Impedance Audiometry
If measures the integrity of the middle-ear system. This test gives easy, quick and objective measurement of resistance of TM, middle –ear and compliance to round pressure transmission. 
 

Impedance Audiometry involves 2 tests: -
a)  Tympanometry: Variable air-pressure is introduced into the sealed auditory canal. The air pressure of M-ear cavity and mobility of TM and assicular-chain can be determined. These are plotted as a graph called Tympanogram. 5 common types of curves that can occur are:
I.   A-> Normal
II.  Ad-> Placid TM / O.C discontin
III. As-> Otosclerosis
IV. B-> Serous Otitis Media
V.  C-> Eustachian obstruct

b) acoustic reflex measurement
During auditory Stimuli the changes in compliance due to contract of M-ear muscles ie; stapedius and tensor-tympani are noted. These reflexes are elicited 70 dB above hg threshold.