I hear you. This is one of those things that is hard to believe, i.e. that someone can hear distortions that we ourselves think is an impossibility. There is fortunately science behind this but one that is not well known outside of industry and research.
The key here is understanding the concept of a trained listener. No, I am not talking about self-appointment "golden ears." I am talking about listeners that have gone through training and verification of their listening ability to be well above general public and that includes audiophiles. A great published example is that of work for Harman in their loudspeaker research through controlled listening tests. See this example:
http://seanolive.blogspot.com/2008/12/part-2-differences-in-performances-of.html
See how much better the discrimination and ability to identify artifacts are among trained listeners compared to other groups. Assuming that high-end audiophiles are represented by the "audio reviewers" the ability of trained listeners is about 5 times better!
How did that magic come about? As I mentioned, it is through specialized training. Fortunately Harman gives away that software and you can try to a) test your own abilities and b) become trained:
http://harmanhowtolisten.blogspot.com/
The software is like a video game in that it starts easy and progressively gets more and more difficult. The concept is simple: you are presented with an original track and another that has been modified by a single filter/EQ changing the frequency response. When the "Q" (bandwidth) of the filter is large detection is easy as it impacts so many notes. But as it gets narrower, less of the music spectrum is impacted and the job gets hard.
I remember running that test when it first came out. I got to level 2 or 3 and could go no further. Pretty disappointed.
So I practiced some and then gave it up. Fast forward a year or two later and I was at Harman with Dr. Sean Olive presenting us the same test in one of their reference testing rooms. Here is a picture of Sean and you can faintly see the How to Listen software output on the projection screen:
What you don't see is behind me which is a dozen high-end audio dealers some of whom are acousticians who had come for this training.
Sean started the program at level 1 and everyone got the answer right more or less to level 2-3 as I had originally. But the moment it went above that, I and Sean where the only ones who could guess correctly. I think I got to level 6 before I failed. That bit of training had made a noticeable difference in my abilities. My happiness on that front disappeared when Sean continued with utmost ease giving the right answer to levels 7,8, 9, etc. I mean he was not even trying! I asked him what the minimum requirement was for someone to become a trained listener and he said level 12. :eek:
After the event finished, I had all of the dealers come to me and ask me how I did what I did. They were amazed at it and to them it was like magic. From then on, and to this day when I run into them at shows, they consider me to have great ears even though I consider myself a failed attempt compared to trained listeners at Harman.
Now, the tables would be turned if we were talking about hearing non-linear distortions. Again, another story.
The year is 1998 and I am at Microsoft and was given the audio/video codec team to manage. I figure I better learn what they are doing and compress some files into 128 kbps MP3. After some 30 years of being an audiophile I thought it would be a walk in the park to hear artifacts in it. To my shock and horror, I found the sound to be as good as the CD! I could not believe the outcome. Here we had 92% of the file thrown away and the other 8% sounded like the original! So started a journey to learn not only to hear compression artifacts but also learning to be a "critical listener." What is a critical listener? I can look past the music and focus on it as an instrument would. I can isolate fidelity aspects much like someone lip reading can understand what you are saying without sound. Slightest changes are important and I know how to find and focus on them.
After some 6 months of non-step trial and error I all of a sudden realized that I could artifacts that others could not. And I became part and parcel of our signal processing team in evaluating any major changes to our audio algorithms. Those skills have remained with me and as I mentioned translate to finding small differences that others cannot.
Now you might say why we should care what a few trained listeners can hear. Well, unfortunately that is not the end of the story, pun intended. It turns out there are individuals in general public and audiophile circles that have the same critical listening skills. We were working with one of partner companies that was doing large encoding jobs for our end customers (electronic music distributors). One of their technical people was complaining about an artifact which we could not hear. He was local so we invited him to Microsoft. He comes over with his track and plays it for me and my codec team. We all look at each other and can't hear any issues. In amazement, he kept asking, "can't you hear this high-frequency artifact???" And our answer was no!
Being an important customer meant that we had to investigate it anyway. The codec team went to work and actually found and fixed the problem, proving objectively that he was wrong. And sadly for me, his ears and brain were better than mine. We hired him right away to work in our codec quality verification team.
Bringing us full circle, you are absolutely right that the types of distortions we talk about elude vast majority of listeners. Maybe all but a few. Having seen so many audiophiles, musicians, professional recording and mastering engineers fail these tests, I am well aware of difficulty of hearing such artifacts.
That is not the topic though. The topic is what standard bar of fidelity do we set that when we talk to someone else, we are confident they can't hear any artifacts there. In this instance, you questioned me and as I have demonstrated over and over again during many years, I am able to hear some of these artifacts. So I sure as heck am not going to brush the problems under the rug. Seeing how producing quality products doesn't cost much, that is what we need to do as a group.
What we don't want to do is go around and accuse people as corrupt when we haven't done our homework to understand whether they have the capability to hear things that we may not have.
Finally, let me say that as I have gotten older, I have lost a lot of my high frequency hearing. So I am probably nowhere as good as I once was. And others may be able to hear much better than me if they still have their full spectrum hearing. So let's make sure there is a nice safety margin beyond what I can hear. Again, it doesn't cost much of anything to do that.
