Impedance matching is the middle-ear mechanism that amplifies sound pressure.
It compensates for energy lost as sound passes from the low-impedance air medium to the high-impedance fluid of the inner ear.
Without this amplification only about 0.5% of sound energy striking the oval window directly would reach the endolymph, since about 99.9% of energy is reflected at an air-fluid interface.
Structural Basis and Values
Sound vibrations reach the inner ear through the ossicular chain:
Vibrations of the tympanic membrane pass through the ossicular chain (malleus, incus, stapes).
They reach the footplate of stapes at the oval window.
This transmits them to the perilymph of the inner ear.
Middle-ear structures and impedance-matching values