What causes pressure disturbances ahead of the wing?
An approaching body needs to push air out of the way. Directly ahead of it, it will compress the air such that the local pressure increase will push the air out of the way. When the body is a lift-producing wing, the lower pressure on the upper side will suck the air towards it. So what can be observed are two effects:


Air gets compressed ahead of any body approaching at subsonic speed, the more the faster the body moves, and
When lift is created, this pattern will be distorted such that the flow will turn in the direction of the lift-producing suction.


The propagation speed of small pressure changes can be observed with your ears. Sound is just that: Small fluctuations in pressure. An approaching wing is just like an approaching siren, only that the siren emits an oscillating pressure variation and the wing an aperiodic one.

For the video my recommendation is


                
            

Note how the flow lines diverge ahead of the airfoil: This is where the flow is slowed down. At higher angles of attack you will also see how the flow lines bend up ahead of the approaching airfoil.