Figure 7. Representative impedance measures by tympanogram. The tympanogram types are as follows. Type A represents normal middle ear function. Type A curves have normal mobility and pressures and typify normal hearing and sensorineural hearing loss with normally functioning middle ear systems. Type B represents restricted tympanic membrane mobility. Type B curves have little or no point of maximum mobility and reduced compliance. This curve is very typical of a stiff middle ear system as is seen in otitis media. Type C represents significant negative pressure in the middle ear cavity. Type C curves have normal mobility and negative pressure at the point of maximum mobility, (negative pressure is considered significant for treatment when more negative than -200 mm H₂O). Type As represents normal middle ear pressure but reduced mobility suggesting limited mobility of the tympanic membrane and middle ear structure, commonly seen in fixation of the ossicular chain. Type Ad represents normal middle ear pressure but hypermobility. This pattern is indicative of a flaccid tympanic membrane due to disarticulation of the ossicular chain or partial atrophy of the eardrum.