As for the matter of “hearing the sound of wind and water,” this means being calm and quiet on the surface while keeping energy agressive underneath.
Wind has no sound; it produces sound when it strikes objects.
Water also has no sound when it is falling from above; it makes a frantic sound below when it comes down and hits things.
Using these images as illustrations, the point is to be calm and quiet on the surface, while keeping energy aggressive underneath.
Movement is yang, stillness is yin. Yin and yang interchange, inside and outside. When yang moves inwardly, you’re outwardly still, in the yin mode; when you are inwardly yin, movement appears outwardly…This is in accord with the pattern of Nature.
Beating the Grass to Scare the Snakes: When an opponent is startled and the sense of opposition is distracted, the opponent will experience a gap in reaction time.