Alphonse, thanks for a very good posting. I wanted to reply something similar but couldn´t have been as thiughtful as you were.
There are parts that I agree to and parts that I don´t, at least not in total.
Well, I don't agree with this sort of mainstream youthism. To me, a beautiful couple is a couple that radiates tenderness, humor and love. This is visible but is also reflected in sounds. It has nothing to do with age.
Similar to what I wanted to say. Beauty is not a matter of age, at least not in first place, even if you are eye-minded like me and most of the guys. But to some extent it depends on your own age. I did not think of women over 40 or even 50 as beautiful ladies when I was 20 myself.
What I see as ugly, and therefore unpleasant to hear, is sex with brutality, selfishness, no respect for the partner. Sex doesn't sound good, when lie, simulation, power, money are involved. That's why most porn movies have awful sound tracks, just because they are all about these.
Totally agree, nothing to add.
Moreover, older people often have better sex, because they learned to care for the others' expectations. They have time and nothing to prove.
That´s kind of mainstream seniorism

You don´t need to be old to have learned this. I know you did not claim the opposite.
Why only the girl? Should girls be afraid of getting older while men have no problem with that? Isn't that an unfair dictatorship on girls?
I´d say this is simple to answer (and I disagree on this point). As a male being, you are usually interested in girls, especially when it comes to fantasies. And fantasies is what listening to sexsounds is all about. So for our fantasies it is more important that the girl is one that you´d like to have sex with yourself.
I would even go so far as to say that a beautiful girl with a not so beautiful guy is even better for my fantasies. Call me dopey but what comes to my mind is, if she has sex with him, she would take me too. Sounds strange? Sure it is, but this is how my brain works. And hey, I´m still talking about fantasies.
In real life, in a relationship both partners should try to keep their attractiveness for each other of course, whatever they define as attractive.
Or is it that men, when getting older, try to prove to themselves that they are not affected by age, by going with girls who could be their daughters?
This might be true for many men but it is definitely not the whole truth. Says the man who is chatting to a woman 19 years younger and she´s the one who doesn´t want sex partners of her age (not that we are). But she made me think about the pro and cons and there are more than just a young body or to prove that I´m not affected by age.
It is always a bit risky to discuss in a language that is not your mother tongue, at least for me it is. But I hope my reasoning doesn´t sound too silly.