Ambient sounds will play depending on the biome, time and other situational factors.
In a forest during the day birds chirp, leaves blow, etc
In a forest during the night leaves blow, crickets (cricket?), etc
On top of a really tall mountain wind blows heavily.
In a cave every sound will be very reverberated.
I think it could add a bit more of an atmosphere to the game to have not just the visuals of the world change as you explore, but also the audio.