On the night that I became aware of the quality of the train noise, clickety-clack, clickety-clack, clickety-clack, I did not actually know the word "qualia". At that time of my career, I haven't done much research into the phenomenological dimensions of this universe. I was simply trained as a physicist, with some diversions into biology. The encounter with the word itself came a few months later, when I was reading a book on neurophilosophy. Only then did I realize that the problem that I bumped into was quite an old one, occupying the minds of philosophers and philosophically oriented people for many years.
Although I did not know the word "qualia", as I listened to the train noise, it became suddenly clear to me that the approaches of the physical sciences, in which you try to describe the events in this world in terms of numerical equations, cannot be applied to the origin of the quality of the noise that I was listening to. You may be able to Fourier-transform the sound waves, and discuss the frequency spectrum. That kind of logic, however, would not explain the origin of the phenomenal quality of the sound that was reaching my consciousness. It was clear that, there was a "hole" in the physical description of the universe as we know and experience it. And the hole was rather large once you notice its existence.