern direction and to separate multiple sounds that coexist. The most common real-life example is when we have difficulty carrying on a conversation in a restaurant – the cocktail party effect, which takes me back to my advisor when I was a beginning PhD student. Chapter 17 describes some of the effects, and all of them bear on our perceptions of stereo soundstage properties. So, what any one of us perceives, may or may not be relevant to others.
I stopped participating in listening tests around age 60 because at Harman we not only track the subjective evaluations of loudspeakers, we also track the statistical performance of the subjects. I was not performing as well as I used to, so I retired from the “trained listener” population, and now any opinions I have are my own. But, all is not lost. Having spent 50 years at subjective/objective relations in loudspeaker performance, I now put more trust in a good set of anechoic measurements than in my own on-the-spot subjective evaluations.
Meanwhile, all that said, the 9.4.6 channel system I now have is sufficient to send chills down my spine when it is fed a good recording or movie. And the soundstage and imaging I hear are up to my highest expectations - when it is fed a good recording or movie. But that is me . . . in my room.