Yes, this hobby & the goal of audio reproduction is the creation of an illusion - an illusion that gives us enough audible cues to satisfy our ever-vigilant auditory processing. Much like we watch television, videos or movies which offer us enough believability to allow us to forget their limitations & become engaged with the content - this is where the emotional connection then begins. If there isn't enough believability we are constantly aware of the medium & it's portrayal - when we are bored by the sound, it's a sure indication that this believability is missing or less convincing
Let's forget about the psychophysical aspect of the ear mechanism & focus on Auditory Scene Analysis or ASA. This is the area of study, first started by Bregman in 1990 or so, which is concerned with how we make sense of the vibrations of the eardrums & create an auditory scene from these signals. Much like we create a visual scene from the impact of photons on the rods & cone cells in the eyes, we create an auditory scene from the two streams of electrical signals coming from both ears.
Now, when you think about it, this is a highly complex & interesting problem that the brain has to try to solve - to continuously create a fully realistic, moving auditory scene that maps the auditory objects in that scene & follow their change through time. In other words close your eyes & listen - you will hear & be able to locate all the sonic objects around you, including the size of the room, etc. just from the electrical waves being generated in the ears. Think about it - this is the equivalent of sitting at a corner of a swimming pool & being able to use only the waves hitting this corner to sense how many people are in the pool, where they are & where they're moving to, what they're doing, how big the pool is, etc.
The idea of ASA seems to have its genesis in trying to answer the question that the "Cocktail Party Effect" gives rise to - how do we follow one conversation among all the other conversations & noise at a party. The audio signals from all sources are hitting the ear at the same time as the audio signal from the conversation so how do we isolate & associate the signals that belong to just the followed conversation from among all the rest i.e how do we form an auditory object & follow it in the face of changing signals & changing surrounding auditory signals?
How the brain does this is being teased out in ASA & other areas of sound research. The auditory processing happens whether we are listening to the real world or to the signals from our speakers which are attempting to create an illusion of an audio performance or audio event
We perceptually ascertain audio objects in what we hear by the brain processing that we perform on the signal. The perception of these audio objects occurs because we seem to cross correlate particular signal markers which we associate with that particular audio object - spatial location, timbre, temporal coherence, & amplitude all seem to play a role - let's call these some of our perceptual factors for identifying this object. So, the interplay & relationship between these factors are the rules or schema or models that is the study of ASA. If these rules are adhered to in the audio playback system then we have a believable illusion - the more the rules are diverged from, the less believable the illusion.
Now, one thing about digital audio - because it is based on mathematics & is almost infinitely adjustable, it has so many new ways to diverge from these rules & introduce new audio anomalies that we have never heard in the real world - things like digital filter ringing spring to mind. When we encounter a new audio anomaly that we haven't met before we tend to be subconsciously confused as we have no biological model to fit it to & we are not consciously aware of what is wrong, just that we want to turn off the playback or are bored by the sound & our attention drifts. I suspect that this occurs more often than we would like to admit & may well be where the disagreements arise from - between those that intuitively (Or explicitly know this) & those who believe that measurements tell us everything ?
This part is something I wrote before which continues from the thoughts above (so forgive some of the repetition to what's above):
Yes, it's already been stated here but is worth repeating - what we hear is a construct of our brain processing. Fundamentally, there is not enough data in the signals that are picked up by the two ears to fully construct the auditory scene - we need to use all sorts of pattern-matching, extrapolation, experience of the behaviour of sounds in the real world (biological models of sound), sight, etc. to generate the fairly robust auditory scene that we continuously do.
One of the important points that comes from the research is that we are continually processing the auditory data & updating our best-guess auditory scene by decomposing, analysing & comparing the auditory signal stream & comparing it to already stored auditory models of the world
People who interpret psychoacoustics as being the illusional part of hearing & what makes it untrustworthy are completely missing this fundamental point - psychoacoustics is what allows us to make sense of the jumble of pressure waves impinging on our eardrums. It's what allows us to pick out the auditory objects, such as the bassoon in the orchestra & be able to follow it's musical line through a performance or be able to switch to listening to the string section.
Stereo reproduction is itself a trick - a trick that uses some learned knowledge about psychoacoustics to present an acceptable illusion of a real auditory scene. However, not knowing the full rules/techniques that our brains use in psychoacoustics somewhat hampers this goal of realistic audio reproduction. As a result, we can find that small discoveries are stumbled upon which audibly improve matters in a small way but we have no clear explanation yet for how they are working at the psychoacoustic level.
Without this knowledge of psychoacoustic rules, we are stumbling around using unsophisticated measurements & I believe, incorrect concepts about the limits of audibility. A lot of the improvements that I hear reported in audio are about increased realism, increased clarity, etc. - in other words they are no longer about frequency/amplitude improvements - they are improvements in other factors which our psychoacoustic rules are picking up on & we are perceiving as more realistic. Or, maybe they are small changes in freq/amplitude that currently are dismissed as inaudible but further knowledge about psychoacoustic workings may well reveal them to be audible when part of the dynamics of music & not when tested in a lab with simple tones?
