Tympanogram
The tympanogram is the graphical representation of the measurement of the mobility of the eardrum during tympanometry . It shows the mobility of the eardrum as a function of the air pressure in the external auditory canal and thus provides information about the pressure and vibration conditions in the middle ear .
The Y-axis of the tympanogram shows compliance (mobility of the eardrum) in ml or in relative units. The pressure in the ear canal is plotted against the X axis in da Pa , and in older devices in mm H 2 O.
With normal middle ear function, the mobility of the eardrum is greatest when the pressure in the external auditory canal and the middle ear are the same; the maximum mobility of the eardrum is then around 0 da Pa . A negative pressure in the tympanic cavity (e.g. in the case of tube ventilation problems) results in a shift of the maximum into the negative pressure range. A middle ear is typically characterized by a flat tympanogram.
