I wake up _super_ easy at many parts of the night, to all kinds of minor sounds. But when I lived directly behind a train, I not only don't recall it waking me

I wake up _super_ easy at many parts of the night, to all kinds of minor sounds. But when I lived directly behind a train, I not only don't recall it waking me up, I distinctly remember that, after getting used to it, it had a kind of calming effect on me. Really interesting. But I wonder if it was still disrupting my sleep and to what degree. I'd mainly like to know in case we have future housing options next to a train because, outside of being near horn / turns, I wouldn't normally worry much about it.