I apologize if this is too basic of a question for this forum, but when having arm-chair discussions about the fluid dynamics of flute playing, a friend has said:
The lip-hole area together with the lung pressure is the cause of the pressure built in the mouth.
When measuring the mouth pressure you are already taking into account the lip-hole area and the lungs pressure.
My intuition is that this is incorrect--mouth pressure is caused by the "upstream" pressure in the lungs, and not any "downstream" container/flow size changes.
But intuition is often wrong in these situations--can anyone clarify the situation for us?