Consider the following situation, also depicted in the picture bellow (and please excuse my lack of Paint skills):
A helicopter is flying at a constante altitude, and hovering the same ground spot. The helicopter is not air tight, and it even has an open window.
On the inside of the helicopter there is a box, with a small hole on the side. Except for this hole the box is air tight. Inside the box there is an air pressure sensor.
A plane, flying at a higher altitude than the helicopter, drops a box exactly like the one on the helicopter.
When the two boxes are at the same height (one sitting still on the chopper and one falling) how do the pressure sensor readings differ from each other, considering the Bernoulli principle? If the pressure readings differ, can they be used to estimate the fall velocity of the box?