My hearing falls off a cliff at high frequencies. Combine that with acute bilateral tinnitus and little beeps and squeaks might as well not exist for me, stuff like battery-powered smoke detectors, the continuity beep on a multimeter, etc.. I don't hear them unless the environment is dead quiet.
I'm in the same camp as above with background noise. Any at all and I lose details, especially if someone is speaking to me. I'm fine if I can see their mouth. Otherwise, bupkis. SWMBO double-hates it because she not only has a soft voice, she's one of those people who speaks up by speaking softer (more intensity, but as an almost-whisper). It's extra bad when we're traveling, what with road noise and having to keep my eyes on the road.
Weird thing is, if everything is quiet, I have extremely sensitive mid-and low-frequency hearing. I can hear our washing machine indicator from out in the yard or understand a spoken conversation from across the room. But, again, it has to be quiet. Any background noise, even the rustling of leaves, and it's game over.
Brad