And that sounds all well and good. It seems like the kind of thing your brain ought to be doing. But then again, it also means that you are missing most of the moment. That "noise" isn't actually noise, it has meaning. Things are happening around you, and your mind is letting you miss it.
I'm not saying it's a bad thing, I'm just saying it's significant.
Your brain is trying to find things of significance. Things that you can't interpret aren't of significance. Thus there may be many things, even important things, that your mind is writing off as noise-that get tuned out completely.
To illustrate my point, consider the following:
Now in this particular case it is a physical limitation, not mental, that's blocking the relevant information. (If you can't read the above image, it says "Colorblind people are awesome.") But we're still dealing with the same conceptual animal. This image contains a whole band of data that some people simply can't interpret.
And when you miss layer of the world around you because you weren't well-educated enough, emotionally sensitive enough, or culturally aware enough, the limitation is no less real.
*Except sometimes you do pick up a word or two, which makes me think that your mind is also scanning all that noise. I've often wanted to do experiments where I'd go into a crowded place, softly-but-clearly say various dirty words, and see how many heads I can get to turn.