ABSTRACT
The function of the middle ear is to convert pressure waves in the air to vibrations of the perilymph in the inner ear. Sound waves pass along the external auditory meatus striking the tympanic membrane which resonates faithfully in response. There are two middle ear muscles, the tensor tympani and stapedius. When they contract together the handle of the malleus and the tympanic membrane are pulled inwards and the base of the stapes is pulled away from the oval window. The auditory part of the inner ear is the cochlea, a bony canal 3.5 cm long, which spirals two and three-quarter turns around a central pillar, the modiolus. Cochlear amplification causes vibrations of perilymph that are transmitted to the oval window across the middle ear in the 'wrong' direction to the tympanic membrane which now acts as a loudspeaker producing otoacoustic emissions.
