Sorry to take so long to respond, but I had to think about this.
What I
assume is you mean something like what I do with coins and stamps, when examining them for some miniature, microscopic detail. Most people use maganifying glasses, but I don't have to, if I know what I'm looking for. "Focus," in other words, where one excludes all other "input" and "stimulus" so as to concentrate upon one tiny little thing.
Then I
assume you mean that it might be possible for a person to use the ears in the same manner, shutting out all else and focusing on just one sort of sound, or series of sounds.
So it might be that a conversation, even at low to moderate volume, could be heard at some distance, especially in an area with a lot of hard surfaces (few curtains or rugs to absorb the sound) such as the customer area of an automotive service business.
You would know more about that than I do, but I remain highly skeptical that with even the most-intense concentration, a person with hearing could "pick up" sounds that are usually too low and too far away, such as whispers and mutterings.
But really, I'm the last person here on conservativecave who'd know if that's so or not.
I've been complimented--oh God, s-o-o-o-o-o many times--for being such an interested, intense, "good" listener, but really, it's always a fraud, a sham, a masquerade.
When talking with a person, I go through the whole deal of shutting out all other happenings going on around me, focusing only and solely on that person. An intense, burning concentration that bores right through the other person. (Which presents no problems for decent and civilized people, who usually know and understand why that is, but liars and frauds avoid me like the plague.)
But really, it's physically impossible for me to hear what's being said.
And so what's actually going on is that I'm simply
imagining what's being said.
It's something I don't write about here, because it's one of the darker, most crippling, near-suicidal aspects of being deaf, and those are things best not discussed on a public message-board, excepting on Skins's island.
However, I've always been heartened by that apparently I "guess" pretty good. My writing's read by people in real life who've had conversations I've related in stories here, and they usually agree that, yeah, I got it right. Not perfectly, but reasonably, close.
And I suspect that hearing people too oftentimes imagine something's been said that wasn't said. They think they heard it, but what they "heard" is in their heads, not in reality.
And I imagine that the more deranged a hearing person (e.g., a primitive) is, the more likely it is that hearing person "heard" what it wanted to hear, not necessarily what was really said.
