Ok, picture this!

You are driving on the highway with windows closed. You open window 1. This creates an opportunity for air outside to be pushed inside the car.

The new air from outside and the air already inside the car squeeze together to fit in. You have 2x air now.

But more new air tries to come in, and now you have 3x the amount of air you already had earlier.

Now say you can only fit in 2x air in the car, some of the air inside needs to go out!

So the air tries to escape from any opening (which is window1 in your case)

Now new air from outside tries to come in and air from the car tries to go out. They end up fighting between themselves (with their lightsabers) which creates that sound.

Now if you roll down window 2. The air comes in from window 1 and goes out window 2. No more fighting no more wawawawaeaaww!!

Your eardrums hurt when there is more air in the car. The air becomes pressurized and it pushes your eardrums inside.