|Coronal section of right temporal bone. ("Tympanic antrum" labeled at upper left.)|
|The medial wall and part of the posterior and anterior walls of the right tympanic cavity, lateral view. ("Mastoid antrum" labeled at upper left, in dark circle.)|
|Gray's||subject #230 1042|
The mastoid antrum (tympanic antrum, antrum mastoideum, Valsalva's antrum) is an air space in the petrous portion of the temporal bone, communicating posteriorly with the mastoid cells and anteriorly with the epitympanic recess of the middle ear via the aditus to mastoid antrum (entrance to the mastoid antrum). These air spaces function as sound receptors, provide voice resonance, act as acoustic insulation and dissipation, provide protection from physical damage and reduce the mass of the cranium.
The mastoid air cell system is a major contributor to middle ear inflammatory diseases. 
- SUNY Figs 30:02-01 - "Illustration of the continuity of the nasopharynx with the middle ear cavity via the auditory tube."
- Mastoid+antrum at eMedicine Dictionary