the eardrums are sitting in a tube that is connected to the nose and throat eustachian tube . normally the air pressure is equal on both sides of the eardrum , but the pop happens when the pressure changes either inside or outside your head as when you go up a mountain or go underwater or blow your nosethink of the eardrum like a lid on a plastic soda cup normally the lid sits flat because the air pressure inside the cup is the same as the air pressure outside the cup , but if you blow into the straw , you ' re increasing the air pressure inside the cup and the lid expands outward , if you suck air out of the cup , the pressure inside decreases and the lid sinks inward . so the cup is your head , the straw is the eustachian tube , and the lid is the eardrum