No sure everyone really knows why, so is it related to "loony-bin audiophiles" or is it simply
psiyhoacoustics?
"Hearing is not a purely mechanical phenomenon of wave propagation, but is also a sensory and perceptual event; in other words, when a person hears something, that something arrives at the ear as a mechanical sound wave traveling through the air, but within the ear it is transformed into neural action potentials. The outer hair cells (OHC) of a mammalian cochlea give rise to an enhanced sensitivity and better[clarification needed]frequency resolution of the mechanical response of the cochlear partition. These nerve pulses then travel to the brain where they are perceived. Hence, in many problems in acoustics, such as for audio processing, it is advantageous to take into account not just the mechanics of the environment, but also the fact that both the ear and the brain are involved in a person’s listening experience."
What is perceived can be different from the actual physical sound, because hearing is affected by other stimuli and memory and expectation, and everyone are subject to this. To the extent that it does not help that you know how this works, you will still be affected and may hear things that actually does not exists, and what you think you hear is percieved as real.
This is caused by the way hearing works. Acoustic sound enters the ear and physical hearing mechanisms, then there is a psychoacoustic part that interprets this acoustical-mechanical input - frequency/tone, loudness, location/direction. Then there is a psychological part, where the brain tries to make sense of the sound - what the sound is, decoding of spoken words. This last part searches for solutions that are most likely, and uses other information in this process. Such as if a spoken word is partly masked, the missing details will be filled in so that it matches something that is likely. This comes into play when listening for differences that are barely audible, or not present at all. If there is no difference, the brain fills in using all sorts of other non-acoustical cues, and creates an illusion of a sound that simply does not exist.
I am not an expert on hearing and perception and psychology, but someone is, ask them of you want to learn more about how hearing actually works.
To experience how this works, you can do some experiments. Find something you know from a technical analytical perspective is likely to sound the same, but still you suspect there is a difference. Listen to both, find how they sound different, continue to focus on those differences. When you are very sure you have identified how they sound different, now try to identify which one is playing in a abx. The differences suddenly disappear. Now, how can this be - either your hearing had you fooled, or blind testing does not work.
One practical way to test this:
- Install foobar with foobar abx plugin.
- Find a music sample in flac/lossless.
- Encode sample in 320k lossy format, use a newer codec, mp3/aac/ogg.
- Compare flac vs 320k until you are sure you can hear the difference.
- Then try to abx the files, to get a reliable verification.
The exact same method can be used to do controlled listening tests of electronic devices - dacs, amplifiers.