audiological survey of normative data in zagazig population

impedance audiometry is one of the advancedaudiological tests applied in the field of audiology.Its principle is based on the acoustic impedancewhich is the resistance offered by the conductivesystem of the ear to an acoustic signal. In normalear Borne of the acoustic signal is absorbed to themiddle ear and the rest is reflected back at thetympanic membrane. The amount absorbed and thatreflected depend on the compliance and the resis-tance of the conducting system, that is to say tympanicmembrane, ossicles and ligaments. By knowing thecompliance and the impedance of the normal ear, wecan detect any shift from the normal.The instrument used in these measurements isthe Electroacoustic impedance dridge.Change of pressure in the ear canal and contrac-tion of the intratympanic muscles change the impedance.