There is air in the drum room, because there is

The eustachian tube is very important for regulating the air pressure in the middle ear. When we chew and swallow, the eustachian tube will open and close in time to let air in or out, so as to keep the air pressure in the middle ear consistent with the outside world.

The role of the tympanum is to transmit sound into the inner ear, amplify sound, adjust the sound size, and maintain the air pressure balance inside and outside the tympanic membrane. The tympanum is the most important part of the middle ear, surrounded by the petrous part, scale part, tympanic part and tympanic membrane of the temporal bone, almost parallel to the sagittal plane.