If you blow with a steady jet of air, you should make the ball hover in the air stream, without it falling to one side.

The high velocity supply air stream causes turbulence causing the room air to mix with the supply air.

This causes the air stream to either speed up or slow down, respectively.

This provides focus to the player's air stream and thus to his/her sound.

To be louder, a flute must use a larger resonator, a larger air stream, or increased air stream velocity.