Impedance denotes -
Site of perforation
Disease of cochlea
Disease of ossicles
Higher function disorder
“Impenance audiometry, measures the resistance of tympanic membrane and middle ear and also compliance of tympanic membrane and ossicular chain to sound pressure transmission. Tympanogram is the graphic representation of compliance and impendance of tympanic osscular system with air pressure changes.”
From above text it is quite obvious impedance is for disease of ossicles.