The frequency used in tympanometry is:

Ref: Diseases of the Ear. Nose and Throat by PL Dhingra 5th edn .2010 page 29Explanation:It is a part of Impedance audiometry (la)Other part is acoustic reflex measurementsTympanometryBased on the principle that when sound strikes the tympanic membrane some energy is absorbed and some is reflectedin this we measure the reflected sound and its variation with changes in EAC pressure, which is plotted as a graph called tympanogramTells us status of middle ear Types of curves are as followsA type - Seen in normal individualsB type - It is a flat curve and is seen in presence of fluid in middle ear like SOM, thickened tympanic membraneC type - Maximum compliance occurs with negative pressure and is seen in retracted TMAd type - High compliance at ambient pressure. It is seen in ossicular discontinuity or a thin and lax TMAs type - Compliance decreased at ambient pressure. Seen in fixation of ossicles (otosclerosis). (See figure below)