An Introduction To Admittance And Impedance

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Immitance is a general term to describe admittance and impedance. Impedance is the measure of opposition to energy flow (sound) into the ear at the plane of the tympanic membrane. Admittance is the total energy flow through the vibrating system. Immitance audiometry is a test battery using acoustic impedance or acoustic admittance to estimate hearing sensitivity and function of the middle ear system. Impedance is typically measured as compliance now. Tympanometry is the test battery for measuring the compliance of the ear in equivalent volume across a range of pressures. It provides an estimation of hearing sensitivity and middle ear function in relation to ear canal volume, compliance, and middle ear pressure.
To perform an
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If the pressure is not within that range, it could suggest Eustachian tube dysfunction.
The compliance, or mobility, of the tympanic membrane is also noted as a tympanometric compliance value. Compliance is measure in cubic centimeters (cc) or milliliters (ml). The point on the pressure scale where the maximum compliance occurs is essentially equal to middle ear pressure of the ear tested and is known as the point of maximum compliance. The peak compliance should be within the range of .2 cc to 2.0 cc. If the compliance is considerably lower than .2 cc, it may lead to a diagnosis of tympanosclerosis or otosclerosis; however, if it is much higher than 2.0 cc, it may imply ossicular disarticulation or a hypermobile tympanic membrane.
Compliance is plotted over a range of pressures on a tympanogram. There are five possible types of tympanograms that may result from the test: type A, type As, type Ad, type B, and type C. A type A tympanogram suggests a normal conductive system functioning. The peak pressure is noted within the normal range (-150 daPA to 50 daPa) and the point of maximum compliance occurs within a normal range (.2 cc to 2.0 cc), as well. The ECV should also fall between .65 cc and 1.75 cc. There is no indication of a middle ear pathology if a client receives a type A tympanogram. It is important to note that this test battery is not designed to detect a sensorineural hearing loss, because it solely reports outer and middle ear functioning.
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