Ok, so it sounds gross, but i once had a massive build up of earwax. Like peanut sized, one in each ear. They blocked out a lot of sound.
I had these for a while. I refused to see a doctor, because i hate going to the doctors. Partially out of embarrassment, money, and general disliking.
So anyway, i had this for quite some time, until i eventually swallowed my pride and got them flushed out by my GP once a regular conversation in a busy place became much more difficult than it ought to be.
The amount of sound that i had been missing out on, which flooded back to me, was amazing. I heard weird things that i had never heard before. Little things like rustling outside or the brushing of my feet against the carpet.
What im trying to say is, i know what you mean.
Oh also, i once attended a university lecture on how your mind blocks out certain sounds when you get used to them, to an extent that you can't hear them even if you tried.