role in hearing

Last reviewed 01/2018

The main audiologic functions of the ear are:

• impedance transformation - the ossicles act as an impedance transformer, transforming vibrations in air - received at the ear drum - into vibrations in fluid - movement of the stapes footplate causing movement of the inner ear fluids

• sound amplification - due to:
• surface area of the tympanic membrane being 20x greater than that of the oval window
• lever effect of the ossicles

• protection - tiny muscles attached to the malleus and stapedius - tensor tympani and stapedius, respectively - serve to dampen vibration and protect the delicate structures in the inner ear against excessive noise

The middle ear mechanism works best when the pressure on either side of the ear drum is equal, ie, atmospheric. This is ensured by the Eustachian tube which connects the middle ear to the nasopharynx.

Eustachian tube dysfunction underlies much of the high prevalence of middle ear disease and hearing loss in children. During childhood, the tube becomes elongated with a slight downward angulation and thus, is more prone to blockage.