A consistent authority on sound is someone who can consistently nail different attributes in a blind comparison.
It's not just high frequencies with age, a lot of detail/resolution comes that at a band much below and older ears just don't hear it. There are also genetic differences, some people just hear better than others.
I was in a room with the late Ken Ishiwata (Rotel's former soundmaster) when he could consistently nail even changes in different hires sample rates, which was impossible for a couple of us in the room to do..He must have been early 60s at that time. That's a unique kinda guy...Yamaha, TAD, Technics, etc have soundmasters who have such capabilities. It's their livelihood, they are of a different caliber, built/forged a certain way.
Fremer, Guttenberg, etc are not the caliber of guys who fall in such a category..
There are others, some professionals who are tied into the mastering process, etc...there's a woman i know, quite unbelievable....There are instrument enthusiasts, etc that i've known who may fall in a similar category as well.
I am in my mid 50s. I don't presume to be the same as above mentioned folks on different attributes they can distinguish. But, i spent 45+ years with a couple of instruments. If anything is off on their sound, it is as obvious as night and day to me. For example, i have 4 violins. 2 of them sound might sound the same to a non-violin player. The difference is night and day to me..it's one thing i know....You give me another instrument, let's say a sax. I have a very friend who's an amazing sax player. You ask me something about his instrument, something doesn't sound right on his instrument or not? I am 0% expert there...can't ask me that..It's ok to admit when you're not an expert of something...that someone else is an expert on...
Other conditiions exist as well... Ever hear of synesthesia? It's technically a health condition, but, i hear/experience sound very differently than some others because of it. Things they may not hear i can hear it and its not entirely auditory either, its something else.
But, there are very simplistic statements made by these measurement type of guys that everyone hears or not within the same threshold based on some very coarse auditory test...it's a bit foolish to be in the latter camp.
@newton_john wrote
You are repeating a prejudice about ageing. We all lose our ability to hear high frequencies with age. This does not affect our appreciation of music per se because that is dependent on our ability to distinguish tiny timing differences between harmonics. Our ability to hear these timing differences does not necessarily deteriorate with age to the same extent as with high frequencies. You are slandering Michael Fremer along with all older people.