Die Impedanzmessung ist eine Hörprüfungsmethode zur Beurteilung der Mittelohrfunktion (sog. Tympanometrie). Durch Messung der Reflexschwelle des M. stapedius ergeben sich außerdem diagnostische Anhaltspunkte, z. B. zur Unterscheidung zwischen Innenohrschwerhörigkeit und neuraler Schwerhörigkeit, zur Topodiagnostik neuraler Hörschäden und zur Funktionsprüfung des N. facialis.

The portion of a definite sinus tone signal, which is reflected by the eardrum, is an expression of the acoustic impedance of the tympanic membrane and can be measured by means of an electroacoustical bridge. A controlled change of the air pressure in the external auditory canal streches the eardrum, thus causing a change of impedance. The continuous record of this impedance change (so-called 'tympanogram') represents the compliance of the tympanic membrane and the ossicular chain. The acoustically evoked contraction of the stapedius muscle - in this film cinematographically in vivo documented for the first time - can be proved by recording the impedance change by this muscle contraction. Tympanometry and measurements of the stapedius reflex support the differential diagnosis of condutive hearing loss with an intact tympanic membrane. In a defect eardrum the function of the Eustachian tube can be examined by means of the air pump of the impedance measuring apparatus.The measurement of the stapedius reflex threshold alone serves as an objective hearing test and assists the differential diagnosis of sensory and neural hearing impairments as well as the functional analysis of the paralyzed facial nerve.