In the 1.13 update mojang added a lot of ambiant sounds underwater, wich make living / exploring underwater much more rich and pleasant.
I think they should go futher with this idea and add more ambiant sound outside water too, here are a few examples:
- Wind soun when high in the air
- Wind making noise with the leaves of the trees in forests
- Constant caves sounds underground (just like in the water)
- More sound coming form far away, maybe sounds of animals or even brids