It's selective filtering, not just speech vs background noise
Many classically trained musicians can attest to having spent hours in practice rooms concentrating on sounds we produced while ignoring the cacophonies from adjoining rooms. We didn't have sound-proof cubicles when I was young, just renovated dormitories with little more than plaster board for walls. Two pianists wall-to-wall were especially fun.
I found that I studied for tests and completed assignments better in noisy places (food malls, busy lobbies, etc.). Quiet places just make me sleepy.
Unfortunately, I've always had a 75% hearing loss in one ear so I have to turn my good ear in the direction of the sound origin.
I wouldn't say that musicians have better hearing, they just might be more practiced at certain sound processing tasks.
