I'm probably not qualified to reply to this but my thoughts are that It's certainly possible to enhance your hearing in a similar way to boosting your peripheral awareness with photo-focus.
There are several meditative listening techniques I've tried such as focusing on only sounds near to you and then only sounds far away & alternating between the two - this is called "ranging" I think. Also, tuning into multiple conversations in a coffee shop. It's about becoming aware of what your conscious mind normally filters out as noise.
I've also had some success with a language course that had a meditation/relaxation step prior to listening to the tapes, followed by activation by combined audio/visual re-iterations.
As a musician, I'm conscious that different people are stimulated to very different degrees by audio input and I believe those who are less responsive are so due to nurture rather than nature. I would say it's entirely possible for everyone to learn to improve their audio perception and to use pre-conscious hearing (normally filtered noise) to absorb and learn.
I guess that's why subliminal audio advertising was banned in the same way that 1-frame video advertising was. Do people still play their records backwards? lol
btw - Have you seen "pzizz"? It's a relaxation device/audio-software that amongst other things involves subtle soundscapes offset at different frequencies in each ear - the frequency differential intended to induce 'beats' between the ears which stimulate alpha/beta/theta brainwaves (depending on beat frequency) to enhance relaxation. If this works then it is surely inducing the accelerative learning state?
Interesting question.
